Network

Network + Training & Test Preparation Guide

Peer-to-Peer Networking In a peer-to-peer network there are no separate computers that act as servers. All of the computers on the network can act as either clients or servers depending upon the needs of the user. This type of network is most often used when fewer than ten computers are involved. A peer-to-peer network is simple and inexpensive to install. The computers are simply cabled together, and as long as each computer has an operating system capable of client/sharing (e.g. Windows 95 and up) they will be able to communicate via the network. In a peer-to-peer network all computers are equal. A disadvantage of the peer-to-peer network is that since users are responsible for their own systems’ security, network security is unreliable. Also, a peer-to-peer network is difficult to expand.

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Chapter 1 – Networking Fundamentals

Basic Network Structure (Topology) A network’s basic structure, or topology, refers to its physical layout, design, map, scheme, or diagram. As a network professional, you will need to know how to choose the network topology that will best suit the needs of your network. The type and capabilities of the equipment that will be used, future growth needs, and how a network will be managed are all potential problems that need to be considered when planning a network. Setting up a network requires more than just cabling the computers together. Different topologies have different cabling requirements. NICs, (Network Interface Cards, also called Network Adapter Cards), connectors, how the computers will talk to each other (protocols), and even how the cabling is run through a building, are all determined by the topology used. There are three standard topologies that a network professional needs to understand: •

Bus Topology

•

Star Topology

•

Ring Topology

Bus Topology The simplest and probably the most used form of network topologies is the Bus topology (sometimes called a linear bus). The nodes (computers or devices connected to the network) are all connected along a single cable. This cable is called a trunk, backbone, or segment. Devices on a Bus topology communicate by sending data to a specific address on the network (a device’s address). An electronic signal is sent out on the cable to all of the devices connected on the network. However, only the device whose address matches the address encoded in the signal will respond to the signal. Only one computer at a time can transmit data on a Bus network or signals will collide and the transmission will fail. This means that the more computers that are connected to a Bus the slower the network becomes as devices are waiting to transmit or retransmit. The Bus topology is a passive topology. Devices only listen for data being transmitted, they do not move the transmissions along. The signal is sent out on the cable and it travels from one end of the cable to the other. If not prevented, the signal would travel back and forth along the cable and cause what is known as signal bounce. While the signal is bouncing back and forth, it prevents other devices from sending data. To stop signal bounce, a component called a terminator is installed at each end of the cable. A terminator absorbs the signal and stops signal bounce. In a Bus network, if the cable breaks, the network will go down and devices will not be able to communicate with each other.

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Network + Training & Test Preparation Guide

Star Topology In a Star topology, all devices are connected to a central point called a hub. It requires a lot more cable than the Bus topology, but the advantage is that if one computer (or the cable that connects one computer to the hub) goes down, the rest of the network will still continue to function. If the hub fails, however, the entire network will go down.

Ring Topology In a Ring topology, the devices are connected in one continuous circle of cable. There are no ends to terminate. The data is transmitted around the loop in one direction and passes through each computer on the network. The Ring is not a passive topology like the Bus topology. The signal is actually boosted and sent on along the cable when it passes through the computers on the network. A disadvantage is that if one computer fails, it can affect the entire network.

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Chapter 1 – Networking Fundamentals

With IBM Token Ring networks, the ring is actually in a special type of hub called a Multistation Access Unit (MSAU). In these networks, a computer can fail and not prevent the network from functioning. Special Topologies In addition to the above topologies, today’s networking professional will encounter many network topologies that are combinations of the above configurations. These are known as Hybrid topologies. Before you can understand some of these special topologies, you will need to know the difference between a physical and a logical topology. So far, we have been discussing physical topologies. These are the methods in which a network is actually wired. You will be able to see a physical topology. A logical topology, on the other hand, is how the network actually works. For example, some Ethernet networks today are wired using a using multiple hubs. This gives us a physical star topology. However, they operate between the hubs like a bus topology and are therefore a logical bus. Also, Token Ring networks are physical stars and logical rings. Hybrid Topologies The Star Bus topology is a hybrid of the Star and Bus topologies. It consists of several Star topology networks that are linked using linear Bus trunks. The Star Ring topology is similar to the Star Bus, but the hubs in a Star Ring are connected in a star pattern by a main hub. Mesh Topology In the Mesh topology every device is connected to every other device by separate cables and has redundant paths. This is very expensive to install but it is extremely reliable because of the redundant paths.

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Network + Training & Test Preparation Guide

Wireless Topology A Wireless topology is one in which there aren’t any cables connecting the network devices to the LAN or one which the LAN uses wireless technology between access points. Since each computer has its own connection to the wireless access point (WAP), the topology of a wireless network is that of an “invisible star”. . The benefits of wireless technology will be discussed at length in Chapter 4 of this book.

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Chapter 1 – Networking Fundamentals

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Network + Training & Test Preparation Guide

Network Access The topologies that we have been discussing describe the way in which the computers and other devices on a network are connected. This is based on the media or wiring of the network. Another aspect of networks that is related to topology is the way in which the network is accessed by individual devices. With several devices connected to one media, we create kind of a “party line”. The method that is used for an individual device to be able to use the network party line is called media access. The two most common network standards are distinguished by their respective media access methods, they are called Token Ring and Ethernet. We will also cover access methods in more detail in the chapter “Network Protocols and Standards.” Token Passing Token passing is the method of sending data around a Token Ring topology. A token is passed along from device to device until it is received by a computer that needs to transmit. The sending computer grabs the token and encodes it with addressing information for the receiving computer and sends it out on the ring. It is passed along from device to device until it arrives at the computer whose addressing information matches the one encoded on the token, and the message is delivered. The receiving computer then sends the token back to the sending computer to let it know that it received the message. The sending machine then creates a new token to send around the ring that will be grabbed by the next device that wants to transmit data on the network. Since there is only one token, only one device at a time can communicate on the network.

Ethernet Ethernet uses a system known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Carrier Sense means the network card listens to the cable for a quiet period during which it can send messages. Multiple Access means that more than one computer 26

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Chapter 1 – Networking Fundamentals can be connected to the same cable. Collision Detection is the ability to detect whether messages have collided in transit (neither message will arrive at their destination and both will be retransmitted).

Collision Detection Fast Ethernet Fast Ethernet was developed to meet the increasing demands on networks. Fast Ethernet works on the same principals as Ethernet but operates at 10 times the speed of the original. Ethernet transmits at 10 Mbps and Fast Ethernet transmits at 100 Mbps.

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Network + Training & Test Preparation Guide

Hubs and Concentrators More and more networks are using hubs and they are pretty much standard equipment in today’s networks. Today, hubs come in a variety of names depending on their function. The most common name used with Ethernet is a hub or a concentrator. With a Token Ring, they are called MSAUs (Multiple Station Access Units). Essentially, they are all the same, since they provide a common location for connecting the cabling of a network. Just remember, not all hubs are the same and you must use one that is designed to meet the needs of the network. Hubs can be classified as either passive or active. Passive Hubs A passive hub acts as a connection point only. Signals pass through the hub but are not regenerated or amplified. Passive hubs do not require any electrical power to function.

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Chapter 1 – Networking Fundamentals Active Hubs Most of the hubs used today are active hubs. An active hub regenerates or amplifies a signal when it is passed through. This type type of hub requires electrical power to function.

Hub-Based Networks Hub-based networks are increasing in popularity. They have many advantages over other types of networks: 1) If a cable breaks only the portion of the network on that segment is affected. 2) Centralized monitoring of traffic and activity along with diagnostic capabilities are available. 3) A variety of cable types can be accommodated. 4) Expanding the network can be easily accomplished by using hubs.

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Network + Training & Test Preparation Guide

Summary In this chapter we learned that the main reason for networking (as it relates to computers) is the sharing of resources. The two types of networks are LANs and WANs. A LAN is the smallest form and is the basic building block for larger networks. A WAN is not geographically limited and typically has greater speed of communication than a WAN, and the Internet is the world’s largest WAN. We also learned about the two basic network classifications of networks: the peer-to-peer network and the server-based network. It is important to know the differences between these two classifications and the advantages and disadvantages of each. Topology is a term we use to describe the logical shape of the connection of computers in a network. The three main types of topology are bus, star, and ring. Be sure to complete the following exercises and review questions. If you are having trouble with any of these concepts, go back and review the chapter again.

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Chapter 1 – Networking Fundamentals

KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword

Definition

Active Hub Application Application Server Bus Topology Client Data Fax Server File Server Hub Hybrid Topology LAN Mail Server MAN Media Mesh Topology Network Network Administrator Passive Hub Peer-to-peer Peripheral Print Server Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide

Keyword Resources Ring Topology Security Server Server-based Sharing Star Topology Token Passing User WAN Wireless Topology

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Definition

Chapter 1 – Networking Fundamentals

Review Questions - Chapter 1 1. What are the key differences between a local area network (LAN) and a wide area network (WAN)?

2. What is the main reason for networking computers?

3. What is a “sneaker net”?

4. Name some advantages of having centralized documents.

5. What does MAN stand for and why is it no longer in use?

6. Name some advantages of a Peer-to-Peer network.

7. Name some disadvantages of a Peer-to-Peer network.

8. Name some advantages of a Server-based network.

9. Name some disadvantages of a Server-based network.

10. Name the three basic topologies.

11. What is the difference between a physical and logical topology?

12. Name two media access methods.

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Chapter 2 – Network Operating Systems (NOS)

Chapter 2 - Network Operating Systems (NOS) Up to this point we have focused on the design aspects of networking. Even if you have the best network design composed of the best hardware in the universe, if you don’t have the software to run it, it is just a pile of metal and plastic. You can get it all set up and turn on the power, but without an operating system, it will just sit there. This chapter is all about the various operating systems with which a networking professional needs to be familiar. When we are talking about operating systems, what we are really talking about are network operating systems. Network operating systems (NOS) are specialized operating systems designed to integrate computers in a networking environment. Most of today’s client and server operating systems have a built-in network operating system. When we refer to the operating system in this chapter, we are referencing the built-in network operating system component. In this chapter we will explore the features and benefits of the more popular network operating systems. We will also discuss their minimum requirements and interoperability capabilities. The differences between server and client operating systems as well as preemptive and non-preemptive multitasking will be covered as well.

What is an Operating System? Not that long ago, network operating systems were designed to operate on top of an existing operating system. A computer needed two sets of software in order to function in a networking environment. Today, most networked computers run software that was specifically designed to run both the computer’s stand-alone functions as well as its networking functions. Hardware resources such as RAM, processor time, hard disk space, and peripherals are all controlled by the operating system (the software). The operating system is also responsible for the running of applications (e.g. word-processing, spreadsheet, and database programs). The main objective is to make sure that the hardware and the applications are all compatible with each other, as well as the operating system.

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Network + Training & Test Preparation Guide Preemptive vs. Non-preemptive Multitasking Multitasking, put simply, means that an operating system has the ability to perform more than one task at a time. A true multitasking (multi-processing) operating system is able to process as many tasks as it has processors. Most operating systems appear to be performing multiple tasks by alternating between tasks until they are all completed. Preemptive multitasking means that the operating system can take control of the processor without a task’s permission. Non-preemptive multitasking is when the task decides when it is done with the processor. In non-preemptive multitasking, the processor is never taken away from a task. Preemptive multitasking began with Windows 95 and the Intel Pentium processor. It is used on all of the latest operating systems.

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Chapter 2 – Network Operating Systems (NOS)

What is a Network Operating System (NOS)? A NOS is an operating system that includes other software, such as BSD UNIX, Novell NetWare, Microsoft Client, or a similar program, to communicate with other computers over a network. Peer-to-Peer LANs Many smaller networking environments utilize the peer-to-peer network configuration. Peer-to-peer LANs are an excellent choice for the network that has less than ten computers and no need of security (such as a small office environment). It is certainly the most economical of the networking choices. Usually only NICs and cabling will need to be purchased to implement this kind of network. A peer-to-peer LAN is not a client/server-based network. Instead, each workstation may act as either a client or a server depending upon whether it is accessing resources on another workstation or if another workstation is accessing its resources. Usually this type of network only shares files and peripheral devices. Most of the operating systems in use today are already capable of managing this type of network. Windows 95/98 Windows 95 and Windows 98 are operating systems that include a network operating system. Their new graphical interface and networking capabilities make them a vast improvement over their predecessors. They use an icon called the Network Neighborhood for desktop access of the network. All shared resources are arranged on a hierarchical basis and displayed in Network Neighborhood. Plug-n-Play technology has also made installing a NIC much easier. Windows 95/98 is also able to better identify NICs. To install a NIC with Windows 95/98 is as simple as installing the card, turning on the computer and answering questions. Then, all you have to do is share any directories and peripherals to the network, and you have a working network. Windows 95/98 also performs very well as a client with both the NetWare and Windows NT operating systems. It is necessary to install the requester software (NetWare Client32 for Windows 95) with NetWare. With NT the only drawback is that you will not be able to utilize NT’s advanced security features because Windows 95 is not compatible with the NTFS file system. Windows ME Windows ME is the client operating system that has followed the Windows 9x operating systems. It is well-suited for editing home movies, moving photos to the Web, and archiving music. It protects critical files and will allow you to revert your system back to normal if anything goes wrong. Help and support is improved from Windows 98 and home networking is made easier than ever.

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Network + Training & Test Preparation Guide Windows 2000 Professional Windows 2000 Professional is the client counterpart to Windows 2000 server. It features file protection, driver certification, remote OS installation, multilingual support, peer-topeer support for Windows 9x and NT, EFS (Encrypting File System), IPsec and Kerberos support. It also supports Microsoft Management Console (MMC) and group policies. Windows XP Home Windows XP Home edition is the newest edition of Microsoft’s OS for home users. It allows for faster user switching, a simplified visual design, It also uses System Restore, like ME, which allows for safety when installing additional software or making changes to the computer’s configuration. It, like the rest of the client OS software mentioned here, is equipped to be networked easily. Other Peer-to-Peer LANs The following table lists other peer-to-peer LAN software and their manufacturers that the networking professional may come across in real life but are unlikely to be on the test:

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Chapter 2 – Network Operating Systems (NOS)

Software Name

Manufacturer

10NetPlus

Digital Communications Associates, Inc.

AppleTalk

Apple Computer

Easy Net

LanMark

GV LAN OS

Grapevine LAN Products

LANsmark

D-Link Systems

LANsoft

ACCTon Technology

LANStep

Hayes Microcomputer Products

LANtastic

Artisoft

NET/30

Invisible Software

Network OSCBIS

Peachtree

OS/2 Warp

IBM Corporation

Personal NetWare

Novell

POWERLan

Performance Technology

ReadyLink

Compex

WEB

WebCorp

Server/Client Software In a peer-to-peer network, the computers act as both a client and a server. However, it is necessary to have an operating system that can perform in this environment. In a Serverbased network, the purpose of a network operating system is to connect all devices on a network (computers and peripherals) and to coordinate their usability. This can also provide accessibility and security for all devices on a network. Some network operating systems require that different versions are installed depending on whether a computer is the server (provides resources remotely over a network) or a client (uses resources locally).

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Network + Training & Test Preparation Guide There are two types of networking software that must be considered: •

Client Software

•

Server Software

Client Software If you type a command for your stand-alone computer to perform a task, the command is processed over the computer’s internal CPU via the computer’s local bus. However, if you were requesting resources or services that exist on a remote server, the operating system has to have the capability to redirect (forward) the request away from the local bus, out onto the network, and to the server. The component that handles these requests is called the redirector. Server Software As their name implies, Servers exist to serve. They process requests from clients for resources such as files and peripherals. They are the storage facility for the bulk of the data in a network environment and as such are an excellent point from which to centrally manage a network. Unlike most client software, server software includes services for the following: •

Managing User Accounts

•

Security

•

Data Protection

Managing User Accounts Servers make it possible to manage users from a central location. Users are required to enter a password before they can log on and gain access. Administrators set up and manage user accounts and passwords. Security Administrators can set up the accounts to determine who gets privileges to what resources and change them as needed (including denying access). The server keeps track of who is logged onto a network and what resources have been (or are being) accessed. Network security is discussed in greater detail in Chapter 10. Data Protection As we already discussed, most of the data is stored on the server. This makes it an excellent point from which to perform regular backups. Most network administrators provide some sort of fault-tolerance system on the server. At the very least, the server should be attached to an uninterruptible power supply (UPS). Some networks even cluster server so that more that one server can share a database of information. This 40

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Chapter 2 – Network Operating Systems (NOS) provides for load balancing of the server resources as well as fault tolerance if one server were to fail. The Redirector (Requester) The redirector (in Novell NetWare this is called the requester) is responsible for forwarding requests away from the local bus and redirecting them to the server. Basically, it is a section of code located in the network operating system that intercepts requests and determines if they are local requests, or if they need to be redirected to the server. The purpose of the redirector is to make network resources look like local resources to application programs. It does this by assigning drive letters, called drive designators, to resources. If it is a local designator (drive C: for example) the request is passed on to the local bus. If it is a network designator the request is forwarded to the server, which opens the file or transfers the print job to the network printer, etc. This makes the application program believe that it is simply working with a very large hard drive or with a local printer. It does not need to know anything about networks.

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Network + Training & Test Preparation Guide

NOS Packages There are a multitude of network operating systems available for use. Each of them has its own advantages and disadvantages. In this section, we will take a closer look a some of the more popular ones. Novell NetWare The NetWare operating system has been around for a long time. In the past, it was the most popular server operating system, but it is losing market share to Microsoft servers every year. It is a reliable operating system that provides performance and security. The earliest version (2.2) was designed to operate on 286 machines. Versions 3.12 and 4.11 operate on 386, 486, or Pentium machines. Version 4.11 is called IntranetWare. It is Novell’s push to gain market share and is a way of creating an Intranet, which is like the Internet but within a network or company. Version 6.5 is now on the market. NetWare is based upon the industry standard X500 directory architecture. NetWare is administered through NetADMIN, which is a DOS-based utility, or through NWADMIN.EXE, which is a Windows-based utility. It may be installed in either the client or server format. •

NetWare’s popularity is due largely to its ability to provide services across multioperating system environments.

NetWare Directory Services (NDS) NDS (NetWare Directory Services) is the core of the NetWare operating system. It is a hierarchically organized database that provides security, name service, messaging, routing, web-publishing, management, and file and print services. Organization of network resources such as users, groups, servers, and volumes is also handled with NDS. With NDS’ single point logon, a user may logon from anywhere on the network and gain access with all of their assigned rights and privileges intact. NetWare File Services The NetWare file server hard drive may be mapped to a client and the client machine will recognize the drive as a logical drive and be able to access it as it would any other drive in the computer. NetWare Security The purpose of a network may be to share resources, but there will always be data in any network to which access must be restricted. NetWare provides more than adequate network security by using a combination of approaches. First, login security provides authentication and verification of user name, password, time, and account restrictions. Trustee rights regulate which directories and files a user can access, as well as what kind of access they have. Directory and file attributes are used to set the types of access for a file or directory such as viewed, copied, shared, non-shareable, deleted, or changed. See Chapter 10 for more information on network security.

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Chapter 2 – Network Operating Systems (NOS) NetWare Print Services NetWare Print Services can support up to 256 printers. The file server and the print server can be the same computer. Print requests are first routed to the file server, next to the print server, and finally to the printer. Printers may be attached to the server, a workstation, or directly to the network. NetWare Message Handling Service (MHS) MHS may be installed on any server and configured to be a network wide E-mail system. It is compatible with E-mail programs such as Novell’s GroupWise and Microsoft Mail, as well as others. NetWare also provides a method of using simple commands to send messages to other users on the network. You can send messages to individuals or to groups very easily. You can even send messages to everyone in a group, except an individual workstation. NetWare Minimum Requirements The following are the minimum installation requirements as specified by Novell for installing their server software:

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Network + Training & Test Preparation Guide

Version 2.X: CPU

286 or higher

RAM

2.5 MB

Free Hard Drive Space

20 MB

Version 3.X: CPU

386 or higher

RAM

6 MB

Free Hard Drive Space

30 MB

Version 4.X: CPU

386 or higher

RAM

16 MB

Free Hard Drive Space

105 MB

Version 5: CPU

Pentium Class or higher

RAM

64 MB

Free Hard Drive Space

550 MB

Client Software The client software may be installed on any computer running any of the following:

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•

DOS 3.1 or later and the NetWare Client32 for DOS

•

MS Windows 3.0 or later and the NetWare Client32 for DOS

•

OS/2 1.1 or later (Standard or Extended Edition) and the NetWare Client32 for OS/2

•

OS/2 2.11 or OS/2 Warp and the NetWare Client32 for OS/2

•

Macintosh 6.0 or later and the NetWare Client32 for Macintosh OS

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Chapter 2 – Network Operating Systems (NOS) NetWare Interoperability As the word implies, interoperability simply means the ability of an operating system to operate with other systems. As we’ve already discussed, NetWare is extremely efficient at operating with other systems. The NetWare client can be installed with almost any other operating system. Problems do occur when trying to operate within the Windows NT domain, but Windows NT contains services such as NWLink and Gateway Service for NetWare (GSNW) that allow them to work together effectively. Microsoft Windows NT Network Operating System While NetWare was the network operating system of the 80s and early 90s, its popularity is being replaced by Microsoft Windows Servers. Unlike NetWare, Windows combines the operating system and the network operating system into one. This makes it more difficult to work in multi-operating system environments, but it does have several advantages. The services provided by the server are more powerful and it is easier for programmers to develop software that takes advantage of Microsoft’s server/workstation technology. The NT Kernel, which as at the base of all Microsoft’s servers, actually evolved from a project that was jointly developed by IBM and Microsoft (OS/2). Microsoft released the Windows NT operating system and a network operating system version, Windows NT Advanced Server in 1993. Today, Windows NT has two versions: Server (the server software) and Workstation (the client software). Although Server and Workstation can both operate as either stand-alone or network systems, Server is much more powerful so that it may provide network management. The newest of these server operating systems, Windows 2000 Server and Windows Server 2003, offer even more advantages and stronger security than their predecessors. Windows File Services Like NetWare, the Windows servers may be configured to store each workstation’s directories in order to provide centralized data management and backups. Files in Windows may be shared by using a simple file sharing method similar to sharing files on a peer-to-peer network. This type is performed by each workstation or server publicly sharing a directory on the network. The attributes such as Read, Change, Full Control, or No Access may be set on the directory. You must have administrative privileges in order to share anything on a Windows network. In order to take maximum advantage of the security features in Windows , another security method must be utilized. With this method, you may assign directory and filelevel permissions to the data, allowing restricted access to individuals or groups. The NT file system (NTFS) must be utilized in order to take full advantage of Windows security features. The advanced security features of Windows are not available if you choose the DOS file system (FAT - File Allocation Table) during installation. It is possible to use both the NTFS and FAT file systems as long as they are in different partitions on the hard drive. A disadvantage of this is that anyone not using NTFS cannot recognize NTFS directories, and is limited to the publicly shared files mentioned earlier.

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Network + Training & Test Preparation Guide Windows Server Security Security was a major concern in the development of Windows Servers, especially with the latest Windows Server 2003 family. Microsoft uses domains to control access and authenticate users and computers. A domain is simply a group of users, computers, and resources with a shared security database. At least one domain controller is assigned to each domain. A domain controller is a server that maintains and manages all accounts, permissions, and user rights. Rights must be assigned to users in order for them to use any resources or perform any tasks in the domain.. See Chapter 10 for more information on network security. Windows Print Servers Any workstation or server may perform as a print server in a Windows network. A printer need only be shared to the network to be accessible to anyone on the network. (Of course a user still has to be assigned the permission to access a resource.) Installing a network printer is just like installing a local printer, except that you are asked if it is to be a network or local printer. Even if you are installing a local printer, you are given the option to share it to the network. Remember, more than one printer can be installed to any machine. Printing is as easy as selecting the printer that you want to use (assuming that you have the appropriate permissions). Windows Network Services There are many services available in Windows to manage network flow: Messenger Service monitors the network and provides pop-up messages for the user. Alerter Service sends the notifications that are monitored by the messenger service. Browser Service provides a list of all available domain and workgroup servers. Workstation Service is the redirector service.. Server Service provides access to network resources.

Interoperability As Novell NetWare was the “big kid on the block” when NT came on the scene, Microsoft wanted to make NT as compatible with NetWare as possible. This trend continued with the latest Windows server operating systems (Windows 2000 Server and Windows Server 2003. The following is a list of services included with Windows Server software to ensure NetWare compatibility: NWLink is actually a clone of Novell’s IPX/SPX protocol and is used for communication between Microsoft and NetWare.

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Chapter 2 – Network Operating Systems (NOS) GSNW (Gateway Services for NetWare) provides the gateway between an Microsoft domain and the NetWare server. This is necessary because all Microsoft client workstations in a domain must connect to a NetWare server through a single contact point. Network performance will decrease as the number of computers accessing the gateway increases. Installing GSNW automatically installs the NWLink protocol as well. CSNW (Client Services for NetWare) is the Microsoft service that allows workstations to use file and print services on a NetWare server. It can be installed on the Microsoft client to allow it to connect the Netware server directly. Installing CSNW automatically installs the NWLink protocol as well. FPNW (File and Print Service for NetWare) is a utility that enables NetWare clients to access Microsoft file and print services. This software is not included with Netware but can be purchased separately. DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems. It allows Novell NDS computers to be managed just as Microsoft domain controllers. Migration Tool for NetWare is a tool used to convert from NetWare to Windows. Its purpose is to move (called migrating) NetWare account information to Microsoft’s domain controller. Windows 2000 Server Windows 2000 server is the server-side OS to Windows 2000 Professional. Probably the biggest feature in Windows 2000 server is the addition of Active Directory. Active Directory is a directory service that stores information about objects on a network and makes this information available to both users and administrators. It allows for a single logon to access resources anywhere on the network. It also offers an improved version of NTFS and fault tolerant versions of RAID on dynamic drives. Group policies can be utilized with server 2000, which govern what users can see and do on the network. Windows Server 2003 Windows Server 2003 is the latest in the line of Microsoft server operating systems. It provides all of the advantages of Windows 2000 Server, but it adds many features that are designed exclusively for security. Windows Server 2003 offers a more secure Web Server (IIS 6.0) than the previous version in Windows 2000 (IIS 5.0). In addition, it has more “locked down” security templates that make it less likely that users will try to go around the security. In fact, Windows Server 2003 is the first Windows server that was built primarily with security in mind. Previous Microsoft server operating systems were built to serve and then had security features to protect them. In contrast, when using Windows Server 2003 you typically must remove or configure security boundaries in order to get the server to...well serve. UNIX Operating Systems UNIX stands for UNiplexed Information and Computing System. Even though UNIX was not designed as a network operating system it can be, and is, used as such. UNIX is a Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide bulky operating system. It is primarily used on minicomputers and has many features that are favored in the engineering and scientific environments. UNIX is a multi-tasking, multi-user, general-purpose operating system. A UNIX system consists of a host (a central computer) with terminals for the users. These terminals are not stand-alone computers, but rely solely on the UNIX host for resources. Software is available, however, to convert the UNIX host into a file server. The multi-tasking UNIX host will run this software as just another application. The UNIX-based workstation can run DOS, OS/2, UNIX, or Macintosh System 7 for its operating system. A file redirector is used to allow the workstation to store and retrieve UNIX files as if they were in the original format. Banyan VINES (Virtual Integrated Network Service) Like Windows, Banyan VINES is a client/server-based network operating system. At one time, it was an extremely popular network operating system, but has lost market share since the arrival of NetWare. VINES was originally based on UNIX and has a directory services application called StreetTalk layered on top. StreetTalk provides directory, security, and messaging services, as well as file and printer sharing. Like Novell NetWare, VINES is a great performer in multi-operating system environments. Linux is another operating system similar to UNIX. It is a publicly open system that has made it popular among enthusiasts already familiar with a UNIX interface. At its inception, Linux was designed to be less expensive than UNIX; in fact the software is available for a free download. It uses a GUI (graphical user interface), TCP/IP, and many other features associated with an OS. It is available on both Intel (PC) and PowerPC (Mac) platforms, as well as others. Linux is open source, which means that it can be changed by a software programmer. Because of its open source nature, many variations of Linux have been created over the years such as Caldera and Red Hat.

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Chapter 2 – Network Operating Systems (NOS) The Macintosh ("Mac") was developed by Apple Computer in 1984. In conjunction with Xerox, they developed what later became known as the mouse and the first GUI display. The Mac OS X is the most current operating system used in conjunction with the Apple computer (at the time of the writing of this book), and the processor used in Apples today is called PowerPC. Macs are known for being used primarily in video or graphic production, but users also use them personally, both at home and on the go.

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Peer-to-Peer Networking In a peer-to-peer network there are no separate computers that act as servers. All of the computers on the network can act as either clients or servers depending upon the needs of the user. This type of network is most often used when fewer than ten computers are involved. A peer-to-peer network is simple and inexpensive to install. The computers are simply cabled together, and as long as each computer has an operating system capable of client/sharing (e.g. Windows 95 and up) they will be able to communicate via the network. In a peer-to-peer network all computers are equal. A disadvantage of the peer-to-peer network is that since users are responsible for their own systems’ security, network security is unreliable. Also, a peer-to-peer network is difficult to expand.

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Chapter 1 – Networking Fundamentals

Basic Network Structure (Topology) A network’s basic structure, or topology, refers to its physical layout, design, map, scheme, or diagram. As a network professional, you will need to know how to choose the network topology that will best suit the needs of your network. The type and capabilities of the equipment that will be used, future growth needs, and how a network will be managed are all potential problems that need to be considered when planning a network. Setting up a network requires more than just cabling the computers together. Different topologies have different cabling requirements. NICs, (Network Interface Cards, also called Network Adapter Cards), connectors, how the computers will talk to each other (protocols), and even how the cabling is run through a building, are all determined by the topology used. There are three standard topologies that a network professional needs to understand: •

Bus Topology

•

Star Topology

•

Ring Topology

Bus Topology The simplest and probably the most used form of network topologies is the Bus topology (sometimes called a linear bus). The nodes (computers or devices connected to the network) are all connected along a single cable. This cable is called a trunk, backbone, or segment. Devices on a Bus topology communicate by sending data to a specific address on the network (a device’s address). An electronic signal is sent out on the cable to all of the devices connected on the network. However, only the device whose address matches the address encoded in the signal will respond to the signal. Only one computer at a time can transmit data on a Bus network or signals will collide and the transmission will fail. This means that the more computers that are connected to a Bus the slower the network becomes as devices are waiting to transmit or retransmit. The Bus topology is a passive topology. Devices only listen for data being transmitted, they do not move the transmissions along. The signal is sent out on the cable and it travels from one end of the cable to the other. If not prevented, the signal would travel back and forth along the cable and cause what is known as signal bounce. While the signal is bouncing back and forth, it prevents other devices from sending data. To stop signal bounce, a component called a terminator is installed at each end of the cable. A terminator absorbs the signal and stops signal bounce. In a Bus network, if the cable breaks, the network will go down and devices will not be able to communicate with each other.

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Network + Training & Test Preparation Guide

Star Topology In a Star topology, all devices are connected to a central point called a hub. It requires a lot more cable than the Bus topology, but the advantage is that if one computer (or the cable that connects one computer to the hub) goes down, the rest of the network will still continue to function. If the hub fails, however, the entire network will go down.

Ring Topology In a Ring topology, the devices are connected in one continuous circle of cable. There are no ends to terminate. The data is transmitted around the loop in one direction and passes through each computer on the network. The Ring is not a passive topology like the Bus topology. The signal is actually boosted and sent on along the cable when it passes through the computers on the network. A disadvantage is that if one computer fails, it can affect the entire network.

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Chapter 1 – Networking Fundamentals

With IBM Token Ring networks, the ring is actually in a special type of hub called a Multistation Access Unit (MSAU). In these networks, a computer can fail and not prevent the network from functioning. Special Topologies In addition to the above topologies, today’s networking professional will encounter many network topologies that are combinations of the above configurations. These are known as Hybrid topologies. Before you can understand some of these special topologies, you will need to know the difference between a physical and a logical topology. So far, we have been discussing physical topologies. These are the methods in which a network is actually wired. You will be able to see a physical topology. A logical topology, on the other hand, is how the network actually works. For example, some Ethernet networks today are wired using a using multiple hubs. This gives us a physical star topology. However, they operate between the hubs like a bus topology and are therefore a logical bus. Also, Token Ring networks are physical stars and logical rings. Hybrid Topologies The Star Bus topology is a hybrid of the Star and Bus topologies. It consists of several Star topology networks that are linked using linear Bus trunks. The Star Ring topology is similar to the Star Bus, but the hubs in a Star Ring are connected in a star pattern by a main hub. Mesh Topology In the Mesh topology every device is connected to every other device by separate cables and has redundant paths. This is very expensive to install but it is extremely reliable because of the redundant paths.

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Network + Training & Test Preparation Guide

Wireless Topology A Wireless topology is one in which there aren’t any cables connecting the network devices to the LAN or one which the LAN uses wireless technology between access points. Since each computer has its own connection to the wireless access point (WAP), the topology of a wireless network is that of an “invisible star”. . The benefits of wireless technology will be discussed at length in Chapter 4 of this book.

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Chapter 1 – Networking Fundamentals

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Network + Training & Test Preparation Guide

Network Access The topologies that we have been discussing describe the way in which the computers and other devices on a network are connected. This is based on the media or wiring of the network. Another aspect of networks that is related to topology is the way in which the network is accessed by individual devices. With several devices connected to one media, we create kind of a “party line”. The method that is used for an individual device to be able to use the network party line is called media access. The two most common network standards are distinguished by their respective media access methods, they are called Token Ring and Ethernet. We will also cover access methods in more detail in the chapter “Network Protocols and Standards.” Token Passing Token passing is the method of sending data around a Token Ring topology. A token is passed along from device to device until it is received by a computer that needs to transmit. The sending computer grabs the token and encodes it with addressing information for the receiving computer and sends it out on the ring. It is passed along from device to device until it arrives at the computer whose addressing information matches the one encoded on the token, and the message is delivered. The receiving computer then sends the token back to the sending computer to let it know that it received the message. The sending machine then creates a new token to send around the ring that will be grabbed by the next device that wants to transmit data on the network. Since there is only one token, only one device at a time can communicate on the network.

Ethernet Ethernet uses a system known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). Carrier Sense means the network card listens to the cable for a quiet period during which it can send messages. Multiple Access means that more than one computer 26

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Chapter 1 – Networking Fundamentals can be connected to the same cable. Collision Detection is the ability to detect whether messages have collided in transit (neither message will arrive at their destination and both will be retransmitted).

Collision Detection Fast Ethernet Fast Ethernet was developed to meet the increasing demands on networks. Fast Ethernet works on the same principals as Ethernet but operates at 10 times the speed of the original. Ethernet transmits at 10 Mbps and Fast Ethernet transmits at 100 Mbps.

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Network + Training & Test Preparation Guide

Hubs and Concentrators More and more networks are using hubs and they are pretty much standard equipment in today’s networks. Today, hubs come in a variety of names depending on their function. The most common name used with Ethernet is a hub or a concentrator. With a Token Ring, they are called MSAUs (Multiple Station Access Units). Essentially, they are all the same, since they provide a common location for connecting the cabling of a network. Just remember, not all hubs are the same and you must use one that is designed to meet the needs of the network. Hubs can be classified as either passive or active. Passive Hubs A passive hub acts as a connection point only. Signals pass through the hub but are not regenerated or amplified. Passive hubs do not require any electrical power to function.

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Chapter 1 – Networking Fundamentals Active Hubs Most of the hubs used today are active hubs. An active hub regenerates or amplifies a signal when it is passed through. This type type of hub requires electrical power to function.

Hub-Based Networks Hub-based networks are increasing in popularity. They have many advantages over other types of networks: 1) If a cable breaks only the portion of the network on that segment is affected. 2) Centralized monitoring of traffic and activity along with diagnostic capabilities are available. 3) A variety of cable types can be accommodated. 4) Expanding the network can be easily accomplished by using hubs.

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Network + Training & Test Preparation Guide

Summary In this chapter we learned that the main reason for networking (as it relates to computers) is the sharing of resources. The two types of networks are LANs and WANs. A LAN is the smallest form and is the basic building block for larger networks. A WAN is not geographically limited and typically has greater speed of communication than a WAN, and the Internet is the world’s largest WAN. We also learned about the two basic network classifications of networks: the peer-to-peer network and the server-based network. It is important to know the differences between these two classifications and the advantages and disadvantages of each. Topology is a term we use to describe the logical shape of the connection of computers in a network. The three main types of topology are bus, star, and ring. Be sure to complete the following exercises and review questions. If you are having trouble with any of these concepts, go back and review the chapter again.

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Chapter 1 – Networking Fundamentals

KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword

Definition

Active Hub Application Application Server Bus Topology Client Data Fax Server File Server Hub Hybrid Topology LAN Mail Server MAN Media Mesh Topology Network Network Administrator Passive Hub Peer-to-peer Peripheral Print Server Specialized Solutions, Inc.

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Keyword Resources Ring Topology Security Server Server-based Sharing Star Topology Token Passing User WAN Wireless Topology

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Definition

Chapter 1 – Networking Fundamentals

Review Questions - Chapter 1 1. What are the key differences between a local area network (LAN) and a wide area network (WAN)?

2. What is the main reason for networking computers?

3. What is a “sneaker net”?

4. Name some advantages of having centralized documents.

5. What does MAN stand for and why is it no longer in use?

6. Name some advantages of a Peer-to-Peer network.

7. Name some disadvantages of a Peer-to-Peer network.

8. Name some advantages of a Server-based network.

9. Name some disadvantages of a Server-based network.

10. Name the three basic topologies.

11. What is the difference between a physical and logical topology?

12. Name two media access methods.

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Chapter 2 – Network Operating Systems (NOS)

Chapter 2 - Network Operating Systems (NOS) Up to this point we have focused on the design aspects of networking. Even if you have the best network design composed of the best hardware in the universe, if you don’t have the software to run it, it is just a pile of metal and plastic. You can get it all set up and turn on the power, but without an operating system, it will just sit there. This chapter is all about the various operating systems with which a networking professional needs to be familiar. When we are talking about operating systems, what we are really talking about are network operating systems. Network operating systems (NOS) are specialized operating systems designed to integrate computers in a networking environment. Most of today’s client and server operating systems have a built-in network operating system. When we refer to the operating system in this chapter, we are referencing the built-in network operating system component. In this chapter we will explore the features and benefits of the more popular network operating systems. We will also discuss their minimum requirements and interoperability capabilities. The differences between server and client operating systems as well as preemptive and non-preemptive multitasking will be covered as well.

What is an Operating System? Not that long ago, network operating systems were designed to operate on top of an existing operating system. A computer needed two sets of software in order to function in a networking environment. Today, most networked computers run software that was specifically designed to run both the computer’s stand-alone functions as well as its networking functions. Hardware resources such as RAM, processor time, hard disk space, and peripherals are all controlled by the operating system (the software). The operating system is also responsible for the running of applications (e.g. word-processing, spreadsheet, and database programs). The main objective is to make sure that the hardware and the applications are all compatible with each other, as well as the operating system.

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Network + Training & Test Preparation Guide Preemptive vs. Non-preemptive Multitasking Multitasking, put simply, means that an operating system has the ability to perform more than one task at a time. A true multitasking (multi-processing) operating system is able to process as many tasks as it has processors. Most operating systems appear to be performing multiple tasks by alternating between tasks until they are all completed. Preemptive multitasking means that the operating system can take control of the processor without a task’s permission. Non-preemptive multitasking is when the task decides when it is done with the processor. In non-preemptive multitasking, the processor is never taken away from a task. Preemptive multitasking began with Windows 95 and the Intel Pentium processor. It is used on all of the latest operating systems.

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Chapter 2 – Network Operating Systems (NOS)

What is a Network Operating System (NOS)? A NOS is an operating system that includes other software, such as BSD UNIX, Novell NetWare, Microsoft Client, or a similar program, to communicate with other computers over a network. Peer-to-Peer LANs Many smaller networking environments utilize the peer-to-peer network configuration. Peer-to-peer LANs are an excellent choice for the network that has less than ten computers and no need of security (such as a small office environment). It is certainly the most economical of the networking choices. Usually only NICs and cabling will need to be purchased to implement this kind of network. A peer-to-peer LAN is not a client/server-based network. Instead, each workstation may act as either a client or a server depending upon whether it is accessing resources on another workstation or if another workstation is accessing its resources. Usually this type of network only shares files and peripheral devices. Most of the operating systems in use today are already capable of managing this type of network. Windows 95/98 Windows 95 and Windows 98 are operating systems that include a network operating system. Their new graphical interface and networking capabilities make them a vast improvement over their predecessors. They use an icon called the Network Neighborhood for desktop access of the network. All shared resources are arranged on a hierarchical basis and displayed in Network Neighborhood. Plug-n-Play technology has also made installing a NIC much easier. Windows 95/98 is also able to better identify NICs. To install a NIC with Windows 95/98 is as simple as installing the card, turning on the computer and answering questions. Then, all you have to do is share any directories and peripherals to the network, and you have a working network. Windows 95/98 also performs very well as a client with both the NetWare and Windows NT operating systems. It is necessary to install the requester software (NetWare Client32 for Windows 95) with NetWare. With NT the only drawback is that you will not be able to utilize NT’s advanced security features because Windows 95 is not compatible with the NTFS file system. Windows ME Windows ME is the client operating system that has followed the Windows 9x operating systems. It is well-suited for editing home movies, moving photos to the Web, and archiving music. It protects critical files and will allow you to revert your system back to normal if anything goes wrong. Help and support is improved from Windows 98 and home networking is made easier than ever.

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Network + Training & Test Preparation Guide Windows 2000 Professional Windows 2000 Professional is the client counterpart to Windows 2000 server. It features file protection, driver certification, remote OS installation, multilingual support, peer-topeer support for Windows 9x and NT, EFS (Encrypting File System), IPsec and Kerberos support. It also supports Microsoft Management Console (MMC) and group policies. Windows XP Home Windows XP Home edition is the newest edition of Microsoft’s OS for home users. It allows for faster user switching, a simplified visual design, It also uses System Restore, like ME, which allows for safety when installing additional software or making changes to the computer’s configuration. It, like the rest of the client OS software mentioned here, is equipped to be networked easily. Other Peer-to-Peer LANs The following table lists other peer-to-peer LAN software and their manufacturers that the networking professional may come across in real life but are unlikely to be on the test:

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Chapter 2 – Network Operating Systems (NOS)

Software Name

Manufacturer

10NetPlus

Digital Communications Associates, Inc.

AppleTalk

Apple Computer

Easy Net

LanMark

GV LAN OS

Grapevine LAN Products

LANsmark

D-Link Systems

LANsoft

ACCTon Technology

LANStep

Hayes Microcomputer Products

LANtastic

Artisoft

NET/30

Invisible Software

Network OSCBIS

Peachtree

OS/2 Warp

IBM Corporation

Personal NetWare

Novell

POWERLan

Performance Technology

ReadyLink

Compex

WEB

WebCorp

Server/Client Software In a peer-to-peer network, the computers act as both a client and a server. However, it is necessary to have an operating system that can perform in this environment. In a Serverbased network, the purpose of a network operating system is to connect all devices on a network (computers and peripherals) and to coordinate their usability. This can also provide accessibility and security for all devices on a network. Some network operating systems require that different versions are installed depending on whether a computer is the server (provides resources remotely over a network) or a client (uses resources locally).

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Network + Training & Test Preparation Guide There are two types of networking software that must be considered: •

Client Software

•

Server Software

Client Software If you type a command for your stand-alone computer to perform a task, the command is processed over the computer’s internal CPU via the computer’s local bus. However, if you were requesting resources or services that exist on a remote server, the operating system has to have the capability to redirect (forward) the request away from the local bus, out onto the network, and to the server. The component that handles these requests is called the redirector. Server Software As their name implies, Servers exist to serve. They process requests from clients for resources such as files and peripherals. They are the storage facility for the bulk of the data in a network environment and as such are an excellent point from which to centrally manage a network. Unlike most client software, server software includes services for the following: •

Managing User Accounts

•

Security

•

Data Protection

Managing User Accounts Servers make it possible to manage users from a central location. Users are required to enter a password before they can log on and gain access. Administrators set up and manage user accounts and passwords. Security Administrators can set up the accounts to determine who gets privileges to what resources and change them as needed (including denying access). The server keeps track of who is logged onto a network and what resources have been (or are being) accessed. Network security is discussed in greater detail in Chapter 10. Data Protection As we already discussed, most of the data is stored on the server. This makes it an excellent point from which to perform regular backups. Most network administrators provide some sort of fault-tolerance system on the server. At the very least, the server should be attached to an uninterruptible power supply (UPS). Some networks even cluster server so that more that one server can share a database of information. This 40

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Chapter 2 – Network Operating Systems (NOS) provides for load balancing of the server resources as well as fault tolerance if one server were to fail. The Redirector (Requester) The redirector (in Novell NetWare this is called the requester) is responsible for forwarding requests away from the local bus and redirecting them to the server. Basically, it is a section of code located in the network operating system that intercepts requests and determines if they are local requests, or if they need to be redirected to the server. The purpose of the redirector is to make network resources look like local resources to application programs. It does this by assigning drive letters, called drive designators, to resources. If it is a local designator (drive C: for example) the request is passed on to the local bus. If it is a network designator the request is forwarded to the server, which opens the file or transfers the print job to the network printer, etc. This makes the application program believe that it is simply working with a very large hard drive or with a local printer. It does not need to know anything about networks.

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Network + Training & Test Preparation Guide

NOS Packages There are a multitude of network operating systems available for use. Each of them has its own advantages and disadvantages. In this section, we will take a closer look a some of the more popular ones. Novell NetWare The NetWare operating system has been around for a long time. In the past, it was the most popular server operating system, but it is losing market share to Microsoft servers every year. It is a reliable operating system that provides performance and security. The earliest version (2.2) was designed to operate on 286 machines. Versions 3.12 and 4.11 operate on 386, 486, or Pentium machines. Version 4.11 is called IntranetWare. It is Novell’s push to gain market share and is a way of creating an Intranet, which is like the Internet but within a network or company. Version 6.5 is now on the market. NetWare is based upon the industry standard X500 directory architecture. NetWare is administered through NetADMIN, which is a DOS-based utility, or through NWADMIN.EXE, which is a Windows-based utility. It may be installed in either the client or server format. •

NetWare’s popularity is due largely to its ability to provide services across multioperating system environments.

NetWare Directory Services (NDS) NDS (NetWare Directory Services) is the core of the NetWare operating system. It is a hierarchically organized database that provides security, name service, messaging, routing, web-publishing, management, and file and print services. Organization of network resources such as users, groups, servers, and volumes is also handled with NDS. With NDS’ single point logon, a user may logon from anywhere on the network and gain access with all of their assigned rights and privileges intact. NetWare File Services The NetWare file server hard drive may be mapped to a client and the client machine will recognize the drive as a logical drive and be able to access it as it would any other drive in the computer. NetWare Security The purpose of a network may be to share resources, but there will always be data in any network to which access must be restricted. NetWare provides more than adequate network security by using a combination of approaches. First, login security provides authentication and verification of user name, password, time, and account restrictions. Trustee rights regulate which directories and files a user can access, as well as what kind of access they have. Directory and file attributes are used to set the types of access for a file or directory such as viewed, copied, shared, non-shareable, deleted, or changed. See Chapter 10 for more information on network security.

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Chapter 2 – Network Operating Systems (NOS) NetWare Print Services NetWare Print Services can support up to 256 printers. The file server and the print server can be the same computer. Print requests are first routed to the file server, next to the print server, and finally to the printer. Printers may be attached to the server, a workstation, or directly to the network. NetWare Message Handling Service (MHS) MHS may be installed on any server and configured to be a network wide E-mail system. It is compatible with E-mail programs such as Novell’s GroupWise and Microsoft Mail, as well as others. NetWare also provides a method of using simple commands to send messages to other users on the network. You can send messages to individuals or to groups very easily. You can even send messages to everyone in a group, except an individual workstation. NetWare Minimum Requirements The following are the minimum installation requirements as specified by Novell for installing their server software:

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Version 2.X: CPU

286 or higher

RAM

2.5 MB

Free Hard Drive Space

20 MB

Version 3.X: CPU

386 or higher

RAM

6 MB

Free Hard Drive Space

30 MB

Version 4.X: CPU

386 or higher

RAM

16 MB

Free Hard Drive Space

105 MB

Version 5: CPU

Pentium Class or higher

RAM

64 MB

Free Hard Drive Space

550 MB

Client Software The client software may be installed on any computer running any of the following:

44

•

DOS 3.1 or later and the NetWare Client32 for DOS

•

MS Windows 3.0 or later and the NetWare Client32 for DOS

•

OS/2 1.1 or later (Standard or Extended Edition) and the NetWare Client32 for OS/2

•

OS/2 2.11 or OS/2 Warp and the NetWare Client32 for OS/2

•

Macintosh 6.0 or later and the NetWare Client32 for Macintosh OS

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Chapter 2 – Network Operating Systems (NOS) NetWare Interoperability As the word implies, interoperability simply means the ability of an operating system to operate with other systems. As we’ve already discussed, NetWare is extremely efficient at operating with other systems. The NetWare client can be installed with almost any other operating system. Problems do occur when trying to operate within the Windows NT domain, but Windows NT contains services such as NWLink and Gateway Service for NetWare (GSNW) that allow them to work together effectively. Microsoft Windows NT Network Operating System While NetWare was the network operating system of the 80s and early 90s, its popularity is being replaced by Microsoft Windows Servers. Unlike NetWare, Windows combines the operating system and the network operating system into one. This makes it more difficult to work in multi-operating system environments, but it does have several advantages. The services provided by the server are more powerful and it is easier for programmers to develop software that takes advantage of Microsoft’s server/workstation technology. The NT Kernel, which as at the base of all Microsoft’s servers, actually evolved from a project that was jointly developed by IBM and Microsoft (OS/2). Microsoft released the Windows NT operating system and a network operating system version, Windows NT Advanced Server in 1993. Today, Windows NT has two versions: Server (the server software) and Workstation (the client software). Although Server and Workstation can both operate as either stand-alone or network systems, Server is much more powerful so that it may provide network management. The newest of these server operating systems, Windows 2000 Server and Windows Server 2003, offer even more advantages and stronger security than their predecessors. Windows File Services Like NetWare, the Windows servers may be configured to store each workstation’s directories in order to provide centralized data management and backups. Files in Windows may be shared by using a simple file sharing method similar to sharing files on a peer-to-peer network. This type is performed by each workstation or server publicly sharing a directory on the network. The attributes such as Read, Change, Full Control, or No Access may be set on the directory. You must have administrative privileges in order to share anything on a Windows network. In order to take maximum advantage of the security features in Windows , another security method must be utilized. With this method, you may assign directory and filelevel permissions to the data, allowing restricted access to individuals or groups. The NT file system (NTFS) must be utilized in order to take full advantage of Windows security features. The advanced security features of Windows are not available if you choose the DOS file system (FAT - File Allocation Table) during installation. It is possible to use both the NTFS and FAT file systems as long as they are in different partitions on the hard drive. A disadvantage of this is that anyone not using NTFS cannot recognize NTFS directories, and is limited to the publicly shared files mentioned earlier.

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Network + Training & Test Preparation Guide Windows Server Security Security was a major concern in the development of Windows Servers, especially with the latest Windows Server 2003 family. Microsoft uses domains to control access and authenticate users and computers. A domain is simply a group of users, computers, and resources with a shared security database. At least one domain controller is assigned to each domain. A domain controller is a server that maintains and manages all accounts, permissions, and user rights. Rights must be assigned to users in order for them to use any resources or perform any tasks in the domain.. See Chapter 10 for more information on network security. Windows Print Servers Any workstation or server may perform as a print server in a Windows network. A printer need only be shared to the network to be accessible to anyone on the network. (Of course a user still has to be assigned the permission to access a resource.) Installing a network printer is just like installing a local printer, except that you are asked if it is to be a network or local printer. Even if you are installing a local printer, you are given the option to share it to the network. Remember, more than one printer can be installed to any machine. Printing is as easy as selecting the printer that you want to use (assuming that you have the appropriate permissions). Windows Network Services There are many services available in Windows to manage network flow: Messenger Service monitors the network and provides pop-up messages for the user. Alerter Service sends the notifications that are monitored by the messenger service. Browser Service provides a list of all available domain and workgroup servers. Workstation Service is the redirector service.. Server Service provides access to network resources.

Interoperability As Novell NetWare was the “big kid on the block” when NT came on the scene, Microsoft wanted to make NT as compatible with NetWare as possible. This trend continued with the latest Windows server operating systems (Windows 2000 Server and Windows Server 2003. The following is a list of services included with Windows Server software to ensure NetWare compatibility: NWLink is actually a clone of Novell’s IPX/SPX protocol and is used for communication between Microsoft and NetWare.

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Chapter 2 – Network Operating Systems (NOS) GSNW (Gateway Services for NetWare) provides the gateway between an Microsoft domain and the NetWare server. This is necessary because all Microsoft client workstations in a domain must connect to a NetWare server through a single contact point. Network performance will decrease as the number of computers accessing the gateway increases. Installing GSNW automatically installs the NWLink protocol as well. CSNW (Client Services for NetWare) is the Microsoft service that allows workstations to use file and print services on a NetWare server. It can be installed on the Microsoft client to allow it to connect the Netware server directly. Installing CSNW automatically installs the NWLink protocol as well. FPNW (File and Print Service for NetWare) is a utility that enables NetWare clients to access Microsoft file and print services. This software is not included with Netware but can be purchased separately. DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems. It allows Novell NDS computers to be managed just as Microsoft domain controllers. Migration Tool for NetWare is a tool used to convert from NetWare to Windows. Its purpose is to move (called migrating) NetWare account information to Microsoft’s domain controller. Windows 2000 Server Windows 2000 server is the server-side OS to Windows 2000 Professional. Probably the biggest feature in Windows 2000 server is the addition of Active Directory. Active Directory is a directory service that stores information about objects on a network and makes this information available to both users and administrators. It allows for a single logon to access resources anywhere on the network. It also offers an improved version of NTFS and fault tolerant versions of RAID on dynamic drives. Group policies can be utilized with server 2000, which govern what users can see and do on the network. Windows Server 2003 Windows Server 2003 is the latest in the line of Microsoft server operating systems. It provides all of the advantages of Windows 2000 Server, but it adds many features that are designed exclusively for security. Windows Server 2003 offers a more secure Web Server (IIS 6.0) than the previous version in Windows 2000 (IIS 5.0). In addition, it has more “locked down” security templates that make it less likely that users will try to go around the security. In fact, Windows Server 2003 is the first Windows server that was built primarily with security in mind. Previous Microsoft server operating systems were built to serve and then had security features to protect them. In contrast, when using Windows Server 2003 you typically must remove or configure security boundaries in order to get the server to...well serve. UNIX Operating Systems UNIX stands for UNiplexed Information and Computing System. Even though UNIX was not designed as a network operating system it can be, and is, used as such. UNIX is a Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide bulky operating system. It is primarily used on minicomputers and has many features that are favored in the engineering and scientific environments. UNIX is a multi-tasking, multi-user, general-purpose operating system. A UNIX system consists of a host (a central computer) with terminals for the users. These terminals are not stand-alone computers, but rely solely on the UNIX host for resources. Software is available, however, to convert the UNIX host into a file server. The multi-tasking UNIX host will run this software as just another application. The UNIX-based workstation can run DOS, OS/2, UNIX, or Macintosh System 7 for its operating system. A file redirector is used to allow the workstation to store and retrieve UNIX files as if they were in the original format. Banyan VINES (Virtual Integrated Network Service) Like Windows, Banyan VINES is a client/server-based network operating system. At one time, it was an extremely popular network operating system, but has lost market share since the arrival of NetWare. VINES was originally based on UNIX and has a directory services application called StreetTalk layered on top. StreetTalk provides directory, security, and messaging services, as well as file and printer sharing. Like Novell NetWare, VINES is a great performer in multi-operating system environments. Linux is another operating system similar to UNIX. It is a publicly open system that has made it popular among enthusiasts already familiar with a UNIX interface. At its inception, Linux was designed to be less expensive than UNIX; in fact the software is available for a free download. It uses a GUI (graphical user interface), TCP/IP, and many other features associated with an OS. It is available on both Intel (PC) and PowerPC (Mac) platforms, as well as others. Linux is open source, which means that it can be changed by a software programmer. Because of its open source nature, many variations of Linux have been created over the years such as Caldera and Red Hat.

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Chapter 2 – Network Operating Systems (NOS) The Macintosh ("Mac") was developed by Apple Computer in 1984. In conjunction with Xerox, they developed what later became known as the mouse and the first GUI display. The Mac OS X is the most current operating system used in conjunction with the Apple computer (at the time of the writing of this book), and the processor used in Apples today is called PowerPC. Macs are known for being used primarily in video or graphic production, but users also use them personally, both at home and on the go.

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Summary Operating systems are the lifeblood of the computer. Without an operating system a computer is just another pile of metal and plastic. Network operating systems allow a computer to function in a network environment. Today, the most popular network operating systems also function as the network operating system. There still are numerous LANs that use a network operating system over a conventional operating system. In a peer-to-peer network, the computers may function as either a server (when sharing resources to others on the network) or a client (when sharing the resources of another computer on the network). In a server-based network, the client computers rely on the server for their resources. Server and client machines typically use different operating systems. Novell’s NetWare allows for client machines to use a variety of operating systems. Windows NT has Server software for the server and Workstation software for client machines. The main advantages of the server-based network are increased security, centralization of administration, and data backups. A key component in a network operating system is the Redirector (called the Requester in Novell NetWare). The function of the redirector is to determine whether a requested resource is located locally (on the client computer) or exists on the server (remotely). The redirector then routes the request to the proper bus accordingly. With the redirector, an application is unaware that it is working from a network. It is important for the networking professional to know the major network operating systems used today, such as Novell NetWare and Windows server operating systems, and at least be familiar with others, (UNIX, Banyan VINES, etc.). Be sure to complete the following exercises and review questions. Study through the chapter again if you need to.

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Chapter 2 – Network Operating Systems (NOS)

KEYWORDS Exercise Keyword

Definition

Client Software CSNW DSMN FAT File Server GSNW Interoperability MHS Linux Macintosh Multitasking NDS Non-Preemptive Multitasking NOS NTFS NWLink Preemptive Multitasking Print Server Redirector/Requester Security Server Software UNIX

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Review Questions

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1.

What is the difference between an operating system and a network operating system?

2.

What is the difference between preemptive and non-preemptive multitasking?

3.

What is the purpose of the redirector?

4.

NetWare is designed as an operating system that will overlay _____________ environments.

5.

What is NDS?

6.

What are the minimum hardware requirements for installing Novell NetWare version 5?

7.

Define interoperability.

8.

Unlike NetWare, Windows NT combines the _____________ and the ___________________ into one.

9.

What is NTFS?

10.

What is a domain?

11.

What are the minimum hardware requirements for Windows NT Server?

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Chapter 2 – Network Operating Systems (NOS) 12.

Name some of the services and protocols that Microsoft included with Windows NT to ensure interoperability with NetWare.

13.

What OS is similar to UNIX and is a publicly open system?

14.

What type of computer was developed by Apple computer in 1984?

15.

What type of network would utilize Windows for Workgroups as an operating system?

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Chapter 3 – The OSI Model and Communication Standards

Chapter 3- The OSI Model and Communication Standards In this chapter you will learn about the OSI (Open System Interconnection) model, what it is and its primary function. You will learn about which layer of the OSI model handles each function, and which devices function at each layer. We will also discuss the IEEE 802 standards as well as touch on various protocols and how they relate to the OSI Model. The OSI model and IEEE 802 Standards are a big part of the Network+ exam.

The Seven Layers of Network Communication The Open Systems Interface (OSI) model is the most commonly referenced standard in the networking industry today. The International Standards Organization (ISO) released a set of specifications for connecting devices on a network in 1978. These specifications were updated in 1984 to what we know today as the OSI model. The purpose of these specifications is to describe how network hardware and software communicate with one another. These specifications allow hardware and software manufacturers to develop products that are compatible with each other. The OSI model is designed as a framework that allows communication between similar and dissimilar computer systems across a network. The OSI Model was created after many of the protocols it represents were already in use. As a result, some of the information regarding these protocols may appear to be inconsistent with the OSI Model. There are seven steps required to prepare data for transmission between the sending application and the receiving application. The OSI model represents these seven steps as seven layers. These layers are used extensively in network environments and it is imperative that the networking professional understand the different layers and their functions. The OSI model defines the rules involving how network devices will contact each other, and how they will communicate if they are using different languages. The OSI model also defines how a device knows when to transmit; when not to transmit; and how to make sure that transmissions are received correctly by the recipient. Even how the physical media is arranged and connected; how the data will flow (at what speed); and how bits are represented on the medium are defined within these specifications.

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The first thing you should notice is we’ve listed the layers from the top down. This model is usually represented in this way because we refer to the layers as upper and lower layers, depending upon their functions.

Seven Layers of the OSI Model The following is a summary of the seven layers of the OSI model starting with the top layer: Application Layer This layer of the OSI Model defines how network services or applications interact with the network. These services include file, print, and messaging services. Error recovery may also be a function of the Application layer. The Application layer is responsible for communication between a user’s application and the network. This is not the actual application or program, simply a support layer that allows an application to use the network by acting as a translator. This is the layer that allows users to send E-mail, transfer files across the network, or access a

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Chapter 3 – The OSI Model and Communication Standards network database. This layer enables computer applications to communicate with applications on remote machines as if they were local. Presentation Layer The Presentation layer is the translator for the network. It translates data into a format that is compatible with the network, and then the Presentation layer of the receiving computer translates the data back into a format that is compatible with the computer. This layer is also responsible for data compression, protocol conversion, (so that an IBM compatible computer may communicate with a Macintosh, etc.) character set conversion, interpreting graphics commands, bit ordering, and data encryption. The network redirector operates at this layer. The redirector is responsible for making network services appear to be local services to a computer. As its name implies, it presents data to the application layer. The presentation layer acts as a translator between an application’s native format and the network. Session Layer The Session layer organizes the flow of data between devices. This layer is responsible for establishing, managing, and ending connections. Each connection is called a session. The Session layer uses a name lookup service such as NetBIOS to identify and establish sessions between two computers. It is also responsible for security and other functions that allow two applications to communicate over the network. The Session layer controls the communication between the two computers and determines who can transmit, or receive, and when. The Session layer organizes data synchronization and also inserts checkpoints in the data. These checkpoints ensure that all data is sent (or received) and make it possible to limit retransmissions in the event of a network failure during transmission. Only the data after the last transmission will have to be retransmitted after a failure. Sessions may be established using simplex, half-duplex, or full-duplex communication. Transport Layer The Transport layer is responsible for the errorfree delivery of the transmitted data. It provides a logical connection between the two devices. The Transport layer is also responsible for packaging, and un-packaging the data for transport. In short, it will break the data into packets, add any addressing information and error correction information, and prepare it for its journey. The Transport layer is responsible for delivering data that is in sequence, without duplication, and error free. The Transport layer accepts packets from the Session layer and repackages them. It is responsible for resizing them before being sent to the destination computer. For example, if the packets are too small, they will be combined. If Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide they are too large, they will be broken into smaller packets. The Transport layer of the destination computer reassembles the data (returns it to its original state) and checks for errors and duplications. Once the data is reassembled, the destination computer will send an acknowledgement that the data was received. The sending computer does not send any more data until it receives the acknowledgement for the previous transmission. If the sending computer does not receive an acknowledgement, it will retransmit after a specified amount of time. When the data is received, it will be un-packed, stripped of its addressing information, checked for errors, and then assembled and sent up to the Session layer. In an ideal world, all data packets will be sent and retrieved in an orderly, error free manner. Should an error occur, however, the Transport layer will sort out the problems and request that missing packets be retransmitted. TCP and UDP are Transport layer protocols. TCP is a connection-oriented protocol. When you are using a connection-oriented protocol, the Transport layer is responsible for the guaranteed delivery of packets. This is accomplished through various error control and other protocol-dependent features. UDP is a connectionless protocol. When you are using a connectionless protocol, delivery of packets is not guaranteed. Connectionless protocols are faster, but connection-oriented protocols are more reliable. Network Layer The hardware that is used to construct the network plays an important role at this layer. The network layer handles all the routing information as packets travel from one network to another. The Network layer is responsible for communication between computers via their IP addresses. This layer makes routing decisions for transmissions that are further away than a single link. It translates logical network addresses into physical machine addresses and determines the best route to the destination computer. This controls network congestion, especially on large intranetworks where there may be more than one way to reach a destination. This layer is also responsible for breaking packets into smaller chunks, if they are larger than the largest acceptable frame size on a network. For example, the largest frame size on an Ethernet is 1,518 bytes and the smallest is 64 bytes. This layer also reassembles the data before passing it up to the Transport layer on the receiving side. Routers and NICs function on this layer. IP and IPX are Network layer protocols. Data Link Layer The Data Link layer is the second lowest layer in the OSI model. It receives a packet from the Network layer and packages it into what is called a frame. Its header includes the hardware address of the sending and destination NIC cards. (These addresses are hardwired onto the NIC by the manufacturers.) It also includes control information such as frame type, segmentation information and routing information. 58

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Chapter 3 – The OSI Model and Communication Standards In addition, the Data Link layer is responsible for error-free transmissions. It adds a trailer to the frame that includes the CRC (Cyclic Redundancy Check). The CRC is simply a calculation that assigns a value to the frame. If the Data Link layer in the destination computer comes up with the same value when it receives the frame, it assumes the data was not damaged in transmission and sends an acknowledgement to the sending computer. If the calculation does not check out, the destination computer will not send an acknowledgement. When the sending computer does not receive and acknowledgement, it will automatically resend the packet. In this way, TCP/IP is somewhat “self healing”. In a broadcast network such as Ethernet, the data is sent out on the wire to all computers. The frame is accepted by the Physical layer of all of the computers on the network and passed up to the Data Link layer. It is the Data Link layer that determines whether the message is for an individual computer or not. If it is, it accepts the data and passes it up to the next layer. If it is not, then it discards the data. The IEEE Committee thought that the Data Link layer needed to be further defined. They accomplished this by splitting the Data Link layer into two sub-layers. Logical Link Control (LLC) The Logical Link Control (LLC) sub-layer of the Data Link layer is the upper of the two sub-layers. It is responsible for connecting two computers on a network and maintaining that link. The LLC sub-layer provides SAPs (Service Access Points) that are used by other computers to transfer information to the upper OSI layers. The Logical Link Control layer is concerned with managing traffic over the physical medium. It identifies a line protocol, such as SDLC, NetBIOS or NetWare and may also assign sequence numbers to frames and track acknowledgements. The IEEE 802.2 standard defines how this takes place. Media Access Control (MAC) The Media Access Control (MAC) sub-layer of the Data Link layer controls the way that multiple computers share the same media channel. The way that a network shares the channel is called its carrier access method. The three main types of access methods are Contention (CSMA/CD & CSMA/CA), Token Passing, and Demand Priority. This sub-layer communicates directly with NICs using the MAC address. The MAC address is another name for the 12-digit (6 byte or 48 bits) hexadecimal address that is hardwired on the NIC by the manufacturer. It uniquely identifies devices on the same medium. The first 3 bytes (6-digits) identify the manufacturer, (they are the vendor code that is assigned to a manufacturer by the IEEE Committee) and the last 6-digits identify the NIC (host). The manufacturer is assigned blocks of numbers to assign to NIC cards. The combination of these numbers assures that each NIC that is manufactured (by any vendor) will have a unique MAC address. Although quite rare, it is not unheard of for these addresses to be duplicated even with these precautions having been taken. MAC addresses are copied to RAM when a NIC is initialized. The following is an example of a MAC address: Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide 00-00-13-35-FD-AB The first 3 bytes (00-00-13) identify the manufacturer of the card. The last 3 bytes (35FD-AB) are the Device ID that is unique to the associated Vendor ID. Bridges operate at the Data Link layer. Bridges are devices that connect network segments and filter data using MAC addresses. Switches, which are intelligent hubs that use MAC addresses to send packets, data work at the Data Link layer of the OSI model. Physical Layer The Physical layer is the bottom layer of the OSI model. It is the only layer of the OSI model that communicates directly with its peer on another computer. It is responsible for the mechanical and electrical functions of transmitting data over a network. It converts the data into the raw bits and signals (1’s and 0’s) that are actually transmitted over the network medium. The Physical layer of the receiving computer converts the bits back into frames. The Physical layer is not concerned with the contents of the packets, it is only concerned with the physical elements of the network and the transmission and reception of signals. It specifies such things as how many pins a network connector will have, and what each one will do. It identifies the NIC, synchronizes the data, and determines when and how data may be transmitted. Point-to-point and multipoint connections are addressed at the Physical layer. Point-topoint communication is the process of one device communicating with one other device . Multipoint communication is the process of one device communicating with multiple devices on a network. Point to point communication is often used between switches and routers on a network. The physical characteristics of a network will affect the specifications of the Physical layer. For example, an Ethernet network using UTP would have different specifications than an Ethernet network using Fiber Optic cable. Repeaters, hubs and transceivers, all operate at the Physical layer of the OSI model.

Note: For more information on the OSI Model, visit www.iso.ch/.

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Protocol Stacks When more than one protocol is necessary to accomplish a task, protocols can be layered so that specific protocols handle their appropriate subtasks at specific layers of the OSI model. These subtasks are stacked in such a way that together they complete a whole task. This is called a protocol stack, or suite. Each protocol receives services from the layer directly below it, and provides services to the layer directly above it. TCP/IP is a common example of a protocol stack. In order for computers to communicate with each other they need to be using the same protocol stacks. In this way even completely dissimilar systems running different operating systems will be able to communicate. Each protocol will communicate with its peer or equivalent on the other computer. Communication Between Peer Layers Most network models utilize this layered architecture. The affect of this layering is that communication is seemingly only taking place between the associated layers of the two computers. Even though the data is passed down through the sending computer’s layers, over the network medium, and up through the receiving computer’s layers, in effect there is a logical or virtual connection made directly between the two associated layers. This is accomplished by each layer (with the exception of the top and bottom layers) adding a header to the message (or removing it on the receiving end) before passing it down (or up) to the next layer. Headers contain instructions for tasks that need to be performed at that level. For example: You send a request for services to the server. You are communicating directly with the Application layer. (Remember, the Application layer is not the actual application, simply a support layer to allow applications to perform network functions.) The request is in the form of a packet. The request is then passed to the Presentation layer where a header is added to the message. The Presentation layer passes the modified packet down to the Session layer, which also adds a header and passes the packet down to the Transport layer. This process continues until the packet reaches the Physical layer. The Physical layer does not add a header, it simply converts the packet into a bit stream and sends it out onto the network medium. When the destination computer receives the data, the process of moving through the layers is reversed. As the packet travels up through the layers, each layer reads and performs the tasks specified in its peer’s header before passing the packet up to the next layer. When it arrives at the Application layer of the destination computer, the data is back in its original form so that it may be interpreted by you and the request is considered processed. In addition to reading the headers and performing the instructions, each layer is also responsible for adding or removing headers so that the data is ready to be interpreted by the next layer.

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Chapter 3 – The OSI Model and Communication Standards Note: Packets (also called service data units) are made up of data and headers acquired from upper layers. Because of this, they are sometimes referred to by different names at different layers. The term packet is appropriate to all of the layers, but the following table lists the other names that might be associated with them at the various layers:

Physical Layer

Signals or Bits or Data Stream into Frames

Data Link Layer

Frames into Packets

Network Layer

Frames or Datagrams into Segments

Transport Layer

Segments into data

Session Layer

Data

Presentation Layer

Data

Application Layer

Data into Data Files or Messages

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OSI and the Real World When working with the OSI model, you must keep in mind that it was created after many popular protocols had already been developed. This means that if you were to attempt to map a protocol or a standard directly to the OSI model, it would not match. In fact, some of the components or layers may actually do the work of several layers of the OSI Model, as in the case of the TCP/IP protocol. Also, the OSI Model is not a protocol. Its purpose is to provide a graphical image of how network protocols work together to provide communication between two computers. By relating various protocols to the OSI model, we can better understand how they communicate across the layers. Data will travel from one computer to another on a network from the Application layer to the Physical layer on the sending computer, then to the Physical layer on the receiving computer and back up to the Application layer. This communication will take place as long as both computers are using the same protocols. The various layers of the protocol are communicating as though they have virtual connections.

As part of the Network+ Certification program, you will need to know the seven layers of the OSI model. The following mnemonics are commonly used to help remember the layers:

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Away

Application

All

Pizza

Presentation

People

Session

Seem

Sausage Throw

Transport

To

Not

Network

Need

Do

Data Link

Data

Please

Physical

Processing

No matter how you memorize the layers, you do need to remember the different layers and the tasks for which each layer is responsible. Keep in mind that it isn’t actually the layer that performs the task, it is the appropriate hardware or software that does the work. The OSI model simply defines which functions need to be completed at each layer and which protocols are to be used at each layer. This is so that different types of computers with different types of hardware and software can communicate. These specifications make it possible for hardware and software manufacturers to create products that will function in different computing environments. The specifications describe how components are supposed to function. Without them we would not have as many software or hardware packages available to us, because each product would have to be specialized towards each type of computer or operating system, etc.

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Devices and the OSI Model As a networking professional, you will usually be working in the first three layers of the OSI model: The Physical layer, Data Link layer and the Network layer. These are the layers that have the most to do with hardware devices and other components that you can change. Programmers usually deal with the upper layers and decide what protocols, etc. are going to be used when they write a program. Repeaters, bridges, routers, and gateways are the most common devices that are used to expand a network. The networking professional needs to be familiar with these devices, as well as where in the OSI model they operate. Repeaters A repeater operates at the Physical layer of the OSI model. It regenerates or amplifies a signal across LANs. As electrical signals travel across a network medium the signal weakens as a result of resistance from the cabling itself. This weakening is known as attenuation. A repeater amplifies these signals so that they can travel further or across LANs. Bridges A bridge operates at the Data Link layer of the OSI model. Bridges connect two separate networks to form one logical network. They rely on MAC addressing to forward messages to their destination. Routers Routers operate at the Network layer of the OSI model. Routers are responsible for using logical addresses to move packets from one network to another and deliver them to a host. Most routers today support multiple protocols such as: TCP/IP

SNAP

SNA

PPP

SLIP

PPTP

X.25

XNS Protocols

IPX/SPX

DECnet

The following is a list of NON-ROUTABLE protocols:

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•

NetBEUI

•

DLC

•

LAT

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Chapter 3 – The OSI Model and Communication Standards Each router has its own table that defines all routes connected to it. Router tables can be entered manually by a network administrator or they can be dynamically updated using routing protocols such as RIP and OSPF. Brouters A brouter operates at both the Data Link and Network layers of the OSI model. It is a device that combines the functions of the bridge and router. If a routable packet is received the brouter will route it using a routing table (make intelligent decisions of how best to route the data). However, if a packet is received from a computer using a nonroutable protocol such as NetBEUI, the brouter will bridge the packet based on its MAC addressing. Gateways Gateways operate in the upper layers of the OSI model (from the Transport to Application layers, but usually in the Application layer). A gateway connects two computer networks that use different protocols or even different technologies. The gateway translates between the two networks so that they may communicate. A computer with special software serves as a gateway and allows for communication between completely dissimilar networks. A popular example is an SNA Gateway, which can be used to connect an IBM mainframe computer to a Microsoft network.

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IEEE 802 Standards In 1980 the Institute for Electrical and Electronic Engineers, Inc. (IEEE) formed a committee to create standards for LANs. This project is known as the 802 project (named for the year and month the project started, February 1980). These standards were prepared before the OSI standards, but the two sets of standards were designed to be compatible. The following table lists the 802 standards by category: (The ones you need to know are the ones in bold!) Number

Defines

802.1

Internetworking

802.2

Logical Link Control (LLC)

802.3

Carrier Sense with Multiple Access and Collision Detection (CSMA/CD)

802.4

Token Bus LAN

802.5

Token Ring LAN

802.6

Metropolitan Area Network (MAN)

802.7

Broadband Technical Advisory Group

802.8

Fiber Optic Technical Advisory Group

802.9

Integrated Voice/Data Networks

802.10

Network Security

802.11

Wireless Networks

802.12

Demand Priority Access LAN, 100BaseVG AnyLAN

If you would like more information on these standards, visit IEEE’s web-site at http://www.standards.ieee.org There are also many other web sites that discuss these standards, and if you would like more information on them, a little surfing might be in order.

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Network Drivers and the OSI Model Just like every other device in a computer, the NIC also needs a device driver to function. The driver allows communication between the operating system and the NIC, and hence, the network. The NIC driver operates at the Media Access Control (MAC) sub-layer of the Data Link layer of the OSI model. Two sets of standards have been developed to define the interfaces between the NIC and the driver. The purpose of these standards is to allow operating system vendors (such as Microsoft and Novell) to write multiple drivers for the same NIC. This way more than one protocol stack can be bound to a single NIC. NDIS (Network Driver Interface Specification) NDIS was co-developed by Microsoft and 3Com Corp. and it defines the interface between the Data Link layer NIC driver and the network transport protocol. It defines a way to bind more than one protocol to a single driver, which will allow a NIC to support multiple protocols. This vendor-neutral interface provides a boundary between a protocol and the driver, which allows any NDIS-compatible protocol stack to function with any NDIS-compatible driver. ODI (Open Data Link Interface) ODI was co-developed by Novell and Apple and serves the same purpose as NDIS, but is designed for use with Novell NetWare and Macintosh environments. However, NDIS and ODI are incompatible with one another.

Protocols and OSI Protocols are the rules that govern communication between computers. The protocols used to communicate in a network environment are called protocol suites or stacks. This is because of the way they work within the OSI layers (on top of one another). Network 70

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Chapter 3 – The OSI Model and Communication Standards protocols are responsible for addressing and routing communication over a network. They also handle error checking and acknowledgments of transmitted data. Network protocols work at various layers of the OSI model. It is the protocol operating at a certain OSI layer that defines that layer’s function. Application layer protocols provide support for application-to-application functions in the upper layers of the OSI Model. Transport layer protocols reside in the middle layers of the OSI model and are responsible for establishing sessions and ensuring that data is sent and received error free, and in full. Network protocols reside in the lower layers of the OSI model and handle the addressing and routing functions of network communication. The network layer protocols also are responsible for error checking (CRC) functions. Protocol Binding In order to function, a protocol must be bound to the NIC. This binding process is what links the protocol stacks to the NIC driver. It is possible to bind two protocols to one NIC (such as TCP/IP and IPX/SPX) or to have two NICs with one protocol bound to each one. (This is useful if your network communicates with another entirely dissimilar network.) The order in which these protocols are bound to the NIC determines which one the network operating system will attempt to use first. For example, if TCP/IP is bound first, the operating system will attempt to communicate using TCP/IP first. If that fails, it will then attempt to communicate with the second protocol. Connection-Oriented vs. Connectionless Communication between computers may be connection-oriented or connectionless. Connection-oriented would be like dialing up your friend to ask them to come to a party. You speak directly to your friend who either agrees or disagrees to come. In a connectionless scenario, it would be like calling your friend and simply leaving a message on his answering machine. You have no confirmation (unless he calls you back) that he received the message. In connection-oriented communication, the sending and receiving computers actually establish a connection to communicate. The receiving computer acknowledges that it received the data that was sent. This form of communication protocol guarantees the delivery of data. In a connectionless communication, the data is simply sent and assumed to be received. There is no guarantee that the message was delivered. Connectionless communication is faster, but connection-oriented is more reliable. Routable vs. Non-Routable Protocols In the early days of networking, LANs were usually just one network that served a single company or department. In today’s LANs however, it is not uncommon for more than one LAN to be connected using a router. Protocols that are able to route messages across these devices are called Routable. Protocols that are unable to send messages across routers are called Non-Routable.

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Network + Training & Test Preparation Guide The following is a list (in alphabetical order) of some routable protocols: •

AppleTalk

•

DECnet

•

IPX/ SPX

•

PPP

•

PPTP

•

SLIP

•

SMB

•

SNA

•

TCP/IP

•

UDP

•

X.25

•

XNS Protocols

The following is a list of NON-ROUTABLE protocols: •

DLC

•

LAT

•

NetBEUI

Non-routable protocols cannot be used in routed environments (such as the Internet). It is important that the networking professional know the difference between routable and non-routable protocols and which protocols are routable. Networking Protocols and Stacks The following are common routable networking protocol stacks. As a networking professional, you should be familiar with these protocol stacks and you should know the OSI layer in which their components function.

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AppleTalk This proprietary protocol stack allows Macintosh systems to operate in a network environment. This stack consists of: •

AppleShare – Provides Application layer services for Macintosh.

•

AppleTalk Filing Protocol (AFP) – Manages file sharing at the Application layer

•

AppleTalk Transaction Protocol (ATP) – Provides connection between two computers at the Transport layer.

•

Datagram Delivery Protocol (DDP) – Provides transmission of packets across a network. It resides in the Network layer.

DECnet This is Digital Equipment Corporation’s protocol stack. It is a routable protocol that can also use TCP/IP and OSI protocols. IPX/ SPX This protocol is the proprietary protocol that was developed by Novell for Netware servers and clients. It has been modified over the years and now contains the following components: •

IPX (Internetwork Packet Exchange) – Works on the Network layer of the OSI model and provides connectionless service. It uses the MAC address and is non-routable. (If data must cross a router SPX is used.)

•

SPX (Sequenced Packet Exchange) – Is a Transport layer protocol and is a connection-oriented protocol. It is a routable protocol.

•

MLID (Multiple Link Interface Driver) – Resides in the Data Link layer in the MAC sub-layer. This is the NIC driver in the IPX/SPX suite.

•

LSL (Link Support Layer) – Also resides at the Data Link layer and provides the interface between the MLID and the upper layers.

•

RIP (Routing Information Protocol) – This is a simple routing protocol that counts the hops needed to reach a destination. It chooses the route with the fewest hops, regardless of speed. It resides in the Network layer.

•

NLSP (NetWare Link Services Protocol) – This Network layer protocol is also a routing protocol. In addition to hop count, this protocol takes into consideration link speed and network traffic to make more efficient routing decisions than RIP.

•

NCP (NetWare Control Protocol) – This control protocol resides at four different layers of the OSI model, and handles file and print services. At the Application layer it handles application interfaces. At the Presentation Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide layer it handles data translation. At the Session layer it establishes and controls sessions. At the Transport layer it handles sequencing, flow control, and connection-oriented error control services. •

SAP (Service Access Protocol) – This Application layer protocol is used on servers to broadcast (at specified intervals) the location and services that are available from that server.

•

NWLink – This Transport layer protocol is Microsoft’s version of IPX/SPX. It is routable and provides support for NetBIOS names.

Many companies use Netware with the TCP/IP protocol stack. Novell Netware 5.1 and later installs TCP/IP by default. SMB (Server Message Block) This Microsoft protocol operates at the Presentation layer and is used for communication between the server and the redirector. SNA (Systems Network Architecture) This protocol suite is used with IBM mainframes and AS/400 systems. The two main protocols in this stack are APPC (Advanced Peer-to-Peer Communications) and APPN (Advanced Peer-to-Peer Networking). APPC supports Transport and Session layer services, while APPN provides Network and Transport layer connections. TCP (Transmission Control Protocol) The TCP/IP suite contains two major protocols, TCP and IP. It also contains several others that the networking professional needs to be familiar with. We will cover TCP/IP extensively in Chapters 8 & 9. TCP functions at the Transport layer of the OSI model and is a connection-oriented protocol. TCP is responsible for adding header information that contains error checking and flow control information. IP (Internet Protocol) IP is a connectionless protocol. It operates at the Network layer of the OSI model and is responsible for addressing packets and routing them over the network. UDP (User Datagram Protocol) UDP provides the datagram service in TCP/IP. A datagram is a kind of packet that has minimum overhead. No error checking exists and delivery is not guaranteed, so the application must do the error checking and retransmission if necessary. Missing packets and out-of-sequence data is not checked and no acknowledgements are sent. It is faster than TCP because it is connectionless. It is also layered on IP like TCP. FTP (File Transfer Protocol) This protocol is used for file sharing between computers on a TCP/IP network. FTP is an Application layer protocol and is available for nearly every operating system. It is used to upload and download files on the Internet and between two computers.

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Chapter 3 – The OSI Model and Communication Standards TFTP (Trivial File Transfer Protocol) Trivial File Transfer Protocol (TFTP) is used for transferring files quickly and more simply than the File Transfer Protocol (FTP). It is less capable than FTP because it uses UDP rather than TCP, making it connectionless. If you do not need to use passwords, then TFTP would be advisable over FTP. Telnet This Application layer protocol allows a user to log on and run applications remotely. The local computer acts as a display only and all processing occurs remotely. Telnet can also be used for remote configuration of servers and network devices such as routers and switches. NFS (Network File System) Sun Microsystems developed NFS as a file and drive sharing system. It operates like a combination of Telnet and FTP and allows users to access files and drives on remote computers as if they were local resources. It is an Application layer protocol. SMTP (Simple Mail Transfer Protocol) SMTP is an Application layer protocol that is responsible for sending E-mail from the sender’s server to the recipient’s E-mail server. RIP (Routing Information Protocol) RIP (Routing Information Protocol) – This is a simple routing protocol that counts the hops that will be needed to reach a destination. It chooses the route with the fewest hops, without regard to speed. It resides in the Network layer. NTP (Network Time Protocol) Network Time Protocol (NTP) is used in a networked environment to synchronize computer clock times. It uses Coordinated Universal Time (UTC) to synchronize computer clock times to a millisecond. It is designed to be reliable and allows for scalability. OSPF (Open Shortest Path First) Like RIP, this is also a Network layer protocol. OSPF counts the number of hops to the destination computer, but in addition, it also takes into consideration the network speed and traffic and makes routing decisions based on the best route, instead of only the number of hops. ARP (Address Resolution Protocol) ARP is responsible for resolving IP addresses to MAC addresses. ARP keeps a table of corresponding IP and MAC addresses that have been resolved in the previous 10 minutes. ARP will first check its table and if a matching address is not found, it will broadcast on the local subnet to determine the MAC address of the computer with the associated IP address. The computer that has the corresponding IP address will respond to the broadcast by sending its MAC address. ARP will add the information to its table for future use. RARP (Reverse Address Resolution Protocol) is a related protocol that performs the same function, but in reverse. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide X.25 X.25 is a packet switching protocol that is sometimes referred to as a public data network (PDN) because it is sometimes used by more than one organization. This is really a type of network that is owned by telephone companies who charge organizations for use. It uses standard telephone lines and switches, which can be unreliable due to the quality of phone lines. In addition, X.25 is also an equipment specification. The first specification refers to the DTE (Data Terminal Equipment). This is the host on an X.25 network. The second part of the specification is the DCE (Data Communications Equipment). The DTE acts as an endpoint for communications and the DCE acts as an entry point for the DTEs. This is an older packet switching network that uses switches and circuits. Data is routed via the best connection at a given time. This means that routes change as conditions change. Packets from the same transmission are routed via the best route (and don’t necessarily follow the same route) and are reassembled at the receiving end. At each stop, packets are re-examined to determine whether they are damaged, making X.25 a very slow but very reliable protocol. Because of this, the X.25 network is sometimes referred to as a cloud. Data goes in and comes out, but in between, it is out of the administrator’s control. X.25 functions take place at the Physical and Network layers and normally interface with a protocol called LAPB (Link Access Procedures-Balanced). XNS (Xerox Network System) XNS is a proprietary protocol developed by Xerox for their Ethernet LANs. It is bulky and slow and has largely been replaced by TCP/IP. Non-Routable Protocols The following protocols are non-routable. This means that they may not be used with networks that use routers to connect multiple LANs. This also means that they may not be used to connect to the Internet. DLC (Data Link Control) DLC operates at the Data Link layer of the OSI model. It was originally used to connect IBM mainframes to HP network printers. This protocol is not used for data communication. Instead, it is installed only on the print server and communicates directly with the printer. This is not an actual protocol and is not used to perform networking functions, only printing functions. LAT (Local Area Transport) LAT does not have a Network layer, which is the main reason that it is non-routable. It is a DEC protocol used for interactive, asynchronous terminal traffic over a LAN. It is typically used between a DECserver and a VAX minicomputer.

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Chapter 3 – The OSI Model and Communication Standards NetBEUI (NetBIOS Extended User Interface) This non-routable protocol works at the Transport layer of the OSI model. It is fast, easy to configure and small, which is an advantage if using older MS-DOS-based systems. It may be used with bridges, but is primarily used today for backward compatibility with existing networks.

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Network + Training & Test Preparation Guide Other Protocols The following are other protocols with which you should be familiar: SLIP (Serial Line Internet Protocol) SLIP supports TCP/IP connections made over serial lines. It does not support IPX, NetBEUI, or DHCP. SLIP requires static IP addressing and doesn’t support data encryption. SLIP is not used as much as PPP. PPP (Point-to-Point Protocol) This protocol was developed to replace the SLIP protocol and alleviate some of its limitations. PPP supports IPX, NetBEUI, DHCP, and other protocols as well as TCP/IP. It also supports data encryption. PPTP (Point-to-Point Tunneling Protocol) This is an extension to the PPP protocol. The main improvement is that it allows clients to connect remotely over the Internet. PPTP encapsulates TCP/IP, NWLink and NetBEUI, enabling it to use the Internet as a backbone for NWLink and NetBEUI. Users can establish secure encrypted access to their corporate networks via Virtual Private Networks (VPNs) that PPTP establishes. SNMP (Simple Network Management Protocol) Devices using TCP/IP use SNMP for controlling network communications. This management protocol interfaces with network analyzer software making it easier to manage complex networks. SNMP is used extensively with intelligent hubs. ISO/OSI Standard This is a complete standard with each layer having a protocol (or protocols) mapped directly to it. It provides full networking functions at every layer of the OSI model. ICMP (Internet Control Message Protocol) ICMP is used in error-handling and control procedures. It operates at the Network layer of the OSI model and performs connection services and flow control services. Like a traffic report on your radio, it detects congested areas and links that are down, and notifies upper layers to route around them. DNS (Domain Name System) DNS translates names that humans understand into names that the computer understands. It maintains a database and provides hostname to IP address resolution. This database is typically dynamic in today’s modern networks, but it can also be modified manually by the network administrator. XDR (External Data Representation) XDR handles translation and operates at the Presentation layer. It provides machineindependent data translations that may include encryption and data descriptions. RPC (Remote Procedure Call) RPC operates at the Session layer of the OSI model. It handles session establishment, administration, file transfers, and connection release. RPC is used by the redirector to 78

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Chapter 3 – The OSI Model and Communication Standards determine if a resource is local or on the network. It makes the remote resources appear local to the computer. Note: TCP/IP is such an important protocol that we will be covering it in depth later in the text.

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Summary In this chapter, we learned about the OSI model and its importance in networking. We also learned what type of devices function at various levels of the OSI model and how these devices interact with each other. It is important to note that memorizing the OSI model will not only help you pass the test, but also help you to narrow down problems when troubleshooting a network. For example, if you can get to the server through a router, you know that networking is taking place and that you have functionality up to layer three. The OSI model is an invaluable tool to the networking professional.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book. Keyword

Definition

802.x Standards Application Layer Bridge Brouter Data Link Layer Gateway LLC (Logical Link Control) MAC (Media Access Control) Network Layer Non-Routable Protocol OSI Physical Layer Presentation Layer Protocol Stack Repeater Routable Protocol Router Session Layer Transport Layer

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Review Questions – Chapter 3 1. Who developed the OSI model?

2. Name the seven layers of the OSI model.

3. A network adapter card operates at the _____ layer of the OSI Model.

4. A bridge operates at the ________ layer of the OSI model.

5. A router operates at the _________layer of the OSI model.

6. Data compression takes place at the __________ layer of the OSI.

7. Which OSI layer is responsible for the MAC address?

8. What is the function of the Application Layer?

9. The ____________ layer is responsible for the mechanical and electrical functions of transmitting data over a network.

10. What is the function of the Presentation Layer?

11. Which OSI layer is responsible for establishing, managing, and ending connections?

12. What is a MAC address?

13. Which part of this MAC address is the Device ID? 00-01-A5-D3-B4-01 82

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Chapter 3 – The OSI Model and Communication Standards 14. Which OSI layer makes routing decisions?

15. Which OSI layer is responsible for delivering data in sequence, without duplication and error free?

16. The Data Link layer has been split into two sub-layers. What are they?

17. What is the function of a Gateway?

18. Which IEEE standard defines the Logical Link Control (LLC) sub-layer?

19. What are NDIS and ODI?

20. Describe protocol binding.

21. Which is faster, connection-oriented communication or connectionless communication?

22. Name as many routable protocols as you can remember.

23. You have expanded your NetBEUI network into two segments and are using an intelligent router to optimize network traffic. Will this work? Why or Why not?

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Chapter 4 – Hardware Media and Peripherals

Chapter 4 - Hardware Media and Peripherals This chapter explores network media, and the hardware aspect of network operations. There are several cabling options, which we will address here, along with connectors, network adapter cards, and other hardware and peripherals. The effect of hardware on network performance will be key to your networking operation. Understanding how different network topologies interact with different types of cable is essential. How to properly configure and use network adapter cards, and how wireless networks function are among the topics we will cover in this chapter.

Network Cabling Although wireless networks do exist, (and we’ll cover them later in this chapter), most networks utilize some type of cable to carry transmissions on the network. There are numerous kinds of cable, but fortunately for the networking professional there are only three major types that you need to understand. Coaxial Cable Coaxial cable consists of a copper core (either solid or stranded) surrounded by plastic foam insulation, a braided metallic shield called the ground as well as an outer cover. Because it is shielded, it is less susceptible to EMI than UTP. Coaxial cable is used in Ethernet Networks; 10Base2 (Thinnet) and 10Base5 (Thicknet) in a Bus topology. It can transmit voice, video, and data over longer distances that UTP or STP. Thinnet Thinnet is about ¼-inch thick and is flexible and easy to install. It has a maximum segment length of 185 meters (about 606 feet) and a transmission speed of 10 Mbps. It uses a BNC (British Naval Connector) “T” connector to connect directly to the NIC. It is not often used in today’s networks, but may still be used in some temporary installations such as a construction trailer (although wireless would be a much more likely alternative). Thicknet Thicknet is about ½-inch thick and fairly rigid. Its copper core is thicker than Thinnet and can carry signals farther (maximum segment length is 500 meters or about 1650 feet). It also has a transmission speed of 10 Mbps. It uses a device called a transceiver to connect the Thicknet cable to the NIC via a drop cable. The drop cable is connected to the NIC’s AUI (Attachment Unit Interface) port connector, or DIX (Digital, Intel, Xerox), which is more commonly known as a DB-15 connector.

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Network + Training & Test Preparation Guide Because it is thicker than Thinnet, it is not as easy to install. In the past, Thicknet was used as a backbone to connect several Thinnet networks. In today’s networks, it has been replaced by twisted-pair cable and fiber optic cable. Summary of Coaxial Cables Not all coaxial cables are the same. They are specified based on their impedance. Impedance is a unit of measurement for resistance to AC voltages. It is expressed in ohms. In order for the network to operate at peak performance, all electronic components must operate at the same impedance. Using the wrong cable will cause poor performance and/or failure of the network.

Uses

Type

Impedance – Ohms

10Base5 Thicknet

RG-8

50

10Base5 Thicknet

RG-11

50

10Base2 Thinnet

RG-58

50

Cable TV

RG-59

75

ARCnet

RG-62

93

Coaxial Connectors British Naval Connectors (BNC) are used in both Thinnet and Thicknet networks to connect the cable to the computers. As a networking professional you will need to be familiar with the different types and their uses, as well as how they are attached to the cables. BNC Cable Connectors BNC T Connector The BNC T connector is used to connect the network interface card to the cable. It is attached directly to the NIC but allows network signal to flow straight through it as well as to the NIC.

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Chapter 4 – Hardware Media and Peripherals BNC Barrel Connector The BNC barrel connector is used to connect two lengths of Thinnet cable together. It is soldered or crimped onto the cable to make the connection. BNC Terminator Both ends of the cable must be terminated to absorb signals and eliminate signal bounce. The BNC terminator is a connector that has a resistor built in that performs this function. One of the terminators must be grounded.

N Connectors Thicknet uses N connectors that screw on. Both ends of the cable need to be terminated with one end grounded.

Transceivers The computers in a Thicknet network do not connect directly to the cable as with Thinnet. Thicknet uses a device called a transceiver. A transceiver is a device that transmits and receives signals on a network medium. The transceiver has a port for an AUI connector (AUI port connectors are also called DIX connectors or DB-15 connectors), and an AUI cable. This cable is called a drop cable or a transceiver cable, and is used to connect the device to the network. It is common to connect a Thinnet LAN to a Thicknet backbone using a transceiver.

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Vampire Taps Although transceivers can be connected by cutting a cable and splicing N connectors and T connectors on the transceiver, this was time-consuming and it absorbed signal so it was not the common approach. Instead, most networking professionals used a clamp-on transceiver. These clamp-on transceivers were often referred to as vampire taps because they utilized sharp teeth that punctured the cable to make the connection. This types of connections have been largely replaced by newer cable methods such as twisted-pair and fiber optic cable.

Twisted-Pair Cable Twisted-pair cable has become the most popular type of cable used in networks today. It is flexible and easy to install and is the least expensive of all the cable types. This cable type consists of insulated pair strands of copper wire that are twisted around one another. There are four pair strands in most twisted-pair cables. The twist helps 88

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Chapter 4 – Hardware Media and Peripherals prevent crosstalk and sensitivity to EMI. There are two types of twisted-pair cables: Unshielded Twisted-Pair (UTP) and Shielded Twisted-Pair (STP). The telephone wire we have all seen in our homes is an example of twisted-pair cabling. UTP Unshielded Twisted-Pair (UTP) cabling is the less expensive of the twisted-pair cable types and hence the most popular. Since it is unshielded, it is more sensitive to EMI. It has a maximum segment length of 100 meters. The quality of UTP is based on the number of twists per meter in each pair of wires. The tighter the twist, the faster the signal can be sent through the wires without crosstalk. Currently, there are six categories. Category 3 cabling has a transmission speed of 10 Mbps. Category 5 UTP has a transmission speed of up to 100 Mbps. UTP wire typically consists of eight wires or four pairs. The following is a summary of UTP cables.

Category

Maximum Data Rate

Uses

1

Less than 1 Mbps

Doorbell Wiring

2

4 Mbps

Token Ring and Voice

3

16 Mbps

10BaseT and Token Ring

4

20 Mbps

Token Ring

5

100 Mbps

ATM and Gigabit Ethernet

5e

1000 Mbps

ATM and Gigabit Ethernet

6

1000 Mbps

Extremely fast broadband

STP Shielded Twisted-Pair (STP) cabling is insulated with a foil mesh between the wire pairs. This results in less sensitivity to

EMI.

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Network + Training & Test Preparation Guide Twisted-Pair Connectors UTP and STP are usually connected with RJ-45 connectors. An RJ-45 connector looks just like a common telephone jack (RJ-11) only larger. An RJ-11 jack has four connection points where an RJ-45 jack has eight.

AppleTalk AppleTalk networks utilizing STP cabling uses a DIN-type (DB-9) connector. Distribution Panels Distribution racks and shelves are sometimes used to create more room for cables when floor space is at a premium. This is an excellent way to organize network cables. Expandable patch panels (sometimes called punch down blocks) are also used with UTP installations. They come in various sizes up to 96 ports and support transmission speeds of up to 10 Gbps . These patch panels act like a switchboard where cables are connected and organized. The wire is assembled in the back of the patch panel in what is called the pin location. The pin location is a color-coded slot into which the wire is punched down using a special tool punch down tool to make the proper connection by stripping the insulation from the wire without breaking the wire. The front of the patch panel contains RJ-45 ports (a port is a female counterpart for the RJ-45 jack). The RJ-45 jack’s position can therefore be changed from patch panel to patch panel to use a different set of cables for the same connection. This gives the network administrator a greater degree of flexibility and provides fault tolerance for the network cabling system. Wall plates are typically used to make the connection to the computers themselves.

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Chapter 4 – Hardware Media and Peripherals Fiber-Optic Cable Fiber-optic cable is the ideal cabling for networking. It supports extremely high bandwidths and is not subject to EMI.. It also supports much longer segment lengths (several miles). However, as it is the most expensive and most difficult to install of all the cabling types, it is therefore not as common as UTP. . Fiber-optic cable consists of a glass core surrounded by a coating of cladding (layer of glass or plastic). This cladding reflects the signal back into the fiber, which reduces signal loss. (The core can also be made up of plastic, which is easier to install, but plastic core fiber-optic cannot carry the signals as far as glass.) Because data only passes in one direction over fiber-optic cable, it consists of two separate strands enclosed in a plastic jacket for strength. One strand transmits and one receives. Signals are sent along the cable as pulses of light.

Because data is transmitted as light and not as electrical impulses, the data cannot be tapped or stolen. Because of this feature, fiber-optic is used in networks that need a secure media that transmits at high speeds over long distances. IBM Cabling IBM has its own special cabling for use on their Token Ring networks. They do not conform to the same specification as used with standard UTP. IBM cabling is based on its Type. The following is a summary of IBM Types:

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Network + Training & Test Preparation Guide

Type

Wire Specs

Uses Connect between terminals and distribution boxes or between different wiring closets.

1

Two STP solid core 22 AWG wires – maximum length 101 meters (331 feet).

2

Six twisted pairs, two STP and four UTP – maximum length 100 meters (328 feet).

Same as type 1 but adds voice capability along with data.

3

Four UTP with two twists per inch – 22 or 24 AWG wire – maximum cable length is 45 meters (148 feet).

Lower cost alternative to type 1 or 2. Cannot be used for 16 Mbps Token Ring.

4

Not Defined

5

Two 62.5/125-micron multimode fibers.

Fiber Optic

6

Two STP – 26 AWG Wire

Data patch cables.

7

Not Defined

8

Two STP – 26 AWG Wire

Contains a shield for use under carpets.

9

Two STP –26 AWG Wire

Plenum grade.

IBM has developed its own cabling complete with its own standards and specifications. The connector that they developed is unique in that any connector can connect to another as opposed to having “male” and “female” connectors as with other types of connectors. An IBM connector is sometimes called a hermaphrodite. These are very rarely used in today’s modern networks.

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Chapter 4 – Hardware Media and Peripherals Summary of Cabling The following table summarizes the specifications for network media: Media

Bandwidth (Mbps)

Nodes/ Segment

Maximum Nodes per Network

Maximum Cable Length (meters)

UTP

4-100

1

1024

100

STP

16-155

Varies

260

100

Coaxial Thicknet

10

100

300

500

Coaxial Thinnet

10

30

90

185

Fiber Optic

2000

1

1024

2000

Infrared

1-10

NA

Varies

32

Note: We will discuss Infrared later in this chapter.

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Cabling Terms The following are terms that you will encounter when working with network cabling: AWG (American Wire Gauge) AWG is the standard that describes wire thickness. As the AWG wire number decreases, the wire thickness increases. For example, 10-gauge wire is heavier than 14-gauge wire. Typical STP and UTP wires are 24-gauge. Bandwidth Bandwidth is a term used to measure the ability of a network medium to transmit data. Bandwidth is measured in megabits per seconds (Mbps) or gigabits per second (Gbps).Baseband vs. Broadband There are two techniques that are used to transmit signals over cable: •

Baseband uses the entire capacity of the cable as a single channel. It is used with digital and utilizes TDM (Time Division Multiplexing). The signal flow is bidirectional.

•

Broadband allows two or more channels to share the bandwidth of the cable or medium. It is used with analog and utilizes TDM (Frequency Division Multiplexing). The signal flow is uni-directional.

Simplex vs. Duplex •

Simplex refers to one-way communication only. For example, a pager can receive a message, but cannot send a message.

•

Half-Duplex can send transmissions both ways, (send and receive) but only one at a time. An example would be a CB radio transmission where only one person can talk at a time.

•

Full-Duplex allows for two-way simultaneous transmissions. For example, the telephone utilizes full-duplex transmissions. Both you and the party you are talking to can talk and listen at the same time.

Plenum Grade Cabling A plenum is the space between the ceiling and the floor above. This space is used to circulate air through a building. Because this space does circulate air through a building, fire codes are very specific about what types of cabling can be run in this space. Coaxial cable comes in two grades: Polyvinyl Chloride (PVC) and Plenum. PVC is used for the outer cover and the insulation in Polyvinyl Chloride grade cabling. PVC grade cable is less expensive than Plenum grade cable but it gives off poisonous smoke and gas when burned. If this type of cable were used in the plenum, these fumes would circulate throughout a building in the event of a fire.

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Chapter 4 – Hardware Media and Peripherals In contrast, Plenum grade cable is insulated and jacketed in special materials that give off a minimum amount of smoke and fumes. It is therefore specifically designed to be used in these circulation areas. A networking professional must be aware of local fire codes regarding plenum cabling.

Selecting Cables As a networking professional you will need to determine which kind of cabling medium to use for a given network. There are many factors that you must consider if you are to meet your networking objectives, such as: •

Budget

•

Network Traffic

•

Security Needs

•

Size/Distance

•

Environment

The installation parameters need to be considered as well. For example, how will the cable need to be installed? (If there are tight corners, the flexibility of the medium should be considered.) Will plenum grade cable need to be purchased? (If installing cabling in the plenum, local fire codes will need to be addressed.) Will the cable be installed in “noisy” areas where EMI will be a factor? (If installing the cable near equipment or fluorescent lighting, shielded cable or fiber optic cable might be more appropriate.)

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Network + Training & Test Preparation Guide How long will the cable runs need to be? (If the network will be small, there is no need to use heavy duty cabling when another type would be more cost-effective. On the other hand, attenuation could have an affect on network performance if you use cabling on a large network where long cable runs are a factor.) If security is an issue on the network and the data to be transmitted needs to be secure, fiber-optic cabling might be appropriate to avoid any tapping. Is future growth of the network expected? (Expandability for future growth is easier to achieve if it is planned for in advance.) Transmission speeds and, last but not least, cost are issues that will need to be addressed when planning your network. Building a low-cost network that doesn’t do the job won’t win you any brownie points in the long run!

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Chapter 4 – Hardware Media and Peripherals

Network Interface Cards (NICs) Network Interface Cards or NICs, are also known as Network Adapter Cards. NICs are used to connect the computer to the network. The purpose of this card is to translate the data that the computer can understand into signals that can be transmitted over the network medium. (And of course to translate it back again.) This card is installed into an expansion slot on every computer on the network and the cable is connected to the card’s port. It makes the physical connection to the network, handles network addressing, and controls the flow of data on the network. Preparing the Data Computers carry data internally via data pathways called buses. Because these paths are side-by-side, data is moved along in groups. This is known as parallel communication. Network cabling moves data in a single data stream. This is known as serial communication. Data traveling via a computer’s bus is traveling in parallel because the bits are traveling along side-by-side. Older computers had 8-bit buses which meant that data could be sent 8-bits at a time. Today, most buses are 16-bit or 32-bit. We’ll discuss the different data bus architectures a little later. The NIC takes data coming from the computer in parallel form and converts it into serial data so that it can be sent along the network cable. Signals and Clocking In order to understand how a NIC works, you need to have a basic understanding of signals and clocking. Signals There are two types of signals: Analog: Signals or waveforms that frequently take the form of sine waves, which constantly vary in one or more values. Analog data has an infinite number of possible states. Digital: Signals that are simple 1’s (on), or 0’s (off). Clocking Clocking is the method used by the NIC to count and pace the number of signals that it sends and receives. Signals are sent in a continuous flow that represents the start and stop of a data frame. This is how the NIC keeps track of how much data has been sent or received.

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Network + Training & Test Preparation Guide Network Addressing/MAC Address The NIC is also responsible for encoding the signals it sends out on the network medium with its unique MAC address. This informs the other computers on the network of its location. Each NIC has a unique address that is hardwired onto it by the manufacturer. The IEEE (Institute of Electrical and Electronics Engineers) committee assigns blocks of these unique numbers to each manufacturer. DMA (Direct Memory Channel) The NIC must be able to communicate with the computer in order to prepare data for transmission on a network medium. Most computers utilize Direct Memory Access (DMA) and the computer assigns some of its memory space for use by the NIC. DMA allows the NIC to access the computer directly without having to go through the CPU. This makes transferring data much faster. The NIC signals the computer to send the data that it wants to transmit and the computer’s bus moves the data from memory to the NIC. Data often moves faster than a NIC can process it. When this occurs, the data is sent to the card’s RAM (buffer) until it can be processed. Controlling the Data Flow Before transmitting, a NIC will send data over the network to the receiving card. This communication takes place so that both the sending and receiving cards can agree on data flow and confirmation parameters. Before transmission actually takes place the NICs agree on the following points: •

The maximum size of the groups of data to be sent.

•

The amount of data that will be sent before a confirmation.

•

The time intervals between data chunks.

•

The amount of time between confirmations.

•

How much data each card can hold before overflow occurs.

•

The speed of the transmission.

If one card is faster or more sophisticated than another card, they agree on common parameters so that the data is sent at a speed that can be handled by the slowest card. Once all of these parameters are agreed upon, the two cards start sending and receiving data. Configurable Options In order for the computer to communicate with the NIC, the NIC may need to be configured. Plug-and-Play cards configure themselves to be compatible with the 98

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Chapter 4 – Hardware Media and Peripherals operating system so that they may utilize the system’s resources. Other cards will need to be configured manually. Some of these settings are configured by using DIP switches or jumper settings, and some are set using software. The operating system and the NIC need to have compatible resource settings, such as: IRQ (Interrupt Request) The Interrupt Request (IRQ) line is used by the NIC (and other devices) to contact the CPU. These IRQ lines are part of the system hardware and each device needs its own line. In practice, certain IRQs are almost always used for specific devices. Having an IRQ conflict (more than one device sharing an IRQ) can cause problems. Typically IRQ5 is used for the network adapter card. IRQ3 and IRQ15 may also be used if IRQ5 is already assigned. The main concept to understand is that the NIC is set up to use an IRQ that is not already assigned to another device. Check your system’s documentation to determine its current IRQ settings. The most important thing to remember about IRQs is that typically no two devices can use the same interrupt. See Appendix A for common IRQ assignments. Base I/O Port Address This is the channel through which data flows between a computer’s hardware (like a NIC) and the CPU. The device is constantly listening to this channel for commands from the processor. Each device must have a unique base I/O port number. These hexadecimal port numbers define a channel between a device and the processor. Check your system’s documentation for assignment and availability of base I/O port addresses. Base Memory Address The base memory address marks the location in a computer’s RAM of the beginning of the buffer area that is reserved for use by a device, in this case the NIC. This is sometimes referred to as the RAM start address. This buffer area is used to store incoming and outgoing data frames. Some NICs have settings that allow you to specify the size of the buffer, while others do not use RAM addresses at all. See Appendix A for common address assignments. DMA Channel Configuration of Direct Memory Access (DMA) channels is similar to IRQs. The main difference is that there are only eight DMA channels available. The good news is that unlike an IRQ, not all devices need one. DMA channels are used by devices that frequently need access to large amounts of memory. With a DMA channel, these devices can access the memory that they need without interrupting the processor. Only devices like NIC cards that need this type of memory access are assigned DMA channels. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Ring Speed In Token-Ring networks the ring speed must be set on the NIC. The two speeds available are 4 Mbps or 16 Mbps. If the correct ring speed is not set a computer will not be able to connect to the network and may even cause the network to fail. Connector Type Your NIC may automatically adjust to use the kind of connector that you are using (BNC, RJ-45, or both), or you may have to configure it manually. Wireless NICs Wireless NICs are used to connect wireless network systems to the computer. They usually use a type of antenna (omnidirectional) and an antenna cable. Special software is usually needed to connect a wireless NIC. Wireless LANs are discussed later in this chapter. Fiber-Optic NICs Due to the high-cost of fiber-optic adapter cards, they are usually only used in special cases where high-speed direct computer to fiber-optic cable connections are required.

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Data Bus Architecture A data bus is a group of parallel conductors (circuit traces) found on the motherboard that is used by the CPU to send and receive data from all the devices in the computer. Standard Bus Types There are six data bus architectures found in Intel-based computers: The Industry Standard Architecture (ISA) is an 16-bit bus. The Extended Industry Standard Architecture (EISA) is a 32-bit bus. Micro Channel (MCA) is a 32 bit bus. The Peripheral Component Interconnect (PCI) is a 32-bit bus, but can be a 64-bit bus. Micro Channel is a data bus developed by IBM that requires licensing to be used by manufacturers and isn’t used much. Today most buses are either EISA or PCI. Laptops PCMCIA (Personal Computer Memory Card International Association) are credit card sized expansion buses that are used in portable computers. They are also called PC-Card Buses. With this card comes the same expandability enjoyed by desktop PCs, including network connectivity. They are generally 32-bit buses.

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Network Performance Because of the effect that the NIC can have on network performance, it is important that it is configured correctly and optimally. Most cards offer features that are designed to improve network performance: Utilizing Direct Memory Access (DMA) improves network performance by allowing the computer to move data directly to the NIC’s buffer without going through the CPU. Shared Adapter Memory is a method by which a NIC contains RAM that it shares with the computer as if it were actually installed in the computer. Shared System Memory is a method by which the NIC utilizes a portion of the computer’s memory to process data. Both EISA and MCA NICs offer Bus Mastering. This is a method by which the NIC takes temporary control over a computer’s bus, thereby bypassing the CPU. The data would then move directly to system memory leaving the CPU free to process other tasks. This type of card is expensive, but investing in one can increase network performance by 20 to 70 percent. RAM Buffering holds data in RAM chips that are located on the NIC until it can be processed. Network traffic travels faster than most NICs can process data. Without this feature, the NIC would be a bottleneck. Some NICs have onboard microprocessors that eliminate the need of the computer’s CPU to process data, thereby improving network performance.

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Wireless Networks The term wireless network implies that it is a network that doesn’t use any cabling. This is misleading as most wireless networks utilize a system that consists of both cabling and wireless components. Wireless networks can be classified into three basic categories: •

Local Area Networks (LANs) – There are fully wireless systems, but usually the wireless components are members of a wire-based LAN.

•

Extended Local Area Networks - Wireless networks are frequently used to connect two LANs. For example, a company needs to connect two networks located in two nearby buildings.

•

Mobile Computing - Cellular and satellite technologies are increasing the popularity of wireless networking. People who are constantly on the move are able to access their networks whether they are at home, the office, or on the road.

Why Wireless? Wireless networks are useful if you need to provide a temporary network where running cabling would not be cost effective. They are also useful to create a backup system for an existing network. With some applications it is crucial that the network never goes down. A wireless system can help ensure that the network will still function even in the event of cable breaks. Mobility is another reason wireless networks are created. Doctors make rounds all over the hospital and are often not at their desks when they need to access their computers. With wireless systems, a user can access the network from anywhere in the building. Wireless is also an option for areas where installing cabling would be impossible or unsightly. This would include historical buildings where local codes would not allow renovations, or open reception areas where the cables would be visible. Outdoor installations often utilize wireless systems. Sometimes wireless systems are used to connect to remote locations such as ocean dwelling oil platforms. Wireless networks are more portable than cabled systems, making them ideal for uses that require frequent moving. Wireless networks use wireless access points (WAPs) to “connect” the network devices to each other. They function just like other access points (i.e. – hubs), but through the use of an infrared or radio medium.

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Wireless Transmission Methods There are four basic methods of wireless transmissions: •

Laser

•

Radio

•

Microwave

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Infrared

You use infrared transmissions every time you use your TV’s remote control. This involves using infrared (below Red) light to carry signals to a receiver. These signals need to be rather strong because they can be affected by light sources, such as windows. The effective distance between a transmitter and a receiver is limited to about 100 feet. Infrared is not sensitive to radio-frequency interference, and because the transmissions are tightly focused, they are also fairly immune to eavesdropping. Infrared transmits very fast because of its high bandwidths. Infrared networks typically broadcast at about 10 Mbps. Infrared Networks There are four types of infrared networks:

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Reflective Infrared

•

Line-of-Sight Infrared

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Scatter Infrared

•

Broadband Optical Telepoint

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Chapter 4 – Hardware Media and Peripherals Reflective Infrared With reflective infrared, the signal is beamed towards a central unit, which then routes the signal appropriately. Line-of-Sight Infrared With this type of infrared system, there must be a direct line-of-sight path between the transmitter and receiver. Scatter Infrared Transmission rates are slower with this type as the signal is designed to bounce off of walls, ceilings, etc. until it reaches the receiver. The effective distance of the signal is limited to about 100 feet. Broadband Optical Telepoint Broadband Optical Telepoint, as the name implies, uses broadband technology. Transmission speeds with this high-end type are competitive with cable-based systems. Radio Transmission Radio transmission wireless is popular with a high bandwidth at 10 Mbps. It does, however, require an FCC license and is subject to eavesdropping. Narrow-Band Radio Transmission This is sometimes called single-frequency radio and is similar to broadcasting from a radio station. The transmitter and receiver are tuned into the same frequency and thus it does not require line-of-sight transmission. The signal can be blocked by heavy concrete or metal walls, but unblocked it can enable mobile computing over a limited range. Spread-Spectrum Radio Transmissions Because spread-spectrum broadcasts over a range of frequencies, it is less susceptible to eavesdropping. This type of transmission is commonly used to connect multiple LAN segments together. The signals can be broadcast via two methods: hopping, or direct sequence modulation. In the hopping method, the available frequencies are divided into hops and the transmitters and receivers “hop” from frequency to frequency for a predetermined length of time. In the direct sequence modulation method, the message is broken into parts (called chips), which are then transmitted over separate frequencies.

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Network + Training & Test Preparation Guide Microwave Due to microwave transmission capabilities, mobile computing is a growing technology that provides a nearly limitless range for traveling users of this type of network. There are three forms of mobile computing: •

Packet-Radio Networking

•

Cellular Networking

•

Satellite Station Networking

Packet-Radio Networking Packets are sent via a satellite. These network-style packets are encoded with source and destination address information, and only the destination device can receive and read the packet. Cellular Networking Cellular networking is achieved via the cellular phone network. The packets sent are called Cellular Digital Packet Data (CDPD) and this form provides very fast communication. Satellite Station Networking Microwave is currently the most common of the long distance transmission methods in the US. It is used for line-of-sight communication. Terrestrial Microwave This is used for earth-based communication such as between two buildings, or across large flat open areas like bodies of water or deserts. This form of microwave communication is used to transmit over shorter distances. Satellite Microwave This is a very expensive technology and is utilized by very large corporations who pool the billions of dollars required to develop and launch a satellite. Signals are beamed up to the satellite and then sent back down to the appropriate receiver. This form of microwave communication is used to transmit globally.

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Summary The first part of this chapter covers the various aspects of network media or cables. There are three primary types of cabling: Coaxial, Twisted Pair, and Fiber-Optic. Coaxial comes in two types: Thinnet and Thicknet. Twisted Pair can be Unshielded (UTP) or Shielded (STP). Fiber-Optic cable uses pulses of light to carry signals. You should know the types of connectors used for each cable type: BNC, RJ-45, AUI, etc. In addition, you should know the maximum segment lengths for each cable type. After discussing at network cabling we then took a look at the hardware that acts as the intermediary between the cabling and the computer itself. This device is called the network interface card (NIC) and provides the physical connection to the network. It prepares, transmits, receives, and controls data flow over the network. As a network professional, it is important for you to be able to configure the network card for optimum performance. Finally, we took a look at the future. Wireless networking is the trend of the future. As a networking professional, it is important to understand the concepts associated with wireless networks. The four basic wireless types are: Infrared, Laser, Radio, and Microwave.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book. Keyword

Definition

Analog Signals AWG Bandwidth Base I/O Port Address Base Memory Address Baseband BNC Connector Broadband Buffer Cellular Networking Clocking Coaxial Cable Digital Signals DMA (Direct Memory Channel) EISA Bus Fiber-Optic Cable Full-Duplex Half-Duplex IRQ ISA Bus Laser Transmissions

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Network + Training & Test Preparation Guide Keyword MCA Bus Microwave Transmissions Narrow-Band Radio Network Adapter Card Network Interface Card PCI Bus PCMCIA Card Plenum Reflective Infrared Ring Speed RJ-11 Connector RJ-45 Connector Satellite Microwave Scatter Infrared Shielded Twisted Pair Simplex Single-Frequency Radio Spread-Spectrum Radio Terminator Terrestrial Microwave Thicknet Thinnet Transceiver Unshielded Twisted Pair 110

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Definition

Chapter 4 – Hardware Media and Peripherals Keyword

Definition

Vampire Tap

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Review Questions Chapter 4 1. What is the maximum segment length of Thinnet? 2. What is the maximum segment length of Thicknet?

3. What type of connectors are used with Coaxial cable?

4. What is the purpose of a transceiver?

5. How is a vampire tap connected?

6. What is the purpose of plenum cabling?

7. What is the maximum segment length of UTP?

8. What is the transmission speed of category 5 cabling?

9. What is the most popular of the cable types?

10. Which twisted pair cabling is less sensitive to EMI?

11. What type of connector is used with twisted pair cable?

12. What is the most expensive cable type?

13. What is the least expensive of the cable types? 112

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Chapter 4 – Hardware Media and Peripherals 14. List some advantages of fiber-optic cable.

15. What does AWG stand for and what is it?

16. Describe baseband.

17. Describe broadband.

18. What is the difference between simplex, half-duplex, and full-duplex communication?

19. What is the function of a network adapter card?

20. In Token Ring networks, what are the two ring speeds available?

21. Where would you expect to find a PCMCIA card?

22. What are some of the reasons you would need to install a wireless network?

23. What are the four basic wireless transmission types?

24. Which is the most secure type of radio wireless network?

25. Which microwave transmission type is used to transmit globally?

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Chapter 5 – Network Protocols & Standards

Chapter 5 – Network Protocols & Standards In previous chapters, we laid the groundwork for understanding networking and we looked at the different networking topologies and cabling options. This chapter explores the various protocols used in network communication. Access methods used by various network protocols will also be discussed, along with the way data is transmitted over a network in packets, or frames. Ethernet is one of the most popular networking architectures. In this chapter, we will discover how Ethernet works, as well as how Token-ring networks function. AppleTalk and ARCNet networks are also included in this chapter. After completing this chapter, you will have a working knowledge of the different network architectures and the access methods that they use. You will also understand how networks send data and what information is included in the frames that are transmitted across the network medium. You will develop an understanding of Ethernet networks and the IEEE standards for Ethernet. You will also know how Token Ring networks function and what hardware is required to make them function. AppleTalk and ARCNet architecture, while not as popular as Ethernet, are still important technologies that the networking professional needs to comprehend. A protocol is a language that computers use to communicate with other computers, in this case, over a network. In Chapter 3, you saw how each layer of the OSI Model has different protocols that define how the information travels. The way these protocols interact is called a protocol stack. The following main protocol stacks are the most important: •

Internet Protocol Suite TCP/IP

•

Novell NetWare’s Protocol Suite, IPX/SPX

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IBM’s Systems Network Architecture, SNA

•

Digital’s DECnet

•

Apple’s AppleTalk

The OSI Model was created at a later date than some of the aforementioned protocols; thus, they do not map directly to the OSI Model. Protocols function at three basic levels: •

Application protocols provide support for application-to-application interaction and data exchange.

•

Transport protocols ensure that data is sent to the correct destination without errors. Specialized Solutions, Inc.

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Network protocols route information, handle addressing, and check for errors. Network protocols also set the standard for communicating in different network environments.

A protocol must be bound to the network adapter card, also known as the network interface card (NIC), in order for it to be used with a network computer. In some instances, as in the case of TCP/IP or IPX/SPX, two protocols may be bound to one card. The order in which the operating system will use the protocol is determined by the order in which the protocols are bound to the NIC.

Access Methods In a network, multiple computers are contending with each other for access to the network media. The rules for determining how a computer may send or receive data on the network is called the access method. The access method that a system uses is designed to prevent simultaneous sending of data along the cable. If two or more computers were to send data at the same time, the data may collide and be destroyed (or partially destroyed). The access method organizes the sending and receiving of data. All computers on the network need to utilize the same access method in order to be consistent in the way that the data is handled. This will ensure that a dominant access method being used by one computer doesn’t override access to the cable causing the network to fail. There are three primary access methods: •

CSMA/CD (Carrier-Sense Multiple Access with Collision Detection) or CSMA/CA (Carrier-Sense Multiple Access with Collision Avoidance)

•

Token Passing

• Demand Priority CSMA/CD (Carrier-Sense Multiple Access with Collision Detection) CSMA/CD is known as a contention method. This is because computers on the network compete with each other for the chance to transmit data on the cable. With CSMA/CD each computer on the network checks the network cable for traffic. If it “senses” (carriersense) that the cable is free, it will send data. While there is data traveling on the cable, no computer will transmit data. Occasionally, however, two computers will transmit data at the same time and the data will collide. The Collision Detection aspect of CSMA/CD causes the two computers to stop transmitting and then attempt to retransmit after a specified period of time. Naturally, the more users who are connected to a network, the denser network traffic becomes. Greater network traffic can dramatically slow down the CSMA/CD access method.

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Chapter 5 – Network Protocols & Standards CSMA/CA (Carrier-Sense Multiple Access with Collision Avoidance) This access method is not as popular as CSMA/CD because the sending computer will transmit its intent to transmit before sending out data. Sending out messages that it is about to transmit increases network traffic and slows down network performance. It is, however, the access method that works best with wireless connections; since the wireless channel can be verified before the data is sent. Token Passing The token passing access method is used on networks that utilize the ring topology. A token (a special type of packet) is circulated around the ring from computer to computer. If a computer needs to transmit data on the network, it must wait until it possesses the token. A computer that is waiting to transmit will take control of a free token. It will add additional header and trailer information to the token as well as the data that it wishes to transmit. Data is transmitted in frames. The header information that is added to the token includes sending and receiving addressing information. The trailer includes error control information. When the computer is ready, the token is released back out onto the network and continues around the ring until it reaches the destination computer. The destination computer grabs the token and receives the data. It then adds some data to the token indicating that it received the data and releases the token back out onto the ring. The token continues around the ring until it arrives back at the source computer. The source computer takes the token and confirms that the data it transmitted was received. It then creates a new “free” token and releases it back out on the network to be used by any computer that needs to transmit. If either the source (sending) or destination (receiving) computer detect errors in the data that was transmitted, the frame would be resent. A computer in a Token Ring network must possess a token in order to transmit. Because only one computer at a time may transmit, this is not a contention method and there are no data collisions. (Some more recent versions of the Token Ring network have the capability to pass two tokens around the ring.) Demand Priority The demand priority access method is designed for the 100 Mbps Ethernet standard 100VG-AnyLAN. It has been addressed in the IEEE 802.12 standard and is based on the hubs and end-nodes being the two components that make up a 100VG-AnyLAN network. An end node in a 100VG-AnyLAN could be a computer, router, switch, or bridge. The hub manages network traffic by searching for requests to transmit from all the nodes connected to the network. The hub is responsible for verifying that all end-nodes, addresses, and links are functioning. Demand priority is more efficient than CSMA/CD because there is only traffic between the sending computer, hub, and destination computer, instead of broadcasts over the entire network. Because of the cabling method used with this access method, (four pairs Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide of wires are used, which enables quartet signaling) computers can send and receive at the same time. Contention can occur with demand priority if two computers transmit at exactly the same time, but it is possible to configure so that certain types of data receive priority when there is contention. If the hub receives two transmissions simultaneously, the one with the highest priority is serviced first. If the two transmissions have the same priority level, they are serviced at the same time by alternating between the requests.

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Chapter 5 – Network Protocols & Standards

Network Communications (Frames and Packets) As we’ve discussed previously, data needs to be processed into a form that can be transmitted across a network medium. Data files tend to be quite large, and if they were sent out onto the network medium in this form they would overload the network cabling and slow the network dramatically. Another reason for not transmitting data in such large chunks is error detection. Data is broken down into small chunks called frames or packets. (The terms frames and packets are often used interchangeably, but we will use the term packets.) Data is converted to packets in order for it to be moved across the network medium more quickly. Also, if there is a transmission error, only a small portion of the data is affected (and needs to be re-transmitted). The destination computer receives the packets and reassembles them in the correct order to translate it back into the original message. The sending computer breaks the data into packets and adds information to each packet in order to make it possible for the receiving computer to reassemble them in the correct order. This information allows for error checking after the data has been reassembled. Packet Structure Packets may contain: •

Files, information, or messages.

•

Computer control data such as service requests and commands.

•

Session control codes to indicate the need of a retransmission.

All packets contain: •

The source address of the sending computer.

•

Instructions for the network indicating how to transmit the data.

•

Instructions that tell the receiving computer how to reassemble the data.

•

The data to be transmitted.

•

The destination address of the receiving computer.

•

Error checking information such as Cyclic Redundancy Check (CRC) information.

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Network + Training & Test Preparation Guide Packet Components Headers Headers are attached to each packet. The header contains information such as an alert signal to announce that a packet is being transmitted, the source and destination addresses, and clocking information. Data This part of the packet contains the actual data that is to be transmitted. Depending upon the network, packets can be various sizes, usually from 512 bytes to 4Kilobytes. Most files are much larger than this so many packets will be made up to complete the transmission. Trailer The information in the trailer can vary depending upon the communication method or protocol used in a network. Usually, the trailer contains the error checking information. CRC (Cyclic Redundancy Check) is a mathematical calculation that is calculated at the source computer and attached to the packet. When the packets are reassembled at the destination computer, the calculation is run again. If the results are the same, the computer assumes that the packets all arrived intact. If there is a discrepancy, the CRC asks the source computer to retransmit.

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Network Standards Network standards can best be described as the physical and functional characteristic of a network. Protocols that are used with the OSI model define the rules of communication. The standards define the means of communications. For example, in a railroad, data (in this case passengers and freight) is moved in various cars. There are rules or protocols that govern how the cars are loaded and the origination and destination points. However, it is the rails and switches that govern the actual movement of the trains (data). These provide the standards for the railroads. Not all railroads are the same (some are electric, some are diesel, some are wide gauge, and some are narrow gauge), but all railroads that are built to the same standards can exchange cars (data). In this section, we are going to look at different standards for networks. Standards work in the Physical and Data Link layers of the OSI model. Logical Link Control (802.2) The Logical Link Control layer, as addressed previously, is one of two sublayers of the Data-Link layer and is concerned with managing traffic over the physical medium. The LLC has the ability to track acknowledgements, but its primary function is maintaining the network link by identifying a line protocol, like NetBIOS (Windows) or NetWare (Novell). Ethernet (802.3) Ethernet is a non-propriety network architecture that was originally developed at the Xerox Palo Alto Research Center (PARC) by Robert Metcalfe and David Boggs. The original version was a 2.94 Mbps network system that would connect over 100 computers on a one-kilometer cable. Ethernet is defined in the IEEE 802.3 standard and is a method for computers and data systems to connect over shared cabling. Ethernet uses a bus or star topology (10BaseT and 100BaseT use the star topology and 10Base2 and 10Base5 use a bus topology), and typically transmits at 10 Mbps. It is a baseband system and utilizes the CSMA/CD access method. It is probably the most popular network architecture used today. It can be installed with Thinnet coaxial (10Base2), Thicknet coaxial (10Base5), or Twisted Pair cable (10BaseT and 100BaseT). There are a number of Ethernet IEEE standards. The following are the four that transmit at 10 Mbps:

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10BaseT

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10Base2

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10Base5

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10BaseFL

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Chapter 5 – Network Protocols & Standards 10BaseT (Twisted Pair) The “10” in 10BaseT indicates that it transmits at 10 Mbps. The “Base” indicates that it uses Baseband technology (single channel). And the “T” indicates that it uses Twisted Pair cabling. While 10BaseT can and does work with STP cabling, it is most commonly created with UTP cable. 10BaseT has a maximum segment length of 100 meters (Twisted Pair wiring maximum segment length) and it is connected using RJ-45 connectors. If the segment must exceed this limitation, repeaters can be used for longer distances. The maximum number of nodes per network is 1024 and the minimum distance between nodes is 2.5 meters. 10BaseT uses the star topology. 10Base2 (Thinnet) 10Base2 uses Thinnet (coaxial) cable with BNC connectors in a Bus topology. As its name implies, it transmits at 10 Mbps using baseband technology. The “2” stands for 2 times 100 meters, indicating its maximum segment length. The actual maximum segment length, however, is 185 meters. The maximum number of nodes per segment is 30. The maximum number of segments containing nodes per network is 3. (There may be five segments but only three may be populated.) This is referred to as the “5-4-3 Rule”. The maximum number of nodes per network 90. The minimum distance between nodes is .5 meters. 10Base5 (Thicknet) 10Base5 uses Thicknet (coaxial) cable, BNC connectors and a transceiver. It transmits at 10 Mbps using baseband technology in a bus topology. The “5” stands for 5 times 100 meters, meaning 10Base5 has a maximum segment length of 500 meters. The maximum number of nodes per segment is 100 in a 10Base5 system, and the maximum number of segments is 5 with 3 being populated. The maximum number of nodes per network 100. The minimum distance between nodes is 2.5 meters. 10BaseFL (Fiber Optic) 10BaseFL is the specification for running Ethernet over fiber-optic cable. It transmits at 10 Mbps using baseband technology. The main use for this specification is for long cable runs. The maximum segment length for 10BaseFL is 2000 meters. 100 Mbps IEEE Ethernet Standards The IEEE committee has introduced new specifications for 100 Mbps Ethernet standards that can meet the demands of today’s high-bandwidth applications. These applications include video, document and image storage, and computer aided design, to name a few. The two Ethernet standards for 100 Mbps are: •

100BaseVG-AnyLAN Ethernet Specialized Solutions, Inc.

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100BaseX Ethernet (Fast Ethernet)

100VG-AnyLAN In 100VG-AnyLAN the VG stands for Voice Grade. It is known by at least four names: 100VG-AnyLAN, 100BaseVG, VG, and AnyLAN. When you see any of these terms, they are referring to the same thing. The IEEE specification 802.12 is the standard that defines this technology. It is basically a way of transmitting Ethernet frames and Token Ring packets. This uses a star topology over fiber-optic and Category 4 and 5 twisted pair cable at a data transmission rate of 100 Mbps. It can support the demand priority access method as well as an option for filtering address frames at the hub for added privacy. 100BaseVG requires its own hub and cards, and the longest cable length is 250 meters. (It can be extended longer but it requires special equipment.) 100BaseX (“Fast Ethernet”) Fast Ethernet (as 100BaseX is sometimes called) is simply an extension to the existing Ethernet 10Base Ethernet standard. It uses Category 5 twisted pair cable or fiber-optic cable in a Star Bus topology, using the CSMA/CD access method. There are three different specifications: 100BaseT4 (this uses UTP four-pair Category 5) 100BaseTX (this uses UTP or STP two-pair Category 5) 100BaseFX (this uses two-strand fiber-optic) As you know, the 100 means that it transmits at 100 Mbps and the Base means it uses baseband technology. The T4 means that it uses four-pair twisted pair cable, the TX means it uses two-pair twisted pair cable, and the FX means fiber-optic cable is used. Gigabit Ethernet Gigabit Ethernet is a transmission technology based on the Ethernet frame format and protocol used in local area networks (LANs), and provides a data rate of 1 billion bits per second (one gigabit). Gigabit Ethernet is currently being used as the backbone in many larger networks. Because of its intense speed, Gigabit Ethernet is carried primarily on fiber optic cable, although copper can be used with much shorter distances. ATM competes, to some degree, with Gigabit Ethernet, but that will be referred to later in this book. 10-Gigabit Ethernet is also on the horizon.

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Chapter 5 – Network Protocols & Standards Other Ethernet Considerations Many communication protocols are compatible with Ethernet including TCP/IP. It is also compatible with operating systems such as: •

Microsoft Windows 2000

•

Microsoft Windows NT Server

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Microsoft Windows NT Workstation

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Microsoft Windows 95 and Windows 98

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Microsoft Windows for Workgroups

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Microsoft LAN Manager

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IBM LAN Server

•

AppleShare

•

Novell NetWare

Ethernet networks may be segmented in order to improve performance, by joining with either a router or a bridge. Ethernet also works in the UNIX environment.

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Network + Training & Test Preparation Guide Token Ring (802.5) The Token Ring architecture is defined in the IEEE 802.5 standard. IBM introduced Token Ring around 1984. It is not as popular as Ethernet, but is still used today, primarily in IBM mini and mainframe systems. The Token Ring access method, more than the cable design, is what sets Token Ring apart. The name Token Ring implies that the physical layout is that of a ring. Actually, it is a star ring with each node connected to a central hub. The physical ring is in the hub and the logical ring represents the data’s path between the nodes. The cable used is STP and UTP (IBM types 1, 2, and 3), and it has a transmission speed of 4 or 16 Mbps. Like Ethernet, it uses the baseband technology. How it Works Basically, the network creates a token when the first computer comes online. The token is actually a stream of data that allows a computer to transmit data on the cable. This token will travel around the ring until a computer signals that it needs to send data. Each computer on the network acts as a repeater and regenerates the signal as the token/data frame passes through it. A computer cannot transmit data in a Token Ring environment unless it possesses the token. Data collisions are avoided because only one computer is transmitting at a time and no other computer is allowed to transmit unless it possesses the token (which won’t be released until the previous computer is finished). The computer that wants to transmit takes possession of the token. While the token is in use by a computer to send data, it is known as a data frame. The data frame is a different type of frame than the token. This is so that no other network computer will try to possess it to transmit data. The sending computer encodes the data frame with information such as: Start Delimiter This marks the start of the frame. Access Control This sets the frame priority and is also where it is encoded to let the network computers know whether the frame is a token or a data frame. Frame Control The information here determines whether the frame is being transmitted to all computers on the network or one specific “end station” computer. Destination Address This is the address of the receiving computer.

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Chapter 5 – Network Protocols & Standards Source Address This is the address of the sending computer. Message This is the data or file to be transmitted. Cyclic Redundancy Check (CRC) This is information for error detection. After encoding the data frame, the sending computer releases it out onto the network where it travels around the ring until it reaches the destination address. Note: Data travels in only one direction on a Token Ring network. Whether it travels clockwise or counter-clockwise is a matter of convention. The IEEE 802.5 standards say it travels clockwise, while IBM says counter-clockwise. The receiving computer copies the data into its buffer. It then encodes the frame with information indicating that it received the data and there were no errors detected. Or, if there were errors, it would indicate that the data needed to be retransmitted. The frame is then released back out onto the cable where it travels back to the sending computer. Assuming that the frame acknowledges that the transmission was successful, the old frame is removed and the computer creates a new token and releases it back out onto the ring. Beaconing In a Token Ring environment, the first computer to come online is assigned to monitor network activity. This computer, called the active monitor, has the responsibility of making sure that frames are being sent and received accurately. The active monitor investigates any frames that have traveled the ring more than once and ensures that only one token is traveling the ring at any one time. To accomplish this task, the active monitor performs a process known as beaconing. Every seven seconds the active monitor will send out a beacon. The beacon is passed from node to node around the ring. If a computer doesn’t receive a beacon when expected, it will notify the monitor that it didn’t receive an expected signal. This signal contains the address of its upstream neighbor, as well as its own address. The network will then attempt to diagnose and repair the problem without disrupting the entire network. As each new computer comes online, the Token Ring network initializes it so that it may join the ring. Its address is checked to confirm that there are no duplicate addresses on the network and the other computers on the ring are notified of the new computer’s active status.

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Network + Training & Test Preparation Guide Multistation Access Unit (The Hub) The actual ring in a Token Ring network is in the hub. This hub is known by a few names, such as: •

MAU (Multistation Access Unit)

•

MSAU (Multistation Access Unit)

•

SMAU (Smart Multistation Access Unit)

A Token Ring network can be expanded to have as many as 33 hubs. Each node is connected to the hub via a cable, just as in other networks that use a hub. When a computer is connected, the internal ring converts to an external ring at each connection point. MAUs can sense when one of the connected computers fails. The faulty node is then disconnected from the ring so as not to affect the rest of the network. In a pure token passing environment, the failure of one computer will bring down the rest of the network. Token Ring Cabling STP or UTP is used to connect each node to the hub. Most Token Ring networks use IBM Type 3 UTP cabling, but types 1 and 2 may also be used. Type 1 has a maximum distance from the computer to the hub of 101 meters. Using STP, the maximum distance from the computer to the hub is 100 meters. Using UTP, it is only about 45 meters. The minimum distance using either STP or UTP is 2.5 meters. There is some contention as to the maximum distance from the computer to the hub using Type 3 cable. IBM states that it is only 46 meters, but some vendors state that it is as much as 152 meters. The maximum distance between two MAUs is 152 meters. Using STP, each ring can connect up to 260 computers. Using UTP, each ring can connect up to 72 computers. Token Ring Connectors Token Ring networks use MIC (Media Interface Connectors) connectors for Type 1 and Type 2 cable. This is known as a hermaphroditic connector, as there are no male and female ends. Instead the connectors can be flipped over to connect to one another. Type 3 cable is connected with RJ-45 (8-pin) connectors if using four-pair or RJ-11 (4-pin) if using two-pair. Media filters convert cable connectors between the adapter card and the telephone jack (RJ-45/RJ-11) and reduce line noise. Using the RJ connectors allows for one cable run to connect both data and telephone equipment. Token Ring Patch Cables IBM Type 6 cable is used for patch cables in a Token Ring network. These patch cables extend the connection between the computer and the hub or between two hubs. The Type 128

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Chapter 5 – Network Protocols & Standards 6 cable has a maximum distance of 46 meters between the computer and the hub. Type 6 may also be used to increase the length of Type 3 cable or for connecting computers directly to the hub. Patch panels are used to organize patch cables. Token Ring Fiber-Optic Using fiber-optic cabling in a Token Ring network can increase the range up to ten times that of copper. Token ring networks are well suited to fiber-optic cable. Token Ring Repeaters Just as in other network environments, Token ring cable lengths may be increased by using repeaters. Using a pair of repeaters, hubs may be up to 730 meters apart with Type 1 or Type 2 cable and up to 365 meters apart using Type 3 cable. Token Ring Adapter Cards A Token Ring has two transmission speeds: 4 Mbps and 16 Mbps. The 16 Mbps card allows for a larger frame length, thereby decreasing the number of transmissions needed for data transfers. All cards on the network need to be set at the same speed. A 16 Mbps card can slow to 4 Mbps, but a 4 Mbps card cannot speed up to 16 Mbps. Therefore, care must be taken that all cards on the network are compatible.

AppleTalk AppleTalk is the network architecture used in a Macintosh environment. Although it is not nearly as popular as the Ethernet or Token Ring architectures, it is still an environment that you may be dealing with as a networking professional. AppleTalk is included with the Macintosh operating system software; therefore network capabilities are built into all Macintosh computers. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide AppleTalk networks are usually called LocalTalk. When a computer goes online in a LocalTalk network, the device assigns itself an address. This address is chosen at random from a range of available addresses. It will then broadcast the chosen address to determine if any other computer online is using the address. If it is not being used by another computer, it will store it to use each time it goes online. Apple has always been open to third-party development. As such, AppleTalk can be used by non-Macintosh computers such as IBM compatible computers, mainframe computers, Digital Equipment Corporation’s VAX™ computers, and even some UNIX computers. LocalTalk LocalTalk uses STP, UTP, or Fiber-Optic cable in a Bus topology. It uses the CSMA/CD access method and can connect a maximum of 32 devices. Since Macintosh builds-in the hardware for LocalTalk in every computer, it is very inexpensive to initiate. LocalTalk performance is rather limited, so it is not used as often as Ethernet or Token Ring. AppleShare The file server on an AppleTalk network is called AppleShare. AppleShare also provides a print server. The client software for AppleShare is also included in the Apple operating system. Zones LocalTalk networks may be joined together using zones. A zone is a named Subnetwork that users may access simply by selecting it. This is useful for expanding the LocalTalk network or for relieving traffic on a larger network. AppleTalk can incorporate other types of networks such as Token Rings, by using zones. EtherTalk EtherTalk is simply a way to run AppleTalk on coaxial cable using an EtherTalk NB NIC. EtherTalk may be implemented on Thinnet or Thicknet coaxial cable. TokenTalk TokenTalk is simply a way to run AppleTalk in a Token Ring (IEEE 802.5 Standard) environment. The TokenTalk NB card is used to attach to a Token Ring network.

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Chapter 5 – Network Protocols & Standards

ARCNet ( Attached Resource Computer Network) In 1977 Datapoint Corporation developed the ARCNet technology. It is a simple and inexpensive network architecture that may use a Bus or Star Bus topology. ARCNet was developed before the IEEE 802 specifications, but it can be adequately charted to the 802.4 standards (Token Bus LAN). It uses a token-passing access method that transmits at 2.5 Mbps. A later version, called ARCNet Plus, has a data transmission rate of 20 Mbps. Just like other token-passing access method architectures, a token is needed in order for a computer to transmit data. Instead of the token traveling around a ring, the token is passed in numerical order. If computer #1 is at one end of the network and Computer #2 is at the other, the token still passes in numerical order. Obviously, this can really slow a network down if the computers are not in order. ARCNet transmits data in packets. These packets contain the destination address, the source address and up to 508 bytes of data. The ARCNet Plus architecture can hold up to 4096 bytes of data. ARCNet utilizes hubs. These hubs may be passive, active, or smart. ARCNet can use twisted-pair or fiber-optic cabling, but is normally installed using RG-62 A/U coaxial cable. If using an active hub in a Star topology, with coaxial cable and BNC connectors, the maximum cable distance between the computer and the hub is 610 meters. This distance drops to only 305 meters if using the Bus topology. If using either the Star or Bus topology with UTP and RJ-45 or RJ-11 connectors, the maximum cable distance is 244 meters.

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Network + Training & Test Preparation Guide Wireless (802.11) IEEE 802.11 is the latest generation of enterprise-class wireless LAN technology. Speeds up to 54 Mbps will be available within wireless networks (LANs to be more specific). Interference can be lessened by their ability to function in their own band (in the GHz range, generally). The capacity to use wireless technology is there for large-scale deployments as well. Wireless technology is discussed in further detail in chapter four.

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Chapter 5 – Network Protocols & Standards

Summary This has been another information intensive chapter and we covered a lot of information on the different networking architectures. Managing network data is all about traffic control, and the access method (such as CSMA/CD, CSMA/CA, Token Passing and Demand Priority) is the governor of how traffic is controlled on a network. It is important for the networking professional to understand the characteristics of each access method. Data is sent out on the network in smaller chunks of data called packets (or frames). If it were sent out in one continuous stream it would quickly bring network traffic to a halt due to the large size of the data. Packets will include information to identify the source address, destination address and the actual data that is being transmitted. Most packets also include error checking or CRC (Cyclical Redundancy Check) methods to check the reliability of the packets received. Packets consist of three components: the Header, which includes an alert signal that a computer is transmitting, the source and destination addresses, and clocking information; the Data; and the Trailer, which is where the error checking calculation is located. The popular Ethernet architecture is defined in the IEEE 802.3 standards. As a networking professional you will encounter this type of network most often. Therefore, it is important that you are knowledgeable about the different types of Ethernet such as 10Base2, 10Base5, and 10BaseT. The 100 Mbps and Gigabit Ethernet architectures will be even more prevalent in the future. It is extremely important that you understand the different cabling schemes and their connectors as well as the maximum segment lengths for all of these different architectures. Although Token Ring is not as popular as Ethernet, it is still a common architecture and is said to be increasing its market share by as much as 20% per year. Be sure that you understand how this architecture works, as well as the different cabling schemes and cable distances, etc. AppleTalk and ARCNet architectures may be used less than Ethernet or Token Ring, but as a networking professional you will encounter them. It is important that you understand their specifications and access methods as well. Be sure to complete the following exercises and review questions. If you are having trouble with any of these concepts, go back and review the chapter again.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword Access Method AppleShare AppleTalk ARCNet Beaconing CRC CSMA/CA CSMA/CD Demand Priority Ethernet EtherTalk Frames Header Hub LocalTalk Multistation Access Unit Packets Patch Cable Smart Multistation Access Unit Token Passing

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Definition

Chapter 5 – Network Protocols & Standards Keyword

Definition

Token Ring TokenTalk Trailer Zones

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Review Questions Chapter 5 1. What are the three primary access methods? 2. Describe the difference between the two different contention methods, CSMA/CD and CSMA/CA.

3. Why isn’t token passing considered a contention method?

4. Describe how data is transmitted in the Token Ring architecture.

5. What happens if two computers using the demand priority access method transmit at exactly the same time?

6. How is data transmitted over the network cable?

7. What is CRC and what part of the packet is it usually located in?

8. What sort of information do packet headers contain?

9. What does the “T” in 10BaseT indicate?

10. What is the maximum segment length in 10Base2?

11. What type of connectors are used in 10Base5?

12. What type of cable is used in 10BaseFL?

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Chapter 5 – Network Protocols & Standards 13. Name the two main 100 Mbps Ethernet Standards.

14. Which IEEE Specification defines Ethernet?

15. Which IEEE Specification defines Token Ring?

16. What are the two transmission speeds of Token Ring?

17. How are data collisions avoided in the Token Ring architecture?

18. Describe beaconing as it applies to Token Ring architecture.

19. Which way does data travel in a Token Ring network?

20. What is a SMAU?

21. Describe a MIC connector.

22. How does a computer on a LocalTalk network obtain its address?

23. What is the purpose of AppleShare?

24. What type of access method does an ARCNet network utilize?

25. How does data flow in an ARCNet network?

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Chapter 6 – Network Design

Chapter 6 – Network Design In this chapter we are going to put to use many of the terms and concepts that we studied in earlier chapters of this training guide. We will start by looking at what it takes to layout a network from scratch. Then we will study in more detail network adapter cards, how they are installed and how to troubleshoot them. Finally, we will consider hardware compatibility. Hardware compatibility is a major consideration in network design and is often the source of troubles when expanding or upgrading networks.

Starting a Network Project A unique opportunity for any network professional is to design a network from beginning to end. For most of us this will be a rare event since most companies already have a network and are working with expanding or increasing the performance of what they already have. The most important aspect of creating a new network is to document everything that you do. This is especially true if you will be maintaining or upgrading this network in the future. (If not, whoever is assigned the upgrade project will be forever indebted to you. The place to start a new network is with a pad of paper and a pencil or two. Even if this network is your own, rather than a client’s, you need to approach the project as if it were for someone else. This will give you the discipline to ask yourself the right questions and to begin the process of documentation. There are two things that you will need to know. The Customer Obtaining a clear understanding of your customer and their needs is essential when designing a network. As a network professional, you will have a lot of knowledge and expertise with networks. This is well and good if you are designing a network for your own use. However, in many cases, you are not designing for yourself. You could design the best high-speed low-cost Windows system that was ever imagined, but if your customer is a Macintosh user, your design will not work for them. The following is some suggested information that you should gather about your customer: The basics – name, address, etc. (demographics). The size of the company and the portion of the network affected. The product – this is very important as a graphic arts client will have different needs than an engineering firm or a law office. The facility – how big is the building(s) and what is the layout of the various offices? Current level of technology – how many computers do they have, who has them, are there any printers or scanners, etc? If, for example, this is a Macintosh-based company, you certainly don’t want to design a network around Windows. Most importantly, pay attention to details. The customer’s likes, dislikes, and goals. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide The Network Goals In addition to the customer’s needs, you must get a clear definition of goals of the network. The following are some questions to consider: Will this be a simple LAN or a complex WAN with Internet and remote users? What are the future needs? Is this network to start small and expand later, or will it meet the requirements of the latest technology? How much traffic do you anticipate now and in the future? A business office moving 1000 documents and spreadsheets across a network will generate far less traffic than a graphic arts or engineering office moving 1000 large imaging files. For example, a textonly MS Word file will be approximately 30 KB of data while a single page image file will average 50 KB, if the file is compressed, or as much as 8 MB for the same image scanned (black and white) at 300 dpi uncompressed (even more if color or grayscale). So, the same 1000 documents could be as little as 30 MB, or as large as 8 GB. Is an Internet connection needed now or in the future? Will it be for all users or just a select few? What additional services will the network need to provide? Sharing of resources, files services, print services, etc. Once you collect this information, prepare a design document. Your document should include a summary of all the information you collected. This can be done using any word processor or spreadsheet program. You may want to consider using a drawing program to create a layout of the facility. This can be a simple program like Microsoft Paint, or as complex and as expensive as AutoCAD. There are many intermediate drawing packages that are available. A good intermediate program is Visio 2002. This program provides simple templates for both facilities and network components. Remember, at this time, you are not documenting your network, only documenting the facility and the requirements of the network. You will need this information as you make decisions in the next few steps. With this information in hand, you are now ready to begin the designing of the network.

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Determine Network Type Once you collect all the information described above, you will need to start making some decisions. The first is the type of network you will be designing. Here you will have two choices: peer-to-peer or client/server. The decision that you make at this time will have an affect on the hardware and software choices that you make in the future. You will need to take careful consideration of the information collected in the first step to assist you with this decision. The following lists the information that you will need in order to choose your network type. If you do not have this information go back and get it. The wrong choice now, may cause problems in the future. The number of nodes (computers and other resources) on the network. The level of security required. This can range from none to very high. Also, not all nodes may need the same level of security. The type of business and how that will affect network traffic. Skill level of the network users. Are they able to handle a sophisticated network or must the network be transparent to them? The available budget (both now and in the future). The commitment of management and users. Are they committed to the change or are they going to resist the change? When to Choose Peer-to-Peer There are many reasons why you would want to choose peer-to-peer. The most prominent are simplicity and cost. In a peer-to-peer network, all computers are equal. They can provide services to the network and use services provided by others. For example, if you have a printer connected to your computer, you can share it to the network and anyone who has access to the network can send work to it. Likewise, if a colleague has a color printer and you don’t, you can send work to it if you need color printing (assuming that they share the printer to the network). Peer-to-peer networks are economical to setup and implement. First, they do not require a high-power computer with lots of speed and processing power. Most personal computers today will have more than enough power to successfully operate in a peer-to-peer environment. You may have to add network cards and cabling, but most operating systems like Windows 95 and up and Macintosh OS X are “network ready.” That is, they include the necessary software and protocols for file and print sharing. You may need to install the software, as generally it is not installed during a standard installation. As long as you have the original software disk (CD), you will have no problem. Keep in mind that you may not be able to mix two different operating systems without additional software or upgrading to a client/server network. The disadvantages of peer-to-peer networks are security and limited network size. Peerto-peer networks do provide some security in the form of allowing you to select what you want to share to the network. This sharing is on a directory level. This means that every 142

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Chapter 6 – Network Design file in the directory will be available to the network. As for size, the general rule is that peer-to-peer networks should be limited to about 10 workstations. You can connect more workstations, but there will most likely be reductions in network performance as stations are added. In a peer-to-peer situation, if anyone is using a resource on your workstation, such as your printer, they will also be using your processor to do their printing. The result will be a slow-down of performance on your workstation. This will be especially true if your workstation is using an older, slower processor and/or has limited memory (RAM). In a small network where everybody knows each other and security is not an issue, a peer-to-peer network may be the perfect solution. Also, a client with a limited budget may consider this type of network as a starting point or entry-level network. When to Choose Client/Server On a client/server network (also known as server-based networks), all network resources are usually centralized. This means that one or more computers are designated as servers and provide the resources for the entire network. Since these computers are larger, have high-power processor, and lots of memory, the performance of the network will be better than in a peer-to-peer network. Another advantage of server-based networks is that the servers are never turned off. This means that if you need to use the color printer that is connected to the print server, you will not need to worry if Mary is on vacation and her computer is turned off (since she is the only one in the company that has a color printer). Using a file server to maintain all of the company-wide files, instead of backing up individual workstations, is another advantage of a server-based network. This centralized file system also makes for easy transfers of files throughout the company, 24-hours per day. Also, if employees need remote access, information can be made available to them through a RAS (Remote Access Server) connection. Perhaps the most significant aspect of using server-based networks is security. These server-based networks provide a central database that manages access to all the resources as well as the network itself. Before you can use any resource, you must have both the authorization to use the network and permission to use the resource. In a strict peer-topeer network, any user can log on to a workstation (with a new name and password) and gain access to the network. In a server-based network, only a network administrator can create a user name and assign permissions to that user. Last but not least, server-based networks are scaleable. This means that you can start small with one server and a few workstations, and expand as your needs expand. While there are many advantages, you will also need to consider the disadvantages. The most prominent disadvantage is the cost to install and operate the network. It is obvious that server-based networks will require better and higher-powered hardware, but what is often overlooked is the cost to administer the network. The more sophisticated the network, the more knowledgeable the administrator needs to be. Most employees have little or no knowledge of the workings of computers, must less the workings of a network. For these people, the network must operate transparent to them. In small networks, all that is needed is one or two knowledgeable people to act as administrators. Remember, this will take part of their normal workday will be taken up to react to any problems and maintain existing accounts, etc. In large networks, administration can be a Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide full-time job for one or more people and may even require the skills of a certified network professional. Each network operating system supplier has their own certification program such as Microsoft’s MCSE (Microsoft Certified System Engineer) and Novell’s CNE (Certified Novell Engineer). Making the Choice Making that final decision is often difficult. In some cases, the answer will be very obvious; in others it could go either way. When you are sitting on the fence, be sure to follow a disciplined procedure: Collect all your information. If you are not sure you have enough information, get more. Prepare a case (on paper) of the pros and cons of each. If all else fails, present each case to the client and let them make the final decision. Once you have made this decision, stick with it and move forward. This decision will be the basis for the rest of your network design. Public and Private networks In addition, let us define the difference between the terms public and private network, since your organization will more than likely need access to the Internet and networks outside of their LAN. A private network would be a corporate network or an Intranet, which would limit its access to those outside of the company. A public network would be the Internet, with open access to the global community. Actually, you can use any address that you want to use inside of your own network and behind your firewalls. The only problem is that if your firewall were to come down, then you might have an address conflict with another entity on the Internet. For this reason, there are specific addresses that are filtered by the routers at the backbone of the Internet. The use of these addresses will completely prevent the address conflict issue. For this reason, it is highly recommended that you use these addresses for your private addressing.

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10.0.0.0 -10.255.255.255

255.0.0.0

172.16.0.0 -172.32.0.0

255.255.0.0

192.168.0.0 - 192.168.255.255

255.255.255.0

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Network + Training & Test Preparation Guide Define the Starting Place If you are designing a network from the ground up and literally starting with a blank piece of paper, you can skip this section. On the other hand, if all or part of a network already exists, you will need to make a detailed inventory of the materials you already have. You may also want to take an inventory as part of your initial evaluation. The documenting of existing equipment includes two components: hardware and software. When taking this inventory, whether hardware or software, don’t just simply ask someone what he or she has, ask him or her to show you. Remember, this is a detailed inventory that requires someone that is knowledgeable in computers and networks. That person is you! Be sure to take a small toolkit and a flashlight with you. Some of the information you need may be inside the machine and you will have to remove a case or two. The best approach is to make an inventory sheet for each piece of equipment. This form should identify the equipment and its specifications. The following page shows an example of what an inventory sheet might look like. Use it as a starting place to build your own. Also, if you are creating a new network and have no inventory to work with, you must add new hardware, use this sheet to define your proposed new equipment. The following is an example of an inventory sheet. Feel free to use this as a starting place for developing your own customized form.

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Network Equipment Inventory Sheet Item Number: ___________ Type of Equipment:

† Computer † Printer † Telecommunication † Other If Other: _______________________________________

Location: Identification:

Computer:

Printer:

Peripheral:

Make:

____________________________

Model:

____________________________

Serial #:

_____________________________

Processor (Type and Speed)

____________________

RAM

____________________

Hard Drive(s)

____________________

Monitor

____________________

Video Card

____________________

Modem

____________________

Connected Peripherals

____________________

Bus Type (ISA, PCI, etc.)

____________________

# of Free Slots

____________________

Network Card

____________________

Installed RAM

____________________

Interface (Parallel or SCSI)

____________________

Network Compliant (Yes/No)

____________________

Type of Device

____________________

Interface (Parallel or SCSI)

____________________

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Describe the device and its function.

Software:

If this device uses software, describe each program. Name of Program:(Operating System) __________________

Version Number:

____________________

Licensing Information:

____________________ ____________________

Original Disk (CD) Available:

____________________

Name of Program:

____________________

Version Number:

____________________

Licensing Information:

____________________ ____________________

Original Disk (CD) Available:

____________________

Name of Program:

____________________

Version Number:

____________________

Licensing Information:

____________________ ____________________

Original Disk (CD) Available:

____________________

Use additional paper if necessary.

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Design the Network At last we should have enough information to start designing our network. It is time to get out that pencil and paper, or the software drawing program that you used to create the layout of the facility, and collect all of the documentation you have been working on. Using the inventory sheets and the objectives of the network, make a drawing of the facility and each network node. Start with the location of existing equipment (if any) then draw the location of the new equipment. This might be a good time to start identifying each node with a name and number. By assigning them a number now, it will make future documentation easier.

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Chapter 6 – Network Design Media Selection Media selection is an aspect of installing a network that should not be taken lightly. It is the most labor-intensive of all the processes and the most costly to replace. The most important aspect of media selection is to be sure that the media you choose will meet the performance criteria of the network. For example, a small network with only a few workstations sharing files and printing will probably work fine with CAT 5 UTP cables. The 100 Mbps speed of this media will handle this workload without problems. However, if you are going to have hundreds of computers or transfer large quantities of large files, such as in an imaging environment, you will need to install CAT 5e or CAT 6 UTP to be able to take advantage of its 1000 Mbps speed. In addition, if you are not sure if expansion is in your future, it would be worthwhile to spend a little more now and install CAT 5e or CAT 6 than to replace it in 2 to 3 years. Realistically, CAT 6 is the UTP of choice. If economics are a major concern and you are designing a small temporary LAN, consider Thinnet coaxial cable. These cables are inexpensive and if all computers are in the same proximity, a simple bus topology with each computer in a series will save on the budget (don’t forget to terminate each end). Cable lengths must be considered. If you intend to use UTP or STP cables, you must make sure that the longest connection (computer to computer, or hub to computer) does not exceed 100 meters (328 feet). In most environments this will be no problem, but if this is a large facility, and the run from the server room to the maintenance shop is 400 meters (1312 feet), you will need Thicknet coaxial cables. On the high end, where money is no object and security is critical or you have long distances to cover, (up to 2 kilometers – 6562 feet) choose fiber optics. The following are several other factors that must be considered before making your final choice: Topology – If you use a physical star topology, you will need to remember that all cables must originate from the hub. Therefore, hub location is critical for determining cable lengths. Cable Grade – Local fire codes, or just good common sense, may require that you install plenum grade cables for part or all of your installation. It may be more cost effective to purchase a large quantity of plenum grade rather than a mix of plenum and standard grade. Cable Type – If your goal is to save money now and you don’t need a high-speed network, you might consider CAT 3. However, for long term use and eventual upgrade to 100 MHz, the cost of CAT 5 is not significantly more than CAT 3. It will cost a lot more to upgrade later. 5-4-3 – If your installation is coaxial Ethernet, you must comply with requirements of the 5-4-3 rule for number of segments, repeaters and nodes.

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Network + Training & Test Preparation Guide Noise – If all or part of the installation is located in an industrial environment (vibration and noise), or uses lots of electrical or electronic equipment that generates EMI (electromagnetic interference) or RFI (Radio Frequency Interference), you may need to install fiber optics at least in that area. Environment – If all or part of the network is in a hostile environment (corrosive manufacturing) you should consider alternatives like fiber optics. Fiber optics are also a good alternative when the manufacturing environment cannot allow for any possibility of even a small spark, since they don’t use electricity to transmit a signal. Environmental Concerns A major concern that is often overlooked when designing a network is the actual environment in which the computers will be operating. Like us, they are sensitive to temperature changes. Fortunately, the same conditions that are good for people are often ideal for computers. Constant temperatures of around 70° F, with a relative humidity of 30 percent, are usually what is found in the office environment where most networks are installed, and this is also the ultimate atmosphere for a computer. Variable temperatures, low-humidity, which can generate damaging ESD, high-humidity, which can cause corrosion, and fluctuating line-voltages from the incoming power source, can all cause a computer to fail or behave erratically. Less than ideal conditions will also decrease the life expectancy of your equipment. Most larger companies will have a dedicated room for their server (the Server room), which is kept at the ideal temperature for the equipment. It is not strictly necessary to have a dedicated room for the equipment, but it is important that the room be well ventilated and climate controlled. The equipment should be shielded from ESD, EMI, and RFI, and should have a method to ensure that clean power is available, such as a surge suppressor and an uninterruptible power supply. NOS Selection Choosing the network operating system is a matter of user preference. Most network operating systems today are robust and will operate transparent to the users. Therefore, on the surface, it doesn’t really matter. As long as it is configured well and meets the needs of the customer, it will work. On the other hand, sometimes the customer will make the choice for you. If the customer has always used Novell NetWare and is satisfied with the performance, it may not be prudent to recommend the change to Windows 2000/2003. Protocol Selection The most important issue with selecting a protocol is to use the same protocol throughout the network. The next choice is whether to use a routable or non-routable protocol. The non-routable protocols, such as NetBEUI are simple and work well with peer-to-peer networks and small LANs. However, if you intend to work with a larger network or WAN, which requires the use of routers, you need a routable protocol such as TCP/IP. These routable protocols are more difficult to configure, but are not limited.

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Putting it all together Installing the media is a task that is often best left to someone who specializes in cable installation. So let’s assume that you or your specialist has run all the cables. There are a few more components that need to be installed. Make sure that either you or the specialist marks each cable at both ends. This way you can identify each location. Cable to Computer Depending on the selection of cable, you will most likely need to install a wall outlet. The type of outlet will depend on the type of cable. In most cases, if using CAT 5 or CAT 6, it will be a wall plate with an RJ-45 outlet. These outlets will make for a nice and neat installation and will make the room ready to connect a computer to the network. The next step will be a patch cable that runs between the network adapter card and the outlet. One thing to remember about these patch cables is that their length must be considered as part of the overall length of the cable. One advantage of using CAT 5 or CAT 6 cable in a star topology from a hub, is that you do not have to install a computer on every outlet. The hub will know that the cable is not connected and will simply ignore it. This way, you can install future or optional locations in preparation for expanding.

Cable to Hub The connection of the cables to the hub will usually take place in the “server room.” This is a centrally located room or closet that will house the primary server and hub. All the cables will be brought to one location. To keep these organized, the cables are connected to a patch panel. This is just a strip of RG-45 connectors. Each cable is in turn connected to one of the outlets and a patch cable is then used to connect it to the hub. 154

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Network Adapter Cards Installing the cabling for a network is literally installing the Physical layer of the network. Once that is done, there is one more part of the Physical layer that must be installed. That part is the network adapter card. This card is a circuit board with all the electronic circuitry and components necessary to physically connect to the computer and the media. Because it must connect to both the computer and the media, we must select a card that is compatible with both. Therefore you must know the requirements of each. Actually, there are three things to consider: •

Network Compatibility

•

Media Compatibility

•

Computer Compatibility

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Network and Hardware Compatibility Network compatibility is a key consideration in network design. Building across-theboard compatibility for hardware and software at the design stage will simplify future maintenance and troubleshooting. Making incompatible components work together is possible in most instances, but in the long run this will add significantly to the cost and time requirements of maintenance, administration, and expansion projects. This section will look at compatibility issues. Adapter Card Compatibility A network card acts as the interface between the computer and the network. Therefore, there are compatibility issues on both sides of the interface. Card to Network Network adapter card compatibility is simple. The adapter card (NIC) must be able to communicate on the network using the same standards and protocols as the other components. If you are installing a Token Ring network, you must have Token Ring cards. An Ethernet card simply won’t work on a Token Ring network. Also, the speed of the card is important. For example, a 10 Mbps card (10BaseT) will work on a 100 Mbps network (100BaseTX), but only at 10 Mbps. Some of the newer 100BaseTX cards will work on a 10BaseT network, but only at 10 Mbps. In addition to being compatible with the network, the card must be compatible with the computer. Resolving these issues is actually quite simple, but requires some knowledge of the inside workings of a computer. The processor (CPU) in a computer will communicate with the expansion cards through the expansion bus. This bus is a group of parallel conductors that carry digital information to and from the CPU to all parts of the computer. Depending on the vintage of the computer, the number of connectors, and therefore the speed at which data can be moved, will change. Network cards are designed to meet the standards of the bus. The actual connection between the card and the bus is called an expansion slot because of the way the cards are installed. On one side of the circuit card are a group of gold “fingers” that fit into the slot to provide the electrical connection. The different types of cards are designated by the orientation and number of these connections. There are four types of cards that you will encounter (ISA, EISA, Micro Channel, and PCI). Before purchasing a network card, you will have to know the type of expansion slots used in the computer and whether or not there are any free slots. The best way to find out is to remove the case and look. Note: Laptops and proprietary computers will have special cards designed to fit their architecture. Laptops generally use PCMCIA cards, also called PC Cards. Some network cards provide diagnostic lights, which can be a useful tool. These are little LEDs (one, two, or three) that indicate the status of the card. Not all cards are the same, so you will have to check the documentation to be sure of their meaning. In general, a Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide green light indicates that a proper network connection exists and a flashing yellow light indicates that data is being transferred. Keep in mind that a green light does not mean that the computer is properly configured and you can use the network; it only means that the proper connection has been established between the card and the network. Card and Computer Installing a network adapter card is not any different than installing any other expansion card in a computer. Understanding the installation process is the key to preventing conflicts. The details of installation will vary depending on the type of computer and the operating system installed. Since describing the installation of a network adapter card for every system is beyond the scope of this training course, the following is a generic procedure that defines the key points that you must follow: Purchase the card. First ensure that it is compatible with your system (network and computer). Configure the IRQ and I/O address. In most cases with a new card, this will be done with the installation software or by the operating system. If your system is not Plug-n-Play, you may still have to manually set some jumpers or switches. If you must do this manually, be sure that no other device has already been assigned the IRQ or I/O address. If there are any conflicts, the computer may not boot or the conflicting devices might not be able to work simultaneously. Physically install the card. Remove the case and install it into a free expansion slot. Note: If you must remove the case, be sure to follow ESD (electro-static discharge) procedures. Hint: you may not want to put the case back on until you have confirmed that the card is working. Connect the network cabling. Install the appropriate drivers for the card. Drivers are usually supplied with the network card. Many operating systems already include drivers for most network cards. If you don’t have the driver or want to make sure that you have the latest driver, you can usually download them from the manufacturer’s web site. In addition, if you upgrade your operating system, you may need to download a new driver in order to make it work or to increase its performance. Now the network adapter card is installed, but you are not finished yet. You need to configure the card to work with your network software. You still need to bind the card to the network protocols that you are going to use. Finally, you will need to check the documentation for the network operating system that you are using. Note: Many computers that are designated as servers or gateways can have more than one network card installed. Each card must be configured for a different network.

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Chapter 6 – Network Design Media Compatibility Media compatibility is the ability of the cabling to physically connect to the card. In the case of UTP, the card should have an RJ-45 connector. For Thinnet or Thicknet, the card must have a coaxial BNC connector. Some STP cards require special connectors. For example, AppleTalk employs a DIN-type connector and IBM Token Ring uses a DB-9 connector. To increase marketability of their cards, some manufacturers will provide two, and possibly three, different connectors allowing for multiple installation scenarios. The bottom line is to be sure to look before you buy. Computer Compatibility Computer compatibility is often a serious problem encountered when installing a network in an existing facility. Many growing companies purchase their computers only as needed and will select the best buy of the day. While this makes good sense to the accounting department, it can create havoc when you have to connect them and actually have them communicate. You may have to connect some older “legacy” hardware with some new high-speed high-tech machines. A typical problem encountered with highly departmentalized companies is that each department has its own preferences. For example, the graphics arts department may be Macintosh-based, the engineering department may be PC-based, and the administrative department may just be thankful for having whatever they could get their hands on. These types of problems can be more personal in nature, as some individuals will not want to change their way of doing things just to have a network. If you encounter this type of situation, the decision may end up with the company’s management and you will have to work with it. However, it is your responsibility to point out the strengths and weaknesses of each scenario, as well as possible solutions.

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Preventing Compatibility Problems There are really only two methods of resolving compatibility issues; hard work and standards. Hard Work Hard work and attention to detail are your only allies when it comes to setting up a network from an existing system. Unless you are very lucky and are installing a new network, with identical computers that were purchased from the same supplier, that were identically configured, you are going to have your work cut out for you. Your only recourse is to document every computer and piece of hardware that must be connected to the network, and detail both its hardware and software. This will most likely require that you remove covers and identify components such as the modem and the network card, if installed. You will also need to know the type of processor and the type and number of available expansion slots. With this done, boot up each computer and note the operating system and any installed software. With this information in hand, and knowledge of the network operating system, you should be able to predict potential hardware compatibility problems and take action to prevent them. Standards Earlier in this training course, we learned about network protocols and standards. Standards are one way in which hardware and software suppliers can develop a product and be assured that it will work with the products of other suppliers. As long as the system is designed to meet the same standards, each component will work with the others. As the network designer or administrator, you will need to establish the standards for your network. By defining the standards to which the network must comply, you will be assured that any new additions will function properly.

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Resolving Compatibility Problems No matter how careful you are, sooner or later you will encounter compatibility problems. The networking industry is in a constant state of change and unless you want to be left behind, you will need to upgrade. Most hardware compatibility problems are resolved by installing the latest drivers. For example, when upgrading from Windows 98 to Windows XP, you find that your modem, network card and/or printer no longer work. More than likely, all you need to do is install the Windows XP drivers for the offending hardware. The first thing you need to do is determine if the original disks/CD that came with the device has the drivers to match the new operating system. If the operating system was released after you purchased the device, you probably do not have the necessary drivers. In this case, the Internet is the answer. If drivers exist, you will be able to locate and download them from the manufacturer’s web site. Also, there are several web sites that specialize in downloading drivers. Drivers for a particular device are not always available for all operating systems. You should always confirm the availability of drivers before purchasing an unknown device. Some devices do not have drivers for all operating systems. Minimum Requirements When evaluating or considering an upgrade or change of an operating system, you will need to check the manufacturer’s recommendations for the minimum requirements to operate. These are the bare minimum requirements to run the system. These requirements by no means indicate what you should purchase, only that if you don’t meet these requirements, the system will not run. Most manufacturers will also publish suggested minimum requirements. These will be somewhat higher than the required minimum and are what you need to operate the system at a normal performance rate. A good example is Windows 95. Microsoft says that you do not need a mouse to run this operating system. This is a true statement; however, have you ever tried it? You can run Windows 95 without a mouse by using only keystrokes, but your proficiency will be very low. The later Windows operating systems require a mouse as one of the minimum requirements.

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Network + Training & Test Preparation Guide The following table lists an example of the minimum requirements for three operating systems:

HCL and Windows 2000 To help alleviate compatibility issues some manufacturers provide HCLs, or hardware compatibility lists. An operating system such as Microsoft Windows 2000 is hardware dependent. It is considered an advanced operating system and will not work with all hardware. If you were to purchase an econo-version of a computer or one that is highly proprietary, it most likely will not work with Windows 2000. To assist in making an informed purchasing decision, or to confirm whether or not your existing hardware will work with Windows 2000, you will need to check the HCL for that product. This list will ship with the 2000 package (on the CD-ROM) and 2000 will make a check during installation. If you want the latest list, you can get it from one of Microsoft’s web sites. Microsoft Windows Catalog Still another web site to check for compatibility of hardware and software, especially with the newest operating systems such as Windows XP and Windows Server 2003, is the Microsoft Windows Catalog at www.microsoft.com/windows/catalog. Here you will find the latest information about hardware and software that is Designed for Windows XP and Windows Server 2003 or at least tested to be compatible with these operating systems. This is part of the Windows Logo program. You can also look for the corresponding logos on the boxes of hardware and software that you are considering purchasing for your network.

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Review Questions Chapter 6 1. What are the two tools required to initiate a network design? 2. What are the two areas of concern when starting a network project?

3. What are the two most prominent reasons to choose a peer-to-peer network?

4. What is the number one reason for choosing a client/server network?

5. Is NetBEUI a good protocol to use with a large WAN?

6. Your client is installing a small Ethernet network and trying to save money at the same time. However, he intends to expand the network in the future. Give one reason why you should recommend that he spend a little more now and install CAT 6 cabling instead of CAT 5.

7. You are expanding your network and will need to invest in 50 to 100 new network cards. Your accounting office found a really good deal on network cards, but they are not all the same. Why should you refuse this offer?

8. Your company just bought ten new computers and all are guaranteed to meet the minimum requirements of Windows XP. Was this a good purchase?

9. How do you know if a new piece of hardware will work with Windows XP?

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Chapter 7 - Expanding a Network No matter how well you design a network, sooner or later, it may be too small. This chapter will discuss several techniques for expanding a network.

Expanding a LAN with Hubs A common method for expanding networks is to use a hub. A hub is a device that acts like the central station for all computers on the network. There are several different types of hubs, from simple five-connector hubs used to connect five devices, to larger hubs that can connect many more computers. For example, you cannot use an Ethernet hub on a Token Ring network. In addition to being called “hubs,” you may also hear them referred to as: •

Concentrators

•

MAU or MSAU– Multistation Access Unit (Token Ring)

•

Patch Panel

•

SMAU – a Smart MAU

Hubs can be either active or passive. An active hub will require power and will often provide some form of signal conditioning (amplifies weak signals). Active hubs can be used to extend the length of network cabling by connecting them in a series. Passive hubs do not use external power and are used only to concentrate the cables in a common location.

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When a LAN is Too Small There are several reasons to consider expanding a LAN: •

Too much network traffic.

•

Long waits to access a printer or file.

•

Traffic-generating applications, such as databases, have increased response times.

•

You are just plain tired of your old system and want to get your system updated.

When the time comes to make a serious expansion to a LAN, the simple hub just won’t do the job. Depending on the objectives of the LAN, you will have to employ one or more different pieces of hardware. Fortunately, there are several other devices that can be used to expand a network. Each has its own unique advantages and disadvantages. Repeaters A repeater is a device that is used to extend the cable length on a network. They do not translate or filter any information. They do however, amplify the signal, thereby compensating for signal loss due to long cable lengths. Repeaters work in the Physical Layer of the OSI model.

Bridges A bridge does the same things as a repeater, but has one additional feature. A bridge can be used to isolate segments on a LAN, thus reducing the traffic for each segment. Bridges work in the Data Link Layer of the OSI model. 166

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Routers A router has all of the features of a bridge, but it can switch packets across multiple networks. Routers can also determine the best path for “routing” traffic and filter broadcast traffic on the local segment. Routers work at the Network layer of the OSI model. Not all network protocols will work with a router. For example, the NetBEUI protocol is not routable.

Gateway Gateways make it possible to connect different network architectures. Think of a gateway as a computer that acts as a translator between two networks that don’t speak the same language. It is an entrance to another network that controls traffic on your network.

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Connection Services When expanding a network beyond the local area cable boundaries, it is likely that you will need to connect to a third party’s cabling system. An example of such a system is the telephone company. When considering which connection service to use, be sure to take into account your throughput, the distance the data must travel, and the cost of the service. Carriers Carriers are the companies that we contract with to carry our data over long distances. They are providing the cabling, microwave, and satellite connections. When thinking of a carrier, we most commonly think of our local telephone company or one of the long distance carriers. Keep in mind that there are many carrier companies that provide many different services at a variety of rates. Be careful when choosing a carrier. Be sure to compare them on an equal basis and look for hidden costs. Just because the cost looks good, does not mean that it is the best value. When thinking of telephone lines, there are two levels of service to consider. The first is public dial-up network lines. These are our standard telephone connections. With dial-up networking, each computer must use a modem and establish a direct connection. Typically, these connections are slow and not very reliable. Some of the newer digital services will claim to have a speed of 56 Kbps, but connecting at this rate is rare. The second choice is leased, or dedicated, lines. These powerful full-time dedicated connections do not use a series of switches to complete the connection. Speed for leased lines can reach 45 Mbps.

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Chapter 7 – Expanding a Network WAN Overview When the physical capabilities and distance limits of a LAN need to be exceeded, items such as bridges, routers and communications services are used to create a WAN. These physically larger networks will appear to function the same as a LAN. Most WANs are a collection of LANs. WAN links can include any of the following: •

Cable Television Coaxial Systems

•

Fiber-Optic Cable

•

Microwave Transmitters

•

Packet Switched Networks

•

Satellite Links

Those using a WAN link to connect LANs will need to use CSU/DSUs. A CSU/DSU (Channel Service Unit/Data Service Unit) is a hardware device responsible for changing the frame type from whatever the LAN is using into a frame that will work on the WAN. It also changes the frame type back when frames are sent back. The CSU is responsible for both the signals received from the WAN, as well as those transmitted to it. The DSU is responsible for converting both the input and output between the frame types between the LAN and the WAN. It can regenerate the signal, if necessary, and deals with timing issues. You can also use ISDN adapters if you are using ISDN PRI for WAN connectivity. Communication between LANs will involve one of the following technologies: •

Analog

•

Digital

•

Packet Switching

Analog Connectivity Analog communication is the one that we are most familiar with. It is based on PSTN (Public Switched Telephone Network). There are two types of PSTN: dial-up lines and dedicated analog lines.

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The dial-up lines can be further classified as: Line Type Description 1

Basic voice.

2

Voice with some quality control.

3

Voice/radio with tone conditioning.

4

Data applications below 1200 bps.

5

Basic data.

6

Voice and data over trunk circuits.

7

Voice and data over private lines.

8

Voice and data over trunks between computers.

9

Voice and video.

10

Application relays.

Dedicated analog lines provide an instant connection. This is because you lease the line 100% of the time and therefore do not have to dial-in. The down-side of these lines is that you will have to pay for them 100% of the time instead of on an “as used” basis. Dedicated lines are far more expensive, but if you have sufficient traffic, they can be justified. Digital Connectivity When you need a faster, more secure line than can be provided by an analog connection, you need DDS (Digital Data Service). The primary reason for using digital lines is that they are 99% error-free.

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T1 is the most widely used type of digital line. It is capable of 1.544 Mbps transmissions. It can be used to transmit digital voice, data, and video signals. The following table lists the most common connection types:

Connection Type

T1/E1/OC1 Channels

Voice Channels DATA RATE (MBPS)

T1

1

24

1.544 Mbps

T3

28

672

44.736 Mbps

E1

1

32

2.048 Mbps

E3

16

512

34.368 Mbps

XDSL

N/A

N/A

Varies depending ISP; faster download than upload

OC-1

1

N/A

51.8 Mbps

OC-3

3

N/A

155.52 Mbps

ATM

N/A

N/A

Either 155.520 or 622.080 (can reach 10 Gbps)

The T1 and the T3 standard are American, whereas the E1 and the E3 are the European standard.

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Network + Training & Test Preparation Guide Circuit-switched Networks Circuit-switched networks set up a continuous direct connection between the individual calling and the one being called. POTS (Plain Old Telephone Service) or the telephone lines are the most common example of this type of network. Obviously, since the infrastructure of the phone line we use today was created long before the advent of the personal computer and the Internet, this particular type of network is not suited for most companies’ business needs. Standard PSTN lines have a very limited bandwidth of less than 56 Kbps. These lines can, however, be used for somewhat secure remote access by employing the use of virtual private networks (VPNs) and tunneling protocols.

Packet Switching Networks Packet switching is a means of providing fast, convenient, and reliable network messaging. A packet switched network provides multiple paths that packets could travel from source to destination. In older, X.25 based packet switched networks, each packet was examined at each step in the path to determine whether it was damaged. This made for a very reliable and very slow connection. Today’s networks use a different technology referred to as Frame Relay. With Frame Relay, a packet may be sent over multiple permanent virtual circuits (PVCs), all of which are considered reliable. For this reason, Frame Relay does not check the packet at each step in its route, so it can be both reliable and fast.

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VLAN Virtual LANs (VLANs) can be viewed as a group of devices on different physical LAN segments that can communicate with each other as if they were all on the same physical LAN segment. It is best understood as a “logical” LAN, which lays out hosts (computers, printers, etc.) by another means apart from how they are connected physically and geographically. An administrator might set up a VLAN based on certain departments within his company, or by the specific use of the computers, or any other logical means. This allows the administrator the luxury of modifying the VLAN, adding computers or adjusting resources, without having to change the physical picture of the network. This type of network is most closely associated with a “campus environment.”

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Advanced WAN Environments If the existing services available do not meet the needs of your WAN, you might consider some of the advanced WAN technologies. One of these may just provide you with the necessary bandwidth and speed that you need. ATM - Asynchronous transfer mode uses fixed length (53 byte) cells instead of packets. These cells can speed communication because the network always know exactly what to expect in regard the size of the next cell. These systems are designed to operate at a throughput rate of 1.2 Gbps. However, in actuality, they currently operate at as high as 622 Mbps with most commercial boards operating at 155 Mbps. ATM is not media dependent and will operate on coaxial, twisted pair, or fiber optic. It is, however, media limited. This means that the choice of media will limit the maximum speed of the network. ATM is relatively new and will require special hardware and bandwidth to reach its full potential. As well as the common voice and data, ATM can be used with FAX, video, audio, and imaging. FDDI - Fiber Distributed Data Interface is the basis of fiber optic communication. It was designed specifically for Token Ring networks and has a maximum ring length of 100 Kilometers (62 miles). It will support 500 computers and run at 100 Mbps. While not a good choice for WANs, it is a good choice for LANs that require large bandwidth and high speeds. Because it is fiber optic-based, it will provide a secure network that is immune to interference. ISDN Integrated Services Digital Network was one of the early digital services, and focuses on the home and business market, while using copper telephone wires. ISDN BRI (Basic Rate Interface), which is intended for use in the home or small business, has two 64 Kbps 174

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Chapter 7 – Expanding a Network B-channels for data or voice (128 Kbps), and one 16 Kbps D-channel for control. ISDN PRI (Primary Rate Interface), which is intended for use by large businesses, has twentythree 64 Kbps B-channels for data or voice (1.544 Mbps), and one 64 Kbps D-channel for control. SMDS SMDS - Switched Multimegabit Data Service offers high bandwidth at speeds of up to 34 Mbps. This service is provided by some local companies and works well for MAN installations (compatible with IEEE 802.6). SONET SONET (Synchronous Optical Network) is a fiber optic-based technology that specifies the speeds at which the equipment can multiplex signals from sources into high-speed carrier devices. It includes a set of signal rate multiples for transmitting digital signals on optical fiber (OCx). It is capable of transmitting voice, data and video at rates ranging from 51.84 Mbps (OC-1) all the way up to 40 Gbps (OC-768). SDH SDH (Synchronous Digital Hierarchy) is a standard technology for synchronous data transmission on optical media. Internationally, it is considered the equivalent of Synchronous Optical Network. To be more precise, it is the European equivalent of SONET, much like E1 is to T1. It carries all the bits from say, a call, within one transmission frame. It uses Synchronous Transport Modules (STM), like OCx with SONET. The data-rate can vary anywhere from STM-1 (155 Mbps) up to STM-64 (10 Gbps).

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Modems Expanding a network requires an understanding of the additional devices necessary to make the connections. As we have already learned, connecting a few computers to form a local area network requires cabling and network cards. The problem with these devices is that they all have limitations that prevent long distance communication. To increase our network beyond a few computers, or over long distances, requires some additional hardware that will overcome the limitations of the cables, network cards, and media. A modem is a device that makes it possible to communicate long distances over standard telephone lines or cable. The name is derived from the words MOdulate and DEModulate. Some of the basic functions of a modem are to: •

Convert digital signals used by computers into analog signals that can be transmitted via telephone lines.

•

Convert the parallel digital data into serial digital data.

Modems are available in both internal (standard expansion card) and external (connected to a serial port and has its own power supply) versions. Modems transmit data at various speeds. These speeds are measured as bits per second. Speeds will range from very slow speeds of 300 bps to 56,600 bps. FAX modems will send and receive data at speeds up to 14,400 bps. Originally modem speeds were measured in terms of Baud. The Baud rate equals the frequency in cycles per second that can be transmitted via telephone lines. With early modems, the Baud rate was equal to the bps. However, due to the physical characteristics of copper wire and the effects of transmitting signals over long distances, there is a limit of 2400 Baud. This limit cannot be exceeded without encountering signal distortion. To overcome this and increase the speeds of data transmission via modems, designers learned how to place several signals within one cycle. Therefore, a given Baud rate could transmit data at 2, 4, 8, etc. times as fast as the Baud rate. With this change, the term Baud has disappeared and been replaced with bps. Today, modems have reached a new technology limit of 56,600 bps. Modems are classified by a “V” rating. The following is a list of common “V” ratings:

Standard

bps

Notes

V.22bis

2400

An old standard. Sometimes included with the purchase of a computer.

V.32

9600

Sometimes included with the purchase of a computer.

V.32bis

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14,400 High-speed version of the V.32 standard.

Chapter 7 – Expanding a Network V.32terbo

19,200 Not officially a standard yet. Will only communicate with another V.32terbo.

V.34

28,800 Improved V.FastClass. Backwards compatible with earlier V. modems.

V.42

57,600 Backwards compatible with earlier V. modems – error correction standard.

V.90

56,600 56K modem standard – resolved competition for standard between US Robotic X2 and Rockwell K56 Flex standards.

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Remote Access Computing (RAS) One of the most common forms of expanding a network is through a Remote Access Server, or RAS (pronounced RAZ) connection. You may be more familiar with the term dial-up network (DUN). Actually, both of these terms mean the same thing. The difference is how each computer is being utilized. With RAS, the computer is acting as a server or gateway to a network and will receive calls via a modem from other computers. Dial-up networking is the client-side of the connection. For example, when you access your Internet connection from your computer at home (via a modem connection) you are establishing a dial-up connection –you are the client. On the other hand, the server that you call (your Internet Service Provider) is providing a RAS connection to you – it is the server that is providing the connection to the Internet for you. The difference between a simple computer (Windows XP or Windows 95/98) and a RAS server (such as Windows Server 2003) is the number of inbound connections. A system running Windows XP or Windows 95/98 will allow only one inbound connection, while a true server like Windows Server 2003 will allow 256 inbound connections.

Connecting Two Computers Establishing a remote connection can be either between two computers or between a remote computer and a network. Let’s first look at connecting two computers. Any two computers can be connected, either via modems and telephone lines, or directly via COM ports and a cable. When connecting two computers in close proximity (same room or building), all you need to do is connect a cable between a COM port on each computer. A COM port is a 9pin male connector (it can be 25-pin but this is not as common as the 9-pin) on the back of the computer. The trick is that you cannot use just any cable with 9-pin female connectors. You must use a Null-Modem cable. This is a specially wired cable that actually replaces the modem. Since the two computers are directly connected, there will be no need to connect to telephone wires or dial a number, so this cable eliminates that part of a modem connection. Also, the COM port provides the parallel to serial data conversion that is necessary to complete a connection. Both computers will have to run compatible software so that one will act as a server and the other as a client. There are many off-the-shelf software packages that will perform this type of communication. In addition, Windows XP has an feature called a direct cable connection. By running Network Connections Wizard and following the simple 178

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Chapter 7 – Expanding a Network instructions provided, you can connect any two Windows-based computers and share data with only a cable connection.

Making a RAS connection to a server is similar to a direct connection but, in this case, you will use a modem to establish the connection. The server you are contacting may be an individual computer or a server that provides access to a larger network. On the server side, the RAS software must be installed and running. With this in place, the server will answer the phone and allow the connection if you are an authorized user. On the client side, your computer will have to make the phone call and provide the necessary security authentication information to the server. Normally, the client computer will establish the connection via DUN software. Windows (95/98 and NT) has an accessory called Dial-Up Networking. From this accessory, you can set up the proper configuration for the connection and dial the appropriate number. RAS Protocols In order for any connection to work, both computers must be using the same protocol. RAS/DUN supports various connection protocols to ensure proper connections and security. These protocols are: •

SLIP (Single Line Interface Protocol)

•

PPP (Point-to-Point Protocol)

•

PPTP (Point-to-Point Tunneling Protocol)

•

IPsec (Internet Protocol Security)

•

L2TP (Layer Two Tunneling Protocol)

•

SSL (Secure Socket Layer)

•

TLS (Transport Layer Security)

•

Kerberos (Greek mythology – three-headed canine who guards Hades’ gates)

•

ICA (Independent Computing Architecture)

SLIP (Single Line Interface Protocol) Serial Line Interface Protocol is a standard protocol for connections using TCP/IP (Transmission Control Protocol/Internet Protocol). This is a relatively old standard (1984), but is still in use with some systems. While this was the protocol of choice for a Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide long time, in today’s networks it has several disadvantages. Some of these disadvantages include: •

It requires a static IP address for each node.

•

It transmits in text only.

•

It supports only TCP/IP.

•

It cannot encrypt logon information.

•

It’s only supported by RAS clients.

PPP (Point-to-Point Protocol) The Point-to-Point Protocol was designed as an upgraded protocol to SLIP. With the rapid growth of the Internet and remote communications, the limits of SLIP caused many problems. PPP was intended to overcome these limitations and is very common today. Some of these improvements include: •

Support for TCP/IP, IPX, NetBEUI, AppleTalk, and DECnet.

•

It supports encrypted passwords.

•

It provides data compression and error control.

•

It provides security.

PPTP (Point-to-Point Tunneling Protocol) Point-to-Point Tunneling Protocol (PPTP) provides for a secure encrypted tunnel for communication through the Internet. This is accomplished by encapsulating one protocol with another protocol, such that only the sender and the receiver can accurately interpret the data that is being sent. Many organizations are using tunnels, created by PPTP and other tunneling protocols, as a less explensive alternative to costly leased lines. •

Secure transmission over TCP/IP networks.

•

It enables highly private network links over the public Internet.

•

Encrypted Connections.

•

VPN (Virtual Private Networks).

•

RAS and Security.

IPsec IPsec (Internet Protocol Security) is a framework of open standards for security at the Network layer of the OSI model. It is designed to protect IP packets as well as to provide defense against network attacks. It can be used in conjunction with VPNs (Virtual Private 180

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Chapter 7 – Expanding a Network Networks) and remote access for users who need access to resources on a private network. It is based on an end-to-end security model, meaning that the computers, both sending and receiving, are the ones aware of the IPsec transmission. It is transparent to the user. IPsec allows for either ESP (Encapsulating Security Payload) or AH (Authentication Header). ESP, which is the highest security method, authenticates the sender of data and encrypts the data as well. AH only authenticates the user. Kerberos V5, certificates (like X.509) and preshared keys can be used for authentication in conjunction with IPsec. L2TP Layer Two Tunneling Protocol (L2TP) is the latest version of the tunneling protocol. Unlike PPTP, it does not require IP connectivity. It combines Cisco’s Layer 2 Forwarding (L2F) with PPTP. It functions at the Data-link layer of the OSI model and is used in conjunction with VPNs. L2TP offers many advantages over PPTP, most relating to higher security. SSL The Secure Sockets Layer (SSL) is a protocol for addressing the security of an Internet transmission between a client and a server. It uses a key to encrypt the data, usually a user’s credit card number. It is included in both Microsoft’s Internet Explorer and Netscape’s Navigator and it is a complimentary addition to HTTPS, discussed here in the next chapter. TLS TLS (Transport Layer Security) is the evolution of SSL. It can work with SSL and uses Triple DES encryption (three 56-bit keys). Kerberos Kerberos is a secure method for authenticating a request for a service in a computer network. It allows a user to request an encrypted ticket, or virtual proof-of-identity cards so the user can request a service from a server. It does not provide authorization; it only establishes the user’s identity.. Windows 2000 and Windows Server 2003 Active Directory use this type of security by default, as does Novell Directory Services (NDS). . ICA (Independent Computing Architecture) ICA is a remote connection established using Citrix software (like WinFrame or MetaFrame) and a thin client environment. Thin clients are computers with no hard drive, a bare-bones operating system (such as Windows CE), limited RAM, and a processor in the range of 200 MHz to 300 MHz. ICA can be used with Windows, UNIX, Linux, and Macintosh computers.

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Network + Training & Test Preparation Guide In addition to providing remote sharing of information, RAS provides several layers of security. As with all security measures, you must implement or enable them during configuration of the RAS server. Here is a summary of RAS security functions: Auditing The server can create and maintain an audit trail of all connections. This audit can include who signed on and when they signed on. Callback Security One method of providing both security and cost control is to require the server to callback anyone that attempts to logon. By requiring RAS to call back to the client that is requesting a connection, you can restrict the numbers that RAS will call, therefore ensuring that the connection is legitimate. This feature can also be used to ensure long distance charges are charged to the company rather than the caller. This is a great benefit for those who travel for business and need access to the network. Security Host (Bastion Host) A security host or bastion host is a separate server that works between the RAS server and the client. This provides for additional authentication, and thus more security. Installing and Configuring RAS Installing RAS on a server is dependent on the network operating system installed on the server. Before installation, you will have to collect all the information from your operating system supplier to ensure that you have everything necessary. In addition, you will need to collect data on the type of connection you intend to make and the specifics of the computer hardware and network. At a minimum you will need to know the following: •

Your modem specifications including having the appropriate drivers for your network and/or computer operating system.

•

The type of communication port you intend to configure.

•

Are there any client protocols that will have to be enabled?

• What are the security requirements of the connection/network? Troubleshooting a RAS setup While not usually complicated, installing RAS can be frustrating. If it does not work the first time, you will have to carefully go through all the configuration parameters and check every one. All it takes is one number or check mark out of place to prevent the connection from working properly. Be sure to check everything including the RAS configuration, the modem configuration, and any other software that might use the modem. If another software package has “control” of the modem, your new RAS system may not be able to gain access.

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Chapter 7 – Expanding a Network Limitations of RAS As good as RAS is, it is not always the solution for every network. As a networking professional, you will need to understand both its strengths and weaknesses. You should consider RAS when your bandwidth is less than 128 Kbps, you want to keep the costs down, and you don’t need a fulltime connection. The latest Microsoft server operating systems such as Windows 2000 Server and Windows Server 2003 have wizards that make installing an RAS server much simpler.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book. Keyword Analog Signal Bridge Carrier Concentrator CSU/DSU Digital Signal DUN Frame Relay Gateway Hubs ICA Ipsec ISDN Kerberos L2TP MAU PPP PPTP RAS Repeater Router SDH 184

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Definition

Chapter 7 – Expanding a Network Keyword

Definition

SLIP SMAU SONET SSL T1 VLAN X.25

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Review Questions Chapter 7 1. What is the difference between a hub and a MAU? 2. What is the difference between an active hub and a passive hub?

3. Define a repeater, a bridge, a router, and a gateway.

4. What is analog communication?

5. A form of digital line that is capable of 1.544 Mbps transmissions is called?

6. Name three advanced WAN environments.

7. What are the two components of remote network accessing?

8. Name three RAS protocols.

9. Name four forms of RAS security.

10. Describe the difference between BAUD and bps.

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Chapter 8 – TCP/IP Essentials Introduction to TCP/IP TCP/IP is an internet (between network) protocol. It is also used with Ethernet networks, intranets, and the Internet. Transmission Control Protocol (TCP) is the most common Transport layer protocol (based on the OSI Model). TCP is built on top of IP (Internet Protocol), and is usually seen in the combination, TCP/IP. TCP/IP was developed by the Department of Defense agency (DARPA) in the 1960s as part of a military research project. TCP/IP was designed to accommodate a large internetworking environment comprising several different types of computers. From this beginning, it has evolved into the protocol of the Internet. This is the most common protocol suite with which a networking professional works. It is important for the networking professional to know that TCP/IP is used on the Internet and that it can be used with almost any network operating system. RFC (Request For Comments) A series of documents called RFCs (Request For Comments) serve as the standards that were used in the development of TCP/IP. Although RFCs are not true standards (they are documents that describe work in progress), some are considered to be Internet standards. These standards, as well as Internet standards, are the responsibility of the IAB (Internet Activities Board). The TCP/IP protocol suite includes a number of protocols, such as SMTP, SNMP, and FTP, which will be discussed later in the chapter. TCP/IP is a routable protocol that provides full duplex connections. Full duplex means that data can travel in both directions at once. Its popularity is largely attributed to the fact that it is not owned by a specific vendor. TCP/IP is an open protocol and is considered to be an industry standard. Also, these protocols were available on UNIX early on, and were even built into the Berkeley Standard Distribution, known as BSD UNIX. TCP/IP is now the standard on all versions of UNIX, and is in fact, the recognized standard for internetworking altogether. The TCP/IP suite consists of four layers. Each layer maps to one or more layers of the OSI model. The four layers are: Application, Transport, Internet and Network Interface.

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The four layers that make up TCP/IP provide a guideline for this model. There are actually five protocols that work within these layers to provide network connections. These five protocols are:

190

•

TCP- Transmission Control Protocol

•

UDP – User Datagram Protocol

•

IP – Internet Protocol

•

ICMP – Internet Control Message Protocol

•

ARP – Address Resolution Protocol

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TCP/IP Protocols As a network technician, and for the Network+ exam, you will not have to be an expert on the workings of TCP/IP. However, you will need to know the various protocols and how they relate to the OSI model. The Top Five TCP/IP Protocols As mentioned earlier, there are five major protocols used within TCP/IP. Let’s take a look at them. TCP Transmission Control Protocol (TCP) functions at the Transport Layer of the OSI Model. Its job is to ensure that data transferred from one computer to another reaches its destination intact. TCP breaks data into tiny chunks, called packets, or into even smaller units of measurement called datagrams. It then routes the information to its destination, and reassembles the data. This data exchange can be verified at various checkpoints. Should lost or corrupted packets be detected, they can be retransmitted in a timely manner. TCP operates by first establishing a connection-oriented session through the use of ports and sockets. It will then use the concept of sliding windows and acknowledgements to ensure fast and accurate data transmission. Let’s take a look at how this works. On a TCP/IP network, the origination point and destination point of the computers between which data travels are called ports. A port is a virtual outlet that can be opened on a network device. Port numbers are generally predetermined and correspond to a specific service that is running on a machine. Port numbers for some protocols are better known than others. The following list provides a few examples:

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For:

Use Port

FTP

21

TELNET

23

SMTP

25

HTTP

80

POP3

110

Chapter 8 – TCP/IP Essentials The sending computer’s address is called the source port number, and the receiving computer’s address is called the destination port number. The addresses, or port numbers, consist of a unique 16-bit numeric address ranging from 0 to 65,535. The well-known ports are associated with the range of possible port numbers from 0 through 1023. The registered ports are associated with the range from 1024 through 49151. The private or dynamic ports are associated with the range from 49152 through 65535. When you open a dial-up connection to the Internet, and specify a certain protocol, i.e. FTP, HTTP, Telnet, etc., you are automatically connected to the correct port for that particular data type. Although the terms, “port” and “socket” are often used interchangeably, a port is different from a socket. The port number identifies the application associated with the data. A socket is the combination of an IP address and a port number. Connection-Oriented Communication means that direct communication is established between two machines. This communication is called a session and is used to provide guaranteed delivery between the two machines. Acknowledgements are used to ensure the reliability of the data being transmitted. For each packet sent, an acknowledgement of receipt is returned. Think of it as a return receipt like the one you get from the Post Office when you want to be sure that a package has been delivered. Sliding windows are used to increase the speed of data transfer. This allows a receiving machine to collect packets out of order and hold them in a buffer until all packets in a specified group are received. Both machines have a sending and receiving window to buffer the data flow. Transmission speed is increased by sending a window of information at a time without having to get an acknowledgment back for each packet. Both machines keep track of the data so that any packets not received can be resent. UDP User Datagram Protocol (UDP) is a connectionless protocol residing on the Transport layer of the OSI Model. UDP transports data, but does not acknowledge delivery, nor does it check for errors. UDP packets are delivered through ports and sockets and do not require the opening of a session. The advantage of UDP over TCP is speed and is often used when transmitting streaming audio or video. IP Internet Protocol (IP) is the Network layer part of TCP/IP, which is responsible for moving the data from its origination point to its destination point. IP is connectionless, meaning that it establishes an end-to-end connection and starts transmitting without swapping control information. TCP tells IP that the data has arrived at its destination. If the transmission has not been successful, TCP will retransmit the data. IP merely routes the data, inserting its own header into the datagram when it is received from TCP. The IP header consists of the source and destination addresses, the protocol number, and a

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Network + Training & Test Preparation Guide checksum. The IP header is necessary so that gateways are able to determine where to route the datagram. Note: A checksum is simply a calculation that is performed on data by the sending computer. To be more specific, the checksum is the answer that is derived from this calculation. When the data arrives at the destination computer, the receiving computer performs the calculation. If the checksum is the same, the data is assumed to have arrived intact. The following are key elements of IP: Addressing – provides the address of both the sending and receiving machines. Broadcast – provides broadcast addressing within a network segment. Fragmenting and Reassembly – if data packets are too large for the underlying network, it will be broken down into a manageable packet size for transport. Routeability – provides routing information from one network to another. Time to Live – provides TTL data. This defines the number of hops a packet can make before it is discarded. ICMP Internet Control Message Protocol is part of the Internet layer. It is responsible for errors and messages regarding delivery of IP datagrams. ARP The Address Resolution Protocol is responsible for keeping track of the mapping of IP addresses to physical addresses. Each device on the network maintains an ARP cache. This cache contains a list of all the devices with which it is communicating. The contents of a cache can be displayed by using the ARP.exe command in Windows or the /sbin/arp command under UNIX. Other TCP/IP Protocols In addition to the top five, TCP/IP uses several other protocols: POP3 Post Office Protocol Version 3 (POP3) allows the client computer to retrieve E-mail from a POP3 server using a temporary connection. IMAP4 Internet Message Access Protocol (IMAP) is also a protocol for accessing email from your local server. Your Internet server holds your incoming email until users logon and download it. It is more advanced than POP3 because you can use folders and mailboxes on the server, run searches, or access multiple mail servers. 194

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Chapter 8 – TCP/IP Essentials POP and IMAP allow a client to pull their mail from a server. Simple Mail Transfer Protocol (SMTP), a protocol for transferring e-mail between points on the Internet, which is what you use when you send out mail. SMTP is server to server, whereas POP or IMAP are client to server. SMTP Simple Mail Transfer Protocol (SMTP) is a server-to-server protocol that acts under the control of the message transport system. SMTP is used to transfer E-mail between computers, usually over the Internet. An easy way to think of it is SMTP stands for “Send Mail To People.” SNMP Simple Network Management Protocol (SNMP) is the Internet protocol that manages nodes (individual computers) on an IP network. SNMP is not limited to TCP/IP. FTP File Transfer Protocol (FTP) is a client-server protocol that allows a user to transfer files from one computer to another over a TCP/IP network. The user accesses a special directory hierarchy containing public access files, by typing in a user name, or the word “anonymous.” The password is the user’s E-mail address. Files may then be uploaded or downloaded between the computers. HTTP HyperText Transfer Protocol (HTTP) is a client-server protocol that is used on the World Wide Web (www) to access HTML documents, such as web pages. HTTPS HTTPS (Secure Hypertext Transfer Protocol) is a Web protocol that encrypts and decrypts, using SSL as a sub layer underneath HTTP, allowing access to a secure Web server. It uses port 443, the secure SSL port instead of port 80, the HTTP port. HTTPS, as well as SSL, allow for the use of X.509 digital certificates for authentication of a user.

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Naming Systems Naming conventions and addressing is a large part of networking and TCP/IP. Remember, we are working in two worlds, the computer world of numbers and our world of user-friendly names. Understanding the difference between these two worlds and how to work in both of them is an important part of networking. DNS Domain Name Service (DNS) is a network service that translates hostnames to IP addresses over a TCP/IP network. The network administrator defines and configures the DNS settings using a standardized lookup table. DNS functions like a telephone directory. The network administrator need only remember the host and domain names. A domain name server is a computer that "remembers" the user-friendly names of the other computers and their IP address numbers. For example, the domain bigcompany.com may have an IP address of 192.49.238.33. This allows users to simply remember the userfriendly name while the domain name server remembers the numbers used by the network computers. A domain is a group of computers that share a common general purpose, such as government, education, commerce, or interest. Internet domains are established in a hierarchical order. A Fully Qualified Domain Name (FQDN) consists of a hostname and a domain name. The Internet Network Information Center (InterNIC, also known as Network Solutions) controls the top-level domains. These domains require suffixes such as .com for businesses or .edu for educational institutions. It is also common practice for various companies to register domain names for you.

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Network + Training & Test Preparation Guide The following table lists some Internet domains:

.com

Commercial Organizations

.net

Networks (The backbone of the Internet.)

.edu

Educational Institutions

.org

Non-profit Organizations

.gov

Non-military Government Organizations

.mil

Military Government Organizations

.biz

Businesses

.pro

Professional

.info

Information services

.xx

Two Letter Country Code For instance, Big Company Inc. in Italy might be http://www.Bigcompany.com.it or in Australia www.Bigcompany.com.au. Also, .tv is gaining in popularity. Tuvalu is a small country, which receives financial benefit from the registration fees.

WINS In a Windows-based network, the Windows Internet Name Service (WINS) is used to resolve NetBIOS computer names to their IP addresses. This is a dynamic service and requires that the workstation register with the WINS server each time it logs on to the network. NETBIOS NetBIOS defines a session-level interface and a session management/data transport protocol so computers can converse in session mode or send messages without connection in datagram mode, leaving the responsibility for error-checking up to the application. A NetBIOS name is a unique 16-byte address (only 15 can be used for the actual name) used to identify a NetBIOS resource on a network. There are four node types: B-node (broadcast), P-node (peer-peer), M-node (mixed – B and P) and H-node (hybrid – P and B). 198

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Chapter 8 – TCP/IP Essentials HOSTS file HOSTS file is a static text file that maps host names to IP. It predates DNS. It must be manually created and changed. LMHOSTS file LMHOSTS is static text file that are used to look up and resolve NetBIOS names and IP addresses. It predates WINS and is rarely used today. It must be manually created and changed. IP Gateway A gateway is used to connect two networks with dissimilar protocols. For example, it could connect a LAN to the Internet. In order for a gateway to work with the Internet, it must be assigned a static IP address. This means that it is permanently assigned. It would be difficult to find if it were constantly changing. DHCP Assigning IP addresses is like assigning telephone numbers, sooner or later we will run out of numbers. In smaller isolated networks, IP address assignment is not a big problem and each workstation or device can have a static address. However, as the number of addresses required increases, you will sooner or later come up with a number shortage. To resolve this, IP addresses can be dynamically assigned. That is, assigned on an “as needed” basis. Each host will lease an address only for the period of time required. When not needed, the address can be leased to another host. To accomplish this, you will need to use Dynamic Host Control Protocol (DHCP). Upon logon a DHCP server will provide a client with an IP address, subnet mask, and a default gateway if needed. Notice that the IP addresses are leased. This means that they will expire after a specific amount of time. This is to prevent one user from monopolizing the connection. A lease can be renewed. When the term of the lease is at 50%, the client will send a request for renewal. If the demand for connections is low (there are spaces available), the lease will be renewed without interruption. If not renewed, the client will attempt to contact the DHCP server that issued it the IP address directly about every 5 minutes until it reaches 87.5% of the lease, at which time the client will broadcast a request to obtain an address from any available DHCP server. If all addresses are being used or a DHCP server does not respond, the lease will expire and the address will be assigned to another user. In this case, the original user will have to wait for an opening before getting another lease and a new IP address. BOOTP BOOTP (Bootstrap Protocol) is a protocol that is used by diskless workstations to obtain their IP addresses (as well as the server’s address and its default gateway) from a BOOTP server. BOOTP was the foundation of the Dynamic Host Configuration Protocol (DHCP).

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Network Connection Utilities NAT NAT (Network Address Translation) is the translation of an IP address used within an organization internally (private IP address) to an IP seen by the Internet (public IP address). It allows for use of one public IP address for many private IP addresses. NAT also acts as a type of firewall, since it keeps the private IP addresses hidden from the outside world. Actually, a NAT is just a device or program that translates one set of IP addresses to another set of IP addresses, but it is most often used between a private network and the networks public address or addresses. IP Proxy Servers Earlier, we talked about the client/server relationship in terms of the roles of various users and servers. In the case of a proxy server, it serves many clients through only one connection. The user is connecting to the Internet via a secondary source, i.e. the proxy server. Compare this to a “he said-she said” scenario where an intermediary delivers the message between two parties who do not speak directly to each other. The proxy server is a liaison between the two parties, who think they are communicating directly with one another. The proxy server is actually making a connection to another network or to the Internet on behalf of the client. The proxy server may function in the role of the server or the client, depending on the direction in which the communication is traveling at any given time.

ICS ICS allows computers within a network, like a LAN, to share a single connection to the Internet. It contains DHCP, NAT, and DNS. ICS allows multiple users to fully utilize that connection by performing different tasks at the same time. It can also work in conjunction with Routing and Remote access.

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TCP/IP Addressing IPv4 Enough talk about IP address names, let’s now take a look at IP address numbers. Network computers require a unique IP address so that the other computers on the network can identify them and be able to communicate with them. This IP address is a 32-bit binary number. A 32-bit binary number can represent (232) or 4,294,967,296 (4.2 billion) different numbers. Imagine how difficult it would be to have to remember a combination of 32 1s and 0s for each address. Although that is easy for a computer, it is not easy for us. To simplify these addresses, they are broken down into four octets. An octet is a group of eight binary digits and a period or “dot” separates these octets. Each of these octets represents a number from 0-256. The result is called a dotted decimal number. A basic knowledge of the binary numbering system is required to understand network addressing: The 32-bit binary number: 00100001001001110000100011000010 Broken down into four octets: 00100001.00100111.00001000.11000010 Each octet represents a number between 0-256: 1st octet:

0 0 1 0 0 0 0 1 ----------------------------------------------------------------16 8 2 1 128 64 32 4

Adding the values assigned to the “1” positions gives us a value of 33 for the first octet. 2nd octet:

1 0 0 1 1 1 0 0 ----------------------------------------------------------------128 64 32 16 8 4 2 1

The value of the 2nd octet is 39. 3rd octet:

0 0 0 0 1 0 0 0 ----------------------------------------------------------------32 16 8 4 2 1 128 64

The value of the 3rd octet in our example is 8. 4th octet:

1 1 0 0 0 0 1 0 -----------------------------------------------------------------128 64 32 16 8 4 2 1

And finally the value of our 4th octet is 194. So the dotted decimal address of our example is 33.39.8.194. If a network is internal and does not access the Internet, the administrator may assign an IP address to each computer (as long as the number is unique). Internet IP addresses, however, are assigned by the Internet Corporation for Assigned Names and Numbers (ICANN) and these IP addresses are further divided into classes. It is important that the networking professional have a basic understanding of these classes.

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Chapter 8 – TCP/IP Essentials IP Addresses The dotted decimal number is further broken down into two components. The octet(s) on the left represents the Network ID (Network ID) and the octet(s) on the right represents the Host ID (Host ID). The class of the IP address determines which octets identify the Network ID and which octets identify the Host ID. Within classes, the first octet on the left is always part of the Network ID and the last octet on the right is always part of the Host ID. The two octets in the center can be either assigned to the Network ID or the Host ID. Depending on the assignment, the network is divided into classes. The class can be determined by the value of the first octet. There are five common classes: A through E. For the Network+ exam, you should pay special attention the Classes A, B and C. Class A

01-126

(leading bit = 0)

Class B

128-191

(leading bit = 1)

Class C

192-223

(leading bits =11)

Class A Addresses If the network applying for Internet IP addresses is extremely large, only the first octet is used for the Network ID and all three remaining octets identify the host (Host ID). (A host may be any device on the network.) The first octet in a Class A address is always a number between 1 and 126. The example we used to define a dotted decimal address of 33.39.8.194 would be an example of a Class A address. The first octet (33) would identify the network (Network ID) and the rest of the octets would identify the host (Host ID) 39.8.194. The leading bit in the binary representation of a Class A address is always 0 (00000000). Class B Addresses This class is assigned to medium sized networks. The first two octets identify the network (Network ID) and the last two octets identify the host (Host ID). The first octet in a Class B address is always a number between 128 and 191. An example of a Class B IP address would be 129.39.8.194. In this case 129.39 would be the Network ID and 8.194 would be the Host ID. The leading bit in the binary representation of a Class B address is always 1 (10000000). Class C Addresses These are the most common and are used for smaller networks. In this class the first three octets are used for the Network ID and only the last octet is used for the Host ID. The first octet of a Class C address is always a number between 192-223. An example of a Class C IP address would be 193.39.8.194 where the Network ID would be 193.39.8 and the Host ID would be 194. The leading bits in the binary representation of a Class C address are always 11 (11000000). Class D and Class E Addresses Class D cannot be used for networks (multicast) and Class E IP addresses are reserved for future use.

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Network + Training & Test Preparation Guide Since a Class A Network ID uses the remaining three octets to assign numbers for the Host ID, there are 16,777,214 possible Host ID numbers. Likewise, Class B uses two octets for the Network ID and two octets for the Host ID, there are only 65,534 possible Host ID numbers. Class C uses three octets for the Network ID and only one for the Host ID, so there are only 254 addresses available for hosts. You can see that Class A has the largest number of hosts, with the least number of Network IDs. Also, Class C has a large number of Network IDs and only a few Host IDs. Note: The existing shortage of addresses has made it impossible to obtain a Class A address for a long time. Some IP Addresses are reserved for special purposes: If:

Network ID

Host ID

IP Address

All Zeros

This Network

This Node

Default Route for RIP

All Ones

All Networks

All Nodes

Broadcast

127

Local Node

It is important for the networking professional to be able to identify whether an IP address is a Class A, B or C address. Use the following table to memorize the different classes: CLASS A

1 - 126

CLASS B

128 - 191

CLASS C

192 - 223

In addition, there are some IP addresses that are reserved for special purposes: Addresses that begin with 127 and 224 through 255 are used for testing purposes and for multicasting and are not available for normal host addresses. (For example, the Network ID of 127 designates the local node and allows that node to send a test packet to itself without generating network traffic. This is the loopback address, specifically 127.0.0.1) Class A - used by very large networks. All in use and no longer available. Class B - used for medium-sized networks. Class B IP addresses are all in use and no longer available. Class C - used for smaller networks that do not exceed 254 hosts. Class C IP addresses are still available. As we mentioned earlier, if a network is going to be connected to the Internet, you must petition the official Internet authorities for the assignment of a network address. This organization is called InterNIC (Internet Network Information Center), and they are responsible for the assignment and regulation of IP addresses. 204

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Chapter 8 – TCP/IP Essentials Contact InterNIC at: Network Solutions InterNIC Registration Services 505 Huntmar Park Drive Herndon, VA 22070 You can also E-mail to [email protected]. IPv6 (IP Next Generation) IPv6 (IP Next Generation) is the latest IP technology. It uses 128-bit addressing, as compared to IPv4, which only uses 32-bit addressing. It does, however, demand high bandwidth. The benefits of IPv6 include improved scalability, as well as ease of configuration and security built right in. IPv6 uses hexadecimal numbers (0 to 9, then A to F) instead of decimal because of the length of the new addressing scheme. It uses eight 16-bit pieces with colons as separators as opposed to the full stops used in IPv4. An example of IPv6 is as follows: AAAA:BBBB:0000:0000:0000:0081:FFFF:DDDD A shorthand version of the previous IPv6 address: AAAA:BBBB:0:0:0:81:FFFF:DDDD Leading zeros can be taken out, but at least one must be left in each 16-bit field. You can compact multiple fields of zero beyond the previous example. This happens to supercede the rule about one zero having to be left in a field. A double colon can be used to represent multiple contiguous fields of zeros. For example, the following address 0000:0000:0000:0000:0000:0000:0000:0000 0000:0000:0000:0000:0000:0000:0000:0005 can be represented in their compacted form by :: ::5 You cannot, however, use the double colon more than once in an IPv6 address. It would make it unclear as to what was represented. Rather than having “classes” like IPv4, IPv6 uses format prefixes (FP), which are variable-length fields that comprise the high-order bits, to define the address type. The address types are Unicast, Anycast, and Multicast. Unicast is an address for a single host. Here is an example of a Unicast address: 1070:0:0:0:7:777:300F:754B Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Unicast addresses can be broken down further into four sub-groups: Global aggregatable address, Site-local address, Link-local address and IPv4-compatible address. An aggregatable global address uses a fixed prefix of 2000::/3. A Site-local address uses the prefix FEC0::/10 and can be regarded as private addresses, since they can be used to limit traffic to a domain. Link-Local addresses use the FE80::/10 prefix and are used by hosts on a local link. Finally, IPv4-compatible IPv6 addresses have zeros in the section beyond the normal IPv4 32-bit address (0:0:0:0:0:0:A:B:C:D or ::A:B:C:D) Anycast is an address for a set of interfaces that typically belong to different hosts and is delivered to the closest one. Multicast, which replaces broadcast, is an address for a group of hosts within a scope and has a FF00::/8 prefix. The Loopback address in IPv6 is 0:0:0:0:0:0:0:1 or ::1, just like 127.0.0.1 with IPv4. All in all, IPv6 allows for a multitude of IP address possibilities for the future of networking.

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Subnetting Subnetting is the process of creating more than one private network from one public network address by customizing your subnet mask. For example, a large university may have a network spread over several buildings and perhaps remote campuses. By using subnets, you can reduce the overall network traffic. In this example, all the traffic within a building or campus will be kept locally except when it needs to go to another subnet. Since a router connects each subnet, only the traffic that is not local will pass through. By using a concept called anding, a router can determine which addresses are local and which addresses are for other subnets within the network. Anding is the binary addition that the router uses to make this determination. Before looking at anding, lets look at subnet masks. A subnet mask is an IP address (dotted-decimal number) in which all ones represent the network portion of the IP address and all zeros represent the host portion of the IP address. For example: 11111111.11111111.00000000.00000000 or 255.255.0.0 In regard to classful addressing , a subnet mask can be 255.0.0.0 (Class A), 255.255.0.0 (Class B), or 225.255.255.0 (Class C). The number of 0s determines the maximum number of available hosts within the sub-network.

Default Subnet Masks 255.0.0.0

Class A (16,777,216 hosts)

255.255.0.0

Class B (65,534 hosts)

255.255.255.0

Class C (254 hosts)

Note: You cannot use IP addresses with all 1s or all 0s. You can use a subnet mask that does not completely use all the bits in an octet. You must however, have all 1s to the left and all 0s to the right. Subnet masks with full octets (255) are the default subnet mask. The purpose of a subnet mask is to determine the network portion of the IP address, separating it from the host portion of the address. This is done with binary addition (anding), which uses a certain logic to determine the network portion of the address. If you “and” the IP address to the subnet mask, the results will be the actual network portion of that IP address (not necessarily the default network portion determined by its class). Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Remember, for binary addition: 1+1=1 1+0=0 0+0=0 Now, using our previous example of 33.39.8.194, let’s and it to the subnet mask of 255.224.0.0. 00100001.00100111.00001000.11000010 (33.39.8.194) 11111111.11100000.00000000.00000000 (255.224.0.0) equals 00100001.00100000.00000000.00000000 (33.32.0.0) Noticing that all the places that have ones, and through leaving only the digits for the network portion or 33.32.0.0, while the Host ID 0.7.8.194 is determined by the zeros in the subnet mask. By using this method, a router can determine if a message is for a destination on the local network or for a machine on a remote segment. Any local addresses will not pass through, thus reducing the traffic on the rest of the network. It is common in TCP/IP to omit the trailing octets in the Network ID and the leading octets in the Host ID. Therefore in our example the Network ID is 33.32 and the Host ID is 7.8.194. Since the subnet mask only goes 3 bits into the second octet, it recognizes the first 11 bits as the network portion of this address. Those 11 bits equal a network portion of 33.32. The remaining 21 bits in the IP address is the host portion This equals 7.8.194. The network and host portions do not break down neatly into octets since the subnet mask does not take up a complete second octet. The following tables summarize IP addresses and subnet masks:

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Chapter 8 – TCP/IP Essentials Default Subnet Mask and Network Classes

A

001.a.b.c to 126.a.b.c

255.0.0.0

B

128.a.b.c to 191.a.b.c

255.255.0.0

C

192.a.b.c to 223.a.b.c

255.255.255.0

Maximum Networks and Hosts per Class

A

255.0.0.0

B

255.255.0.0

C

255.255.255.0

126

16,777,216

16,384

65,534

2,097,152

254

How to Subdivide a Network The process of subdividing a network into logical units is called subnetting or subnetworking. There are several reasons to divide a network in this manner. •

Connect physically remote local networks.

•

Connect a mix of network technologies (Ethernet and Token Ring).

•

Allows an unlimited number of hosts to communicate.

•

Reduce network traffic by limiting broadcast and local traffic to a single segment.

There are steps to follow when subnetting: Determine the number of Network IDs required. A unique network ID is required for each subnet and each wide area network. Be sure to include some room for growth of the network. Determine the number of Host IDs per subnet. A unique host ID is required for each TCP/IP computer network interface card, each TCP/IP printer network interface and each router interface on each subnet. If a router is connected to two subnets, it will require an address for each subnet. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Define the Subnet Mask The goal is to define one subnet mask for the entire internetwork that gives the desired number of subnets and allows enough hosts per subnet. To begin this process, you will need to start with the network ID supplied by InterNIC. We will use an InterNIC ID of 191.36. First, we will notice that this is a Class B network and therefore the default subnet mask will be 255.255.0.0. With this number, we have one network with approximately 65,000 hosts. As we begin to subnet, we are increasing the number of network addresses that we can use and decreasing the number of host. We do this by using bits from the next octet or octets as part of our network addresses that we assign. You should remember the formula 2n-2 where n is the number of bits borrowed. We use this formula to determine the number of subnets that will be created by borrowing bits from the hosts. The following table shows the subnet mask created by borrowing bits and how it will affect our network.

210

Class B Subnet Mask (2 to 14 bits borrowed)

Bits

Subnets

Hosts

255.255.192.0

2

0

N/A

255.255.224.0

3

6

8190

255.255.240.0

4

14

4096

255.255.248.0

5

30

2046

255.255.252.0

6

62

1022

255.255.254.0

7

126

510

255.255.255.0

8

254

254

255.255.255.128

9

510

126

255.255.255.192

10

1022

62

255.255.255.224

11

2046

30

255.255.255.240

12

4096

14

255.255.255.248

13

8190

6

255.255.255.252

14

16,382

2

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Class C Subnet Mask (2 to 6 bits borrowed)

Bits

Subnets

Hosts

255.255.255.192

2

0

N/A

255.255.255.224

3

6

30

255.255.255.240

4

14

14

255.255.255.248

5

30

6

255.255.255.252

6

62

2

To make this easy, you can use the scientific calculator supplied with any Windows operating system. For this example, lets keep our network ID of 191.36 as assigned to us by InterNIC. We already know that the first two octets will be 10111111 00100100 from this ID, the question is how many bits of the third octet do we need to use? After examining our network requirements, we determine that we will need 14 subnets to meet our current needs. Just to be on the safe side, let’s add 4 more for future expansions, giving us a total requirement of 18. Now we get out our Windows calculator. Make sure that it is in scientific view (that’s the big calculator).

1. Make sure that the decimal mode (Dec) is selected. 2. Enter the value of 18. 3. Change the mode to binary (Bin). The number 18 will now be in binary (10010).

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4. Count the number of binary digits (5). This will be the number of bits required for the third octet. This will actually allow us up to 30 subnets with 2,000 hosts each. Also notice that had we chosen 14 (no allowance for growth), our answer would have been to use 4 bits and we would have been limited to a maximum of 14 subnets. Had we needed to add a new subnet, we would have had to reconfigure the entire network, instead of selecting the next subnet on our list. For this example, the subnet mask would be 255.255.248.0. Determine the Network IDs One you determine the number of subnets required and the subnet mask, you can determine the available Network IDs. To keep things simple, let’s look at the subnets for the subnet mask of 255.255.224.0 and the network address of 192.36. The following table shows the six subnets created when using the three bits of the third octet:

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Subnet Mask 11111111 11111111 111 Binary Network ID

Dotted-decimal ID

11000000 00100100

192.36 (overall network address)

11000000 00100100 001

192.36.32

11000000 00100100 010

192.36.64

11000000 00100100 011

192.36.96

11000000 00100100 100

192.36.128

11000000 00100100 101

192.36.160

11000000 00100100 110

192.36.192

Determine the Host IDs The host ID can be assigned as any number starting with the last digit of the forth octet (00000001), up to and including the remaining digits not used with the subnet ID. In dotted-decimal format, this means that the number starts with .001 in the last octet, and continues up to one less than the subnet ID of the next subnet. The only restrictions are that you cannot use .000 or .255; these are reserved for broadcast addresses. Summary of Subnets Subnet masks are used on TCP/IP networks to determine whether a message is for a computer that resides on the local network, or one that is located on a remote network. For example, on a Class A network the default subnet mask would be 255.0.0.0. This indicates that the Network ID is located in the first octet of the network address. A Class B network default subnet mask would be 255.255.0.0 and the default Class C subnet mask would be 255.255.255.0, indicating that the Network ID is contained in the first two or three octets respectively. The zeros indicate the location of the Host ID. The sending computer checks the octets of the destination address against its own to determine if the destination computer is on the local network or a remote network. (If the sending computer and the destination computer have the same subnet mask, they are on the same network. If it is different, the sending computer will send the message to a router for delivery.) Specialized Solutions, Inc.

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214

DEFAULT SUBNET MASK

CLASS ID

CLASS A

255.0.0.0

CLASS B

255.255.0.0

128 - 191

CLASS C

255.255.255.0

192 - 223

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TCP/IP Configuration Concepts The Windows Registry database contains the TCP/IP configurations, in addition to other hardware and software configurations. Only administrators who have detailed knowledge and experience working with the Registry should attempt to change the default TCP/IP parameters in Registry Editor. However, other TCP/IP settings may be established or changed by first clicking on the Network icon in the Control Settings window. Next, click the Protocols tab, right-click on TCP/IP Protocol, and click Properties. This opens the TCP/IP Properties window and you can now click on the appropriate tab and enter your configuration information. The appearance of these dialog boxes may vary depending on which operating system you are using.

IP Address Here, you may specify a particular IP address, or click the radio button next to “Obtain an IP address automatically,” and the computer will capture one from the DHCP server. DNS You can enable or disable DNS. Click the radio button to enable DNS, and enter the information in the appropriate fields. Default Gateway Type the IP address of the gateway routers you have installed on your network. Use the “New” and “Add” command buttons to add a new gateway to the list of installed gateways. Whichever one appears first on the list is considered the default gateway. On some screens, you will need to type in the specified default gateway.

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Network + Training & Test Preparation Guide WINS Windows Internet Naming Service (WINS) is central to Microsoft’s networking topology. WINS maps NetBIOS names to IP addresses. DHCP Dynamic Host Configuration Protocol (DHCP) is used on a TCP/IP network to send configuration data to clients. This information includes the TCP/IP address configuration, default gateway, and subnet mask configuration. It also includes the DNS configuration.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword

Definition

ARP BOOTP Class A IP Address Class B IP Address Class C IP Address Default Gateway DHCP DNS FTP HOSTS file HTTP HTTPS ICMP ICS IMAP4 IP IP Address LMHOSTS file NAT NetBIOS Octet Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Keyword POP3 Port Number Proxy Server SMTP SNMP Subnet Mask Subnetting TCP UDP WINS

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Definition

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Review Questions Chapter 8 1. What are the four layers that make up the TCP/IP protocol suite? 2. How many primary protocols are used to make the TCP/IP Suite?

3. Name three of the five other protocols used within TCP/IP.

4. What is the purpose of DNS?

5. What is an FQDN and give an example?

6. What is a domain?

7. Who is responsible for maintaining top-level domains?

8. Which of the name resolution services will work only in Windows?

9. IPv4 addresses consist of a ______ bit number.

10. What is the value of the leading bit (one on the far left) for a Class A IP address? Class B? Class C?

11. Subnetting is the process of breaking an IP address into _________ and ________ groups.

12. What are five reasons to use subnetting?

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Chapter 9 – TCP/IP Utilities

Chapter 9 – TCP/IP Utilities One of the advantages of using TCP/IP as your network protocol is that it comes with several utilities that you can use to validate and troubleshoot the network. In addition, you can obtain several third party software packages that will help you manage a network.

Network Managers - SNMP Simple Network Management Protocol (SNMP) is an open protocol that allows third party software vendors to create products to manage networks. Using one of these products, you can remotely monitor any SNMP compatible device. The following are several SNMP managers: Hewlett-Packard Open View IBM NetView InterMapper (Macintosh) MRTG (Multi Router Traffic Grapher – UNIX) NetMinder Sun Net Manager SNMP utilizes three elements for the complete system: The management system software The agent software Communities Management Software This is the primary software package that is used by the administrator. It is run on a single computer and is used to access any SNMP devices and collect data. The data is then compiled in a database called a MIB (Management Information Base). From the database and the software interface, the administrator can create reports and charts that define the status of the network.

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Network + Training & Test Preparation Guide Agent Software The agent software resides on the SNMP compliant device. It will respond to commands issued by the management software. The three commands are: Get: request data from the device. Get-next: request the next value in a sequence. Set: sends a configuration value to a device. An additional SNMP command is the trap. This command will capture any errors and problems that occur on the agent device and send it to the manager. Communities Communities are logical groups consisting of at least one manager and agent (usually several agents are assigned to one manager). The value of using communities is to limit the number of managers and agents. A community can also restrict access, therefore providing a level of security.

Validation Tools TCP/IP provides several command-level tools that can be used to validate various parameters within a network. These commands can be entered from a DOS prompt.

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Event Viewer Event Viewer is a Windows utility that will allow you to log any events and errors. This includes critical system errors, and TCP/IP events and errors. Note in the graphic below that an icon indicates that the event is critical (a stop occurred), serious (!), but did not cause a stop, and normal (i).

ROUTE The ROUTE command will show you the routing table and allow you to make edits to it.

NBTSTAT This command will display NetBIOS over TCP/IP statistics. Nbtstat -c provides the remote name cache with the IP addresses. Nbtstat -n provides local NetBIOS names. Nbtstat -r provides names resolved by both broadcast and the WINS service. Nbtstat -R both purges and reloads the remote name cache table.

NETSTAT This command will display all the TCP/IP protocol statistics. Netstat -a shows all connections and listening ports. Netstat -e shows Ethernet statistics. Netstat -r shows the content of the routing table. Netstat -s shows statistics on a per-protocol basis.

TRACERT A Trace Route command-line utility, TRACERT, shows every router interface that a TCP/IP packet passes through on its way to its destination. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Hint: Use these line commands by clicking the Start button in your taskbar, clicking Run, and typing in either cmd or command.

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Chapter 9 – TCP/IP Utilities

TROUBLESHOOTING TOOLS TCP/IP also provides several useful troubleshooting tools. The following three are the most common and are covered in more detail in the next chapter.

IPCONFIG/WINIPCFG These commands are the same, and will display the current configuration of a computer. IPCONFIG is entered from a DOS prompt and WINIPCFG can be used from RUN on the START menu.

IFCONFIG IFCONFIG displays the status of the network interface configuration. You should use this command when you want to verify a user’s configuration or if there are problems reaching a remote host.

ARP ARP will allow you to find the physical address (MAC address) of a computer by using the IP address of that computer. For example, the IP of a host might be 192.168.12.1, and you would use this IP to find its MAC address or its physical address, which might be 0000-05-67-FF-33. Arp -a displays the current ARP entries (resolved IP to MAC addresses) on your client. Arp -s is used to change the IP address of a device.

RARP RARP accomplishes the reverse of the ARP by using the known MAC address to find a host’s IP address.

PING The lowest level test to find out if you have connectivity to a remote host. Ping works at the IP level, and will often respond even when higher-level TCP-based services cannot. Ping -t performs a continuous ping and ping -n pings the IP address more than once.

NSLOOKUP This command is used to troubleshoot DNS problems and can display the DNS entry for a given IP address. NSLOOKUP -t shows all records of the type specified. NSLOOKUP a shows aliases of clients in the domain. NSLOOKUP -d shows all records for the domain. NSLOOKUP -h shows CPU and operating system information for the domain. NSLOOKUP -s lists well-known services of clients in the domain.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book.

Keyword

Definition

ARP Event Viewer IFCONFIG IPCONFIG Management Software NBTSTAT NETSTAT NSLOOKUP PING RARP SNMP TRACERT

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Review Questions Chapter 9 1. You are the manager of a large network and have been getting complaints about the system being slow. What kind of software package can you purchase to help analyze your network? 2. In order for your new network management software to monitor the activities of the entire network, each device will need to be _________ compliant. 3. TCP/IP provides several tools that you can use to validate statistics of your network. List as many as you can.

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Chapter 10 – Network Security

Chapter 10 – Network Security Security is a vital aspect of a network that cannot be ignored. Password practices and procedures, data encryption, and firewalls are critical parts of your network. Select a basic security model that will meet the needs of your network and customize it as your needs change.

User and Share Level Users will have different levels of access, depending on the roles they play in your company. All users will have access to the network and to their own files (documents they themselves have created). Most users will also be able to access shared files. Very few users will have access to administrative features, such as setting up E-mail addresses and initial passwords. There are a number of reasons for maintaining a secure network. Once a company’s files have been set up for maximum access, unless safeguards are built in, anyone can get into any file and do anything to it they want to do. Limiting access via passwords can prevent an inexperienced user, motivated by curiosity, from wandering into unprotected areas and inadvertently corrupting or deleting files. Although corrupting and deleting files accidentally can cause serious problems, you must also be prepared for the possibility of malicious intent. A disgruntled employee, or anyone who has access to your network for that matter, can deliberately damage your network, creating chaos and costing thousands, or even millions, of dollars. The best time to set up your network security, or at least have your plan intact, is right up front, before you set up the network. As you might have already deduced, the network administrator has complete responsibility for anything that happens to the network. Therefore, she must develop a plan that will meet the needs of her particular network. A good plan will include the following considerations: •

Size of network

•

Scope of network

•

Type and amount of usage of the network

•

Who will have access to what

User-level Security All employees should be assigned user names and passwords, as well as the levels of permission necessary for these individuals to do their jobs. Users should be held accountable for the security of their individual workstations. Most network security breaches are the work of someone from inside the company. Whether the sabotage is malicious, or an irresponsible prank, the results can be devastating.

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Network + Training & Test Preparation Guide Privacy and confidentiality are important to most users. If the user is not able to trust that the documents he or she creates are safe from outside access, the user will be inclined to be less attentive to personal security. Password protection is, among other things, a gesture of respect for the user and the system. It creates an atmosphere of confidentiality, and cultivates a conscientious attitude toward security. User-level security requires the user to logon using a Username and password. A verification method called “authentication” verifies the identity of a person or process. In a manner similar to the signature on a document, authentication confirms that messages received truly originated from their stated source.

Share-level Security With the share-level security model, passwords are assigned to network resources rather than to users. Users can access a shared resource, such as a template or another type of file. They can then copy the file to a local drive or a personal folder on the server. The user can edit the file as necessary, while the original file remains intact. Information on the shared drive cannot be changed by anyone other than the person who created the file. However, the file can be accessed by anyone who has the password and knows how to use it to access the shared resource. The systems administrator should have an assistant or backup person who will have total access to the system, should the administrator be unavailable at a time when administrator access is required. A roadmap of all user names and passwords should be kept in a secure place, where the administrator can easily retrieve it.

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Security Techniques There are a number of techniques and practices that will enhance the security of your network. Some will be more suitable to your system than others. Your security needs will determine which techniques will best meet your system’s needs. Firewalls A firewall is designed to prevent access to your network from outside the company. It is an important part of a network security plan. If you are accessing the Internet from your network, you will most likely be using E-mail, at the very least. A firewall will need to be part of your security plan in order to prevent unauthorized access from outside of your network. Some firewalls will only allow E-mail to pass through, or they can be configured to suit your specific security needs. Firewalls can trace calls and locate the computer trying to break in, but they are not particularly effective if your goal is to protect trade secrets or other types of proprietary information. They can permit or deny traffic at a certain level, they can be host-based, and work at the application level. Protocol-specific application proxy firewalls may provide increased access control, or auditing, by forwarding application traffic through the firewall. Gateway hosts (also called bastion hosts) create fortified areas in the network’s security perimeter. As the system administrator, you will be responsible for choosing the type of firewall that best meets your network’s needs.

Blocking Port Numbers You can block port numbers for security purposes on your firewall or router so as to allow only specific traffic into your network. For example, if you wanted to block Internet traffic from entering your intranet, you would block port 80. Backing up Data Another integral part of network security is your backup system. Files need to be backed up daily, and even more often on larger networks. This needs to be handled in such a way that production will not be interrupted, and your company’s files and directories will be safe and available when you need them. 232

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Chapter 10 – Network Security It may make more sense to have two medium-sized servers, rather than one larger server, so if one goes down the other can maintain network operations. Ideally, the second server should serve as a backup to the first. Most file server manufacturers recognize the need for data redundancy and thus, offer server equipment with multiple hard drives that mirror each other. If anything happens to one, the other can take over without compromising network operations. These multiple disks are called disk arrays, and are more commonly known as RAID. Another more common form of backup is to a tape drive. Although slower than RAID, it is still a viable option. Backup Options Before we discuss the different RAID fault tolerance strategies, let’s discuss the various backup methods that are available. As a computer professional, you know how important a backup plan is to the safety of your network’s data. Nothing will save you time and stress like an effective and thorough backup strategy in case the worst happens and your system crashes. While planning your backup strategy, you must answer important questions about what to backup, where you will keep the backup information (on-site or off-site), and how often backups will be performed. In addition, your plan will need to include information about who will be in charge of performing the backups, how the backup information will be tested, and the procedure to follow for recovery. Remember, those who fail to plan, plan to fail, so make sure not to neglect this important part of network security. There are several options available, called the backup medium, for performing and storing data backups: Removable Disks There are two categories of removable disks: Small-Capacity and Large-Capacity. As you might guess, the small-capacity category includes the floppy disk. Floppy disk capacities today, range from 1.44 MB for the standard floppy disk to up to 250 MB capacities for ZIP disks. This backup medium is suitable for small companies. Large-capacity disks include such options as the removable optical disk, which uses laser technology to read and write information onto a removable disk that has capacities of 128 MB to 650 MBs. Tape Backup This is probably the oldest and most popular backup medium in use today. The tape backup method is inexpensive and simple to implement. It also has large capacities of up to 50 GB for some systems. Specialized Solutions, Inc.

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Backup Software Software programs or utilities are available that make backing up data easier and more efficient. Most operating systems come with a backup utility, but usually these won’t have the features available on a third-party backup program. Full, Differential, and Incremental Backups There are three backup types available: Full, Differential and Incremental. The Full backup, as its name implies, will backup all selected data on the network. This method will take the largest amount of storage media, but will be the easiest to restore.. This type of backup is usually performed weekly. The Differential backup is used for backing up only the files that have changed since the last full backup. An archive bit is used to identify the files that have changed. When recovering from a failure, both the last differential backup tape copy and the last full backup tape copies will need to be used. The Incremental backup is used for daily backups. This will reduce the amount of time needed to perform backups to the server, as only the data that has changed since the last backup will be copied. This method also uses an archive bit to identify which files have changed. To restore, the last full backup and all of the incremental backup tapes will be needed. Volumes Volumes are a way to organize storage disks so that the network operating system can store data on a disk. It is a named portion or chunk of disk space. A volume can be part of a disk or an entire disk. Fault Tolerance and RAID The ability of a system or component to continue normal operations, despite the presence of hardware or software failures, is called fault tolerance. This usually involves some degree of redundancy, and utilizes different means of dealing with security issues at this level.

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Chapter 10 – Network Security The following are common RAID (Redundant Array of Independent Disks) specifications: RAID 0 - Non-redundant striped array (disk striping) RAID 1 - Mirrored arrays (disk mirroring) RAID 2 - Parallel array with ECC (disk striping with ECC) RAID 3 - Parallel array with parity (disk striping with ECC stored as parity) RAID 4 - Striped array with parity (disk striping with large blocks) RAID 5 - Striped array with rotating parity (disk striping with parity) NOTE: The acronym for RAID has also been referred to as: “Redundant Array of Inexpensive Disks.” Disk Striping (RAID 0) The segmentation of logically sequential data, such as a single file, so that segments can be written to multiple disk drives (or other physical devices) in a round-robin fashion is called disk striping. If your processor is capable of reading or writing data faster than a single disk can keep up, this relatively inexpensive technique can be very useful. However, if anything happens to one of the drives, the data in the stripe set is lost and cannot be retrieved. (Provides no fault tolerance.) Disk Mirroring (RAID 1) Disk mirroring or disk duplexing involves using one or more mirrors of a hard disk. The same data is written to two separate hard disks in order to preserve the data in the event of a device failure. This technique may be applied in either software or hardware, and is a standard feature of RAID systems. Several operating systems, including Novell NetWare, support either disk mirroring or disk duplexing. Disk Striping With Parity (RAID 5) The most common of RAID strategies, this one uses the parity method of ensuring that the data stored is really the same data that was sent. With this method, a copy of the data is spread across all of the disks based on a mathematical formula such that any one disk in the set can be lost and the other disks will have a copy of all of the information that it contained. If more than one disk is lost, then the data in the entire array is also lost. Typically, administrators are alerted when one disk fails so that they can “regenerate” the RAID set before another disk has a chance to fail. RAID 6 and Beyond RAID-6 includes a second disk striping with parity scheme, which provides for even more fault tolerance. This, however, is not being used commercially at the moment to an Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide large degree. RAID 7 offers a real-time operating system and the functionality of a standalone computer. RAID-10 is comprised of an array of stripes (each stripe equals a RAID1 array), which allows for better performance. Cost, as you might guess, is an issue. RAID-53. is like RAID-10, but uses a striping scheme where each stripe is a RAID-3 array of disks. Like RAID-10, it offers better performance, but at a greater cost. These types of RAID are not as commonly used and are not as likely to be on the test. Storage Area Network (SAN) A SAN (Storage Area Network) is a back-end network connecting storage devices (generally by using SCSI). A SAN can either be centralized or decentralized. A centralized SAN generally ties many hosts together into one storage system. A RAID system is the most common example of a centralized SAN. A decentralized SAN connects multiple hosts with many storage systems. SAN traditionally have been used for the purposes of archiving data that is needed but infrequently used. SANs are channel attached whereas NASs are network attached. Network-Attached Storage Network-attached storage (NAS) is hard disk storage (RAID) like SAN, but it is treated just like any node on the network and is subject to all the positives and negatives of that identity. It is assigned an IP address and it is attached to a LAN. It functions faster, since it is not dependent on another computer. It also has a bare-bones OS (microkernel) for processing I/O requests. Fault Tolerance and Power You need to protect your network from data loss due to power surges and failures. There are several tools on the market that will help prevent data loss from power fluctuations. In this case, the best tools seem to be the more expensive ones. The equipment described below is among the best available: UPS (Uninterruptible Power Supply) A UPS is battery powered, and guaranteed to provide power to a computer in the event of interruptions in the incoming electrical power. There are different types of UPS devices, and each type provides power for a different length of time. An Interactive UPS (also called an “intelligent UPS”) connects to the computer's serial port and provides information, such as battery time remaining, allowing the computer to shut down before complete loss of power. Surge Protectors Surge Protectors, also called surge suppressors, are power strips that provide protection from voltage spikes, surges, and sags in the power supply.

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Password Practices and Procedures A network administrator may encrypt password information that is automatically sent to the server when users log on to the network. Users working with sensitive information such as budgets, personnel records and other confidential data should change their passwords at least every 30 days. Policies that spell out password procedures should be given to all users so they will know what is expected of them. This holds users accountable for their actions on the network, and discourages them from wandering into unauthorized areas. The most effective passwords are ones that are the maximum number of characters and use a combination of letters, symbols, and numbers. Passwords should be changed more frequently in high-security networks. Some “classified” networks require password changes every day, but most networks can get by with changing their passwords every 30 days. So, an effective password policy is one in which passwords change on a regular basis, include characters, numbers and symbols, but are easy enough that users can remember them. Password security is compromised if a user writes his or her password down where it might be seen by others. The importance of users logging off and locking their workstations when they are not physically using them cannot be stressed enough. No one, no matter who they are, should be given the opportunity to look through another person’s desk while they are not there. If the network administrator needs to use the workstation, he or she will know how to accomplish the task. There is no reason for anyone other than the user to access the user’s files, so why make them available by not cleaning off your electronic desktop when you leave your workspace? Many large companies implement a “clean desk policy.” What this means is that if the employees leave their workstations (for any reason) they are required to clean off their desks or workstations and lock documents, etc. away. In order for this policy to be effective, management must randomly check to make sure that the policy is being applied. Evaluate your security policy on a regular basis to ensure that it is up to speed, and troubleshoot before the trouble starts. This is known as a security audit.

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Encryption Data can be encoded at the sender’s end and decoded at the recipient’s end so that no one, other than the person for whom the message was intended, can understand the message. This practice is called cryptography and the system is called a cryptosystem. Encryption converts regular text into ciphertext by combining the original data with one or more “keys” known only to the sender and recipient. These keys are numbers or strings of characters combined with the original text to create an algorithm. Encryption is used to scramble passwords on an internal network so that they may not be stolen during logon. It is also used to secure data over VPNs (Virtual Private Networks). A VPN is a network that uses the Internet to connect remote users to an internal network. Encryption is also used to encrypt E-mail transmissions, and is used extensively for online commerce (e-commerce) and online banking. Without encryption the Internet would be a hotbed for high-tech thieves who could tap into it and steal information and credit card numbers. Even with encryption, the Internet is not the most secure of environments. DES (Data Encryption Standard) is the fastest and easiest method of sending an encrypted message, because the sender and receiver use the same key to decrypt the data. DES was developed by IBM and is now the most commonly used Private Key encryption system used. This method uses a 56-bit private key. RSA is a public-key cryptosystem for both encryption and authentication. It was invented in 1977 by Ron Rivest, Adi Shamir, and Leonard Adleman. The name comes from their first initials. The entire security of RSA depends on the difficulty of factoring large prime numbers. RSA (Rivest-Shamir-Adleman) uses both a public key and a private key. The recipient’s public key is used by the sender to encrypt the message, and the recipient’s private key is used to decrypt it. 238

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Chapter 10 – Network Security Extra data appended to a message, which identifies and authenticates the sender and message data using public-key encryption, is called a digital signature. Public Key encryption uses the Diffie-Hellman algorithm and is a one-way type of encryption method. The sender encrypts the message using a public key and the receiver decrypts it using a private key. If the receiver wishes to respond, the message is encrypted using the original sender’s public key. The recipient of the response would then use their private key to decrypt the message. Symmetric Keys can also be used, but they are less secure. With this method of encryption both parties have the same key, which is used to encrypt data and to decrypt it. PGP (Pretty Good Privacy) is based on Public Key encryption and was developed to encrypt E-mail messages. As the name implies, it is not a completely secure encryption method. EES (Escrowed Encryption Standard) is known as skipjack and uses an 80-bit key. It is similar to DES, but the use of the 80-bit key makes it much more complex. Skipjack was originally designed to be integrated onto a chip known as a clipper chip. Disaster Recovery A disaster recovery plan (DRP) lays out how an organization or business is to deal with disasters. It is designed to offset or minimize the effect of a potential disaster on the business or organization. It should keep the mission-critical functions first and foremost, so as to allow the business or organization to quickly resume their activities. Prevention should also be addressed in the plan. Since the financial impact on a business can be severe if even down for an hour, much less a day, it is imperative that all possible disaster scenarios be addressed. Ensuring the integrity of your network infrastructure to the best of your ability, both on location and at backup sites, will ensure a much quicker recovery. Viruses Viruses are those nasty little programs that can wreak havoc on a computer and its data. There are over 60,000 known viruses. The sole purpose of a virus is to replicate and make life miserable for computer users. Many viruses are simple annoyances, but some of them can cause irreparable harm to files. Most viruses are written by hackers who are trying to show off. Viruses can be spread by various sources including: shareware, files downloaded from the Internet, software from unknown origins, and bulletin boards. There are four basic types of viruses: File Infectors: These attach themselves to executable files and spread to other files when the program is run. Boot Sector: These replace the master boot record (or boot sector on a floppy). They will write themselves into memory any time the computer is booted. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Trojan Horses: These appear to be legitimate programs, but when loaded, they will go to work on the system. Macro Virus: These attach themselves as executable code to documents and run when the document is opened. (They can also attach to some kinds of E-mail). It used to be true that you couldn’t get a virus from opening a document, just from running a program. Unfortunately while macros are very valuable, they mean that when you open a document you are running a program. Unfortunately viruses have become a way of life in the computer world. With this in mind, there are several measures you can take to prevent or at least minimize the damage: Purchase an antivirus program—there are several good ones on the market. Make sure it is compatible with all of the operating systems that you use. If the computer has a BIOS setting that allows you to disable boot-sector writes, (prevents applications from writing to the boot section of the hard disk), enable it! This setting must be disabled before installing a new operating system. Many viruses are transmitted by floppy disks. Be careful when reading floppies of unknown origin or using your disk on unfamiliar machines. These days, many viruses and macroviruses are transmitted over the Internet. Use extreme caution when you download files, especially if they come from sources other than a manufacturer’s Web site. The most secure protection against Internet-distributed viruses is to make sure you have an antivirus program running at all times (or at least when you’re downloading and first running new files). Trust no one when it comes to loading programs on your machine. Keep your anti-virus program updated. Hundreds of viruses are written each month.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book. Keyword Data Encryption Differential Backup Disaster Recovery Disk Mirroring Disk Striping Firewall Full Backup Incremental Backup NAS Password Security RAID SAN Share Level Security User Level Security Volumes

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Chapter 10 – Network Security

Review Questions Chapter 10 1. What are the two requirements of user level logon? 2. In a share level model, passwords are assigned to __________.

3. What is the function of a firewall?

4. The acronym RAID stands for __________.

5. What are the three common levels of RAID?

6. What purpose does encryption play in your security model?

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Conclusion

Chapter 11 – Troubleshooting a Network Being a computer and network professional automatically implies that you are a troubleshooter. If fact, troubleshooting comprises perhaps the single largest aspect of working with computer and network hardware and software. After all, if you are the expert, you will most likely be called when there is a problem, not when all is well. The majority of this course has focused on the facts and science of networks. This chapter will focus on the application of these facts to solve problems. Being an effective troubleshooter does not come automatically with networking knowledge (even though it is implied). Troubleshooting is an art and can be learned. What you must learn is how to approach a problem in an organized and methodical manner. This chapter will begin with some basic troubleshooting techniques, and progress with some specific tools that you can employ to simplify the process.

Basic Troubleshooting As mentioned, troubleshooting is more of an art form than a science. For some technicians troubleshooting comes naturally, while for others it is a struggle. For those who must endure the struggle, a habit of applying a methodical and determined approach will soon result in it becoming second nature for you. Let’s take a look at an eight-part approach that will lead to successful troubleshooting. The eight parts are as follows: establish the symptoms, identify the affected area, establish what has changed, select the most probable cause, implement a solution, test the result, recognize the potential effects of the solution and document the solution. It is proper use of all the parts that will make your next troubleshooting exercise easier. Establish the symptoms: Defining a problem is not always as simple as it sounds. In most cases, it seems well defined by the person who calls and complains! But is it really defined? Frequently the problem, “as reported,” is really just the symptom and not the true cause. To make matters worse, computers never fail at a convenient time. They always fail in the middle of a job, or when there is a deadline and the user must have it fixed now. This added frustration often leads to confusion and stress. Remember, you are looking for the cause, not the symptom. As a troubleshooter, you must be able to quickly and confidently eliminate as many alternatives as possible, so that you can focus on the things that might be the cause of the problem. In order to do this, you must be organized. The first step is the most critical and often the most ignored. Without a complete understanding of the problem (the entire problem) you can spend a great deal of time working on the symptoms instead of the cause. The only tools required for this phase are a pad of paper, a pen (or pencil), and good listening skills. Be sure to listen carefully to your client or co-worker. The user of the computer or network is your best source of information. Don’t assume that just because you are the expert, the operator doesn’t know what caused the problem. They may not know the technical reason for the failure, but they often hold the keys to the problem. Remember, Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide you may know how the computer and network runs and can find the technical cause of the failure, but the operator was there before (and after) the problem started and may recall the events that led up to the failure. You may, however, have to ask some specific questions to jog their memory, or help them focus on what was going on when the problem first occurred. Do not make the questions too technical, and most importantly, do not intimidate the user. Ask a few questions to help identify the problem and list the events as they occurred before the failure. You may want to create a form with these questions (and others specific to the situation) for taking notes: When did you first notice the problem? What has changed since the computer was last used? (New Software, network or computer moved, recent software upgrade.) Show me how to create the error. Describe any changes in the computer (noise, screen changes, lights, and so forth). Are you the only one having the problem? Did anyone else use this computer? The list of questions could go on forever. You will need to create your own list based on the situation. With a little experience, you will be able to identify the best questions for the situation. Identify the affected area The next step involves the process of isolating the problem. Isolating the problem is the art of eliminating what you know from what you don’t know. For example, if a keyboard is not working and you connect a known good keyboard to the computer and it works, you have isolated the problem to the keyboard or its cabling. There is no particular approach to follow and there is no substitute for experience. The best you can do is to eliminate any obvious problem and work toward the more complex. The purpose is to narrow the search down to one or two general categories. Be sure to observe the failure yourself. If possible, have someone demonstrate the failure to you. If it is an operatorinduced problem, it is important to observe how it is created, as well as the results. Establish what has changed The most difficult problems to isolate are the intermittent ones. These never seem to occur when you are present. The only way to resolve these is to be able to re-create the set of circumstances that caused the failure. Sometimes, the process of elimination is all that you can do. This will take time and patience. The user will need to keep detailed records of what is being done before, and when, the failure occurs. One thing that might

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Conclusion help in such cases is to tell the user to not do anything with the computer when the problem recurs, but to call you. That way the “evidence” is not disturbed. Isolation of a problem requires a structured approach. It requires two simple steps, make a plan and follow it. Select the most probable cause Make a Plan and Follow it from Beginning to End Create a planned approach to isolate the problem based on your knowledge at this point. Start with the most obvious or easiest solution to eliminate, and move forward. Write down your plan! The first step of any plan should be document and back up. Do not make any assumptions. If you must make any assumptions, write them down. You may have to refer back to them later. Once a plan is created, it is important to follow it through. Jumping around and randomly trying things can often lead to more serious problems. Document every action and its results. If the first plan is not successful (it won’t always be), create a new plan based on what you discovered with the previous plan. Be sure to refer to any assumptions you may have made. In the case of a network problem, the first step in isolation is to separate a network (hardware) problem from a workstation problem. For example, is the problem occurring on more than one workstation or is it only on one? If you determine that the problem is only on one workstation and the cabling and network card are working properly, then you need to further isolate the problem to determine which program is experiencing difficulty. If for example, you can “see” other computers in the network neighborhood, but you cannot receive any E-mail, then you know for sure that the network is physically working, but something must be wrong in the E-mail software or configuration. The general procedure for isolating network problems is to start globally and work to locally. Starting from the top, isolate the problem to: A WAN or LAN A segment of a LAN A workgroup or domain A server or workstation A workstation or user

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Network + Training & Test Preparation Guide Once the search has been narrowed, start looking for specific hardware: Routers Hubs/Concentrator Cabling or Connections Adapters Software related problems could also be isolated to several causes: Protocols Authentications As often as not, the problem may be caused by the operator, and not the hardware or the system. In these cases, you must be careful as to how you resolve the problem while not alienating the operator. Frustrated and confused operators can lead to further problems. Here are a few suggestions for isolating the hardware/software from the operator: Have another operator perform the same task on their own workstation, as well as the one that is causing problems. It is important to use another operator. This will keep you removed from the problem and eliminate the “it always works for the expert” syndrome. Confirm that the operator is using standard operating procedures. This means to have the operator duplicate the problem while you watch – do not tell them how. Implement a solution After locating or at least narrowing the problem to a few possibilities, either repair or replace the defect. With hardware, repair or replacement is usually all that is needed. However, if the problem is software or configuration related, it may require some additional effort. To resolve these types of problems, you must do three things: Formulate a correction (write down what you think will resolve the problem). Test the correction (make sure that the changes work). Implement the solution. Note: If the problem is software-oriented, be sure to record the “before” and “after” changes. Resolving operator-induced failures is more difficult than hardware induced failures. In these situations, you must be very careful to treat the cause and not the symptoms. For example, if an operator is afraid of computers in general, no amount of training or instruction will solve a problem until that general fear is removed.

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Conclusion Now we want to separate the true professional from the amateur. Many troubleshooting and repair services operate on the fix and run principle. The basis for this policy is that once the system is running, you are wasting your time and should be working on the next problem. The reality is that the time you spend after the repair can save repeat service calls and shorten the time-cycle for future service calls. Test the Result No repair is complete without confirmation that the job is done. Confirmation means to make sure that the problem no longer exists. Ask the user to test the solution and confirm satisfaction. Recognize the potential effects of the solution Make sure that the fix did not create other problems. You have not done a professional job if the repair was completed at the expense of something else. Confirmation of the repair can save you a return trip to repeat the fix or to correct a problem that you created. Confirming the repair may include some form of feedback from the user, or a follow up call just to make sure all is well. Document the solution Finally, document the problem and the repair. This means to document (in writing) the symptoms, the problem, and the repair. In troubleshooting, there is no substitute for experience. You must look at every new problem as an opportunity to expand that experience. Keeping a copy of the repair procedure in your technical library may come in handy in a year or two when the problem (or one like it) happens again. This is one way to build, maintain, and share experience.

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Networking and Troubleshooting Tools Just like a good computer repair technician, a network troubleshooter will need a few tools to make the process of troubleshooting easier. Networking tools can be divided into two categories: hardware tools and software tools. Hardware Networking Tools Before we get into the tools that are designed specifically to troubleshoot and ensure the integrity of your network, let us quickly cover some tools used to setup the network cabling. Wire Crimper The wire crimper is a versatile tool that strips and cuts copper wire as well as crimping solderless terminals. The narrow nose with its serrated jaws is used for pulling or coiling wire.

Punch Down Tool Punch down tools are used to “punch down” cabling to “blocks” in your wiring rack. They secure the connection between the wires and the block.

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Conclusion Hardware Troubleshooting Tools Hardware troubleshooting tools are used to confirm the integrity of the cabling. Network cabling is, in principle, very easy to troubleshoot. Since it is made up of wires, you can have only one of two problems. A good cable will provide continuity or current flow from one end to the other. A bad cable will be either open or shorted. An open conductor means that the cable is broken and the current will not flow from one end to the other. A shorted conductor means that the current is flowing to ground or another cable instead of being isolated. These failures are like a water pipe that is broken (open) or has a leak (shorted). There are several tools we can use to check for open and shorted wires. We will start by looking at a multimeter, which is one of the most basic tools for electronic troubleshooting. The Multimeter The name multimeter was derived from its ability to measure several different parameters. You can test for AC and DC voltage, resistance, and continuity. Some meters will let you test for current as well, but only low amounts (less than 10 amps). With it you can test various electronic components, as well as the electrical power in the computer. Most will consist of a digital or analog meter or display, a pair of wires with probes (one black and one red), and a switch for adjusting the range of settings to be measured. The red wire is the positive probe and the black wire is the negative or ground probe. When working with network cabling, we will have to know how to test for continuity. The purpose of continuity testing is to confirm a complete electrical circuit. For example, it is to check to see that a wire is not broken. Most multimeters have a “continuity” setting, which will indicate a complete circuit by either a light or a sound. When you connect both leads of the meter to each end of the device you are testing, a positive test (the light comes on or it makes a noise) means that the circuit is complete. If the test is negative (no light or noise), the circuit is broken. If your meter does not have a continuity setting, it is still possible to test for continuity. All you need to do is use the resistance setting and test the device. In a wire for example, the resistance reading for continuity would be zero – meaning that current is flowing without resistance. If the wire is broken, the resistance reading will be infinity or maximum – meaning that no current is flowing. Media Tester Media testers are usually devices used to test the cabling, whether it be RJ-11 or RJ-45. They can check for continuity and how the pin outs line up. These devices are generally used when you make your own cabling.

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Tone Generator and Tone Locator A multimeter is a universal tool and almost any electrical or electronic technician should have one. The problem when using this tool for testing continuity of a network cable is the length of the cable. If both ends are in the same location, this is not a problem. However, if the cable is a hundred feet long and spans the length of a building, testing for continuity will require an additional wire. You can use a pair of wires (very common in network cables) and connect the two wires at one end, and test at the other end. However, there are more often than not, several pairs of wires at one end (the hub or patch panel). The question then becomes which pair goes to which room? Solving these problems with continuity testing can take a long time unless you are just lucky. Telephone and phone wiring companies use two tools, called tone generators and tone locators, to find pairs of wires in a bundle. The tone generator is connected to the wires at the known location (the room with the outlet). This applies a signal on the wires. The tone locator is a receiver that is set to the frequency of the generator. When the receiver is placed in close proximity to the wire that has the signal applied, it will emit a tone, thus locating the wires. When used together, these tools are often called a fox and a hound.

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Conclusion

Test Cables One method of isolating problems is to use a special cable to remove a workstation from a network and simulate that it is still connected. Two such cables are the hardware loopback and the crossover cable. A loopback cable is just what the name implies. It is a single-ended cable that connects to a network card. It has the transmit and receive wires connected. Any signal placed on the transmit wire will loopback to the receive wire, and therefore back to the network card. If you are able to send a signal and have it return, you will know that the network card and the protocol stack are functioning. A crossover cable is similar to a loopback, but is double-ended. The transmit wire on one connector is connected to the receive wire on the other (and vice versa). These cables can be used to connect two computers into a single network eliminating any other network hardware. Be careful when using a crossover cable, because they look just like patch cables but are not interchangeable. Time Domain Reflectometer For those who are serious network troubleshooters, there are advanced tools that may well be worth the time and investment. The Time-Domain Reflectometer (TDR) is used to find breaks and shorts in network cabling. By calculating the time it takes a signal to travel the length of a cable and to be reflected back, the location of any break or short can be determined. Protocol Analyzer A protocol analyzer is used to monitor and analyze network traffic. Software analyzers, also called packet sniffers, are usually a PC with a special network card. They will monitor network traffic, capture packets and generate reports. Many protocol analyzers will include a TDR as one of their functions.

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Network + Training & Test Preparation Guide Optical Tester Optical Testers or optical time domain reflectometers (OTDR) are essentially the same as a TDR, but used for fiber optic cabling. OTDRs also calculate the locations of breaks by the amount of time it takes for a signal to travel the length of the cable and back.

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Conclusion

Maintaining and Troubleshooting Networks Maintaining and troubleshooting networks differs from operating system to operating system. Therefore, you will need to refer to the operating systems’ manuals for detailed troubleshooting procedures. The following table provides some generic troubleshooting concepts:

Situation

Probable Cause

A single workstation does not connect to the network.

Usually these are authentication errors, but can be caused by a disconnected cable.

Authentication

A common failure is for a user to be unable to logon. Often these are caused by typos when entering user names and passwords. Some passwords are case-sensitive, and a stuck caps-lock key can cause errors.

Common Mode Failures

Common mode failures are generated when one component of a LAN causes the entire LAN to fail. An example would be a network card that begins to continually broadcast useless information and overloads the network. This is sometimes called a broadcast storm.

Loss of Data

If data transfers are incomplete or inaccurate, check to ensure all network cabling and connectors are intact.

Network Security Violations (Insufficient Rights or Permissions)

Anything that breaks the integrity of the data on a network is a break of security. You can’t access a resource unless the administrator of the network has allowed you to do so.

Reduced Bandwidth

Reduced bandwidth is just like a traffic jam. For some reason, the traffic is not moving, due to either excessive traffic or a bottleneck. A bottleneck is any resource that limits the rate at which network traffic can be moved. It could be the processor, the network, or a disk resource.

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Slow Loading of Programs and Files

Fragmentation occurs when the operating system saves, deletes, and moves information. You must defragment the drive. If slow loading persists even after defragmenting, check for memory bottlenecks.

Traffic Overloads

As networks grow, so does the traffic. When the amount of traffic exceeds the ability of the network to carry it, the network slows down. These problems can be addressed by segmenting the network and scheduling non-critical work for after hours. For example, tasks like backing up drives or moving large amounts of data can be done at night.

Unauthorized Software

You must manage software distribution to ensure users are not loading non-licensed software and computer viruses onto the network drives.

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Conclusion

Troubleshooting Scenarios The following summarizes some possible scenarios that you may encounter and how to provide a solution: Misbehaving Protocols You have just installed a new workstation and are unable to see any other workstations or servers on the network. If you are using TCP/IP, you can confirm your hardware and protocols by using the IPCONFIG, PING, and TRACERT commands to test the network. These commands work from a command prompt. TRACERT allows you to trace the “hops’ (routers encountered) that a packet takes to its destination. It also lets you know the time that it takes. This comes in handy if you need to see where exactly on your intranet or on the Internet your packet is going. The first step is to PING the loopback address. This will test the protocol stack in the computer. The loopback address is 127.0.0.1. Remember this address, because as a network professional, you will use it often.

The next step is to use IPCONFIG to get details about your workstation. On a Windows 95/98 computer, you can use the WINIPCFG command from the RUN dialog box in the START menu. This command will give the same results as IPCONFIG from DOS, but looks better and includes the MAC address of the network adapter card. On a Macintosh system, open the TCP/IP Control Panel to use these utilities.

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Notice that the IP address of this computer is 195.55.48.6. If you are using Windows, WINIPCFG, your dialog box will look like the following. This command is only for Windows 9x and ME and will not work on a Windows NT, 2000, XP, or 2003 system.

You can now PING that address to determine if the network card and protocol stack for the computer are working properly.

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Conclusion

Continue the process by PINGing another workstation, the server, and so on. With each step, you will be testing a larger portion of the network. If at any stage, you receive a message like the following, you have encountered a problem.

If you are unable to reach a host computer, then there is a problem with the protocol. Usually this means you have the wrong IP address, or the computer you are PINGing is not using the TCP/IP protocol. It could simply mean that it is not logged on to the network. For the IPX/SPX networks, use the ipxping command. Cable Problems Cabling problems are simple: either they work or they don’t. The biggest problem with them is that we often assume that since they worked yesterday, they must be okay. Poor connections and loose connectors cause most cable problems. Here are some suggestions when you suspect cable problems: Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Any time a computer was moved and it suddenly stops responding to the network, suspect a loose or disconnected cable. Replace any suspect drop or patch cables with a known good one. Check the indicator lights on the adapter card. If present, they will let you know if the card is working and if it can access the network. NIC Indicator Lights Many network cards have from one to three LED lights (green or yellow) next to the cable connector. These lights can be seen from the back of the computer. The actual function of each light will depend on the manufacturer and you may have to check the documentation that came with the card for details. In general, they will indicate whether or not the card can detect the presence of a network and when data is being transmitted. If no lights are on, you can be sure that the network is not being detected, while green lights indicate that all is well. Name Resolution You are testing a new workstation and are unable to see the workstation by its domain name. You know that the IP connection is good because you can PING the IP address. How do you determine the problem? One network problem encountered is name resolution. Earlier, we learned that workstations, or hosts, have two names. One is the IP address number, (which the computers like) and the other is the IP address name (which we humans like). Somewhere in the system is a table or database that provides the translations from number to name and vise versa. That location is the DNS (Domain Name Server). To resolve this problem, you will need to use a TCP/IP utility called “nslookup.” With nslookup, you can connect directly to the DNS and access the information stored there. Another place to look for name resolution problems (on a local LAN) is in the HOSTS and LMHOSTS files. These are text files that are used to statically map local and remote hostnames and NetBIOS names to IP addresses, respectively. If these files are being used, you can find them on the host in the systemroot\system32\driver directory. The difference between HOSTS and LMHOSTS is that HOSTS is used in place of DNS and LMHOSTS is used in place of WINS. Performance You think that your network is performing without problems, but are starting to get complaints that “the network is slow.” What are you going to do? These problems are often difficult to resolve because there are a vast number of possibilities as to the cause. If there is a sudden change in performance, the first thing to do is find out what has changed. Any new hardware or applications (including upgrades) are always good candidates for the problem. Beyond that, we need to look at four limiting factors on performance.

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Conclusion Bandwidth and Throughput Bandwidth and throughput are not the same thing, but are interrelated. You can think of a network as a super highway and the vehicles as being packets of information. The speed limit, or maximum speed that traffic can move, is the throughput and is measured in Mbps (Megabits per second). The bandwidth is the number of packets that can move past a point at any given time (also measured in Mbps). Think of the bandwidth as the number of lanes on the highway (the more lanes, the more packets that can be moved). Just like our highway, if the traffic gets too congested, everything slows down. The performance of a network will only be as fast as the slowest link in the entire system. Therefore, if any one component is performing poorly, it will affect the entire network. Latency Small delays in packet movement that are caused by devices is called latency. Routers and switches that connect any two segments of a network can cause these delays. Latency delays, for the most part, are negligible, but can be measured and will affect performance in large networks. Application Efficiency Any application that was not designed to work over a network will be unable to take full advantage of network protocols. This can slow down data transfer. For example, some network operating systems will allow for burst mode operation. This means that for a small amount of time, it can send data at a faster than rated speed. An application will have to be designed to take advantage of burst mode in order to use it. Server/Workstation Limits Nothing will slow down a network more than a sluggish server. A server that is operating its CPU at 100% will have to delay processing of each request until it completes its current request. This may require the requestor to continue to resend its request, adding to the network load. A server with a memory deficiency will have to write information to a disk cache. Reading and writing from a disk is much slower than from memory. Resolving performance problems can be easy, after you identify the problem. The trick is knowing how the network performed when it was good and how it performs now. The answer lies in creating a performance baseline. A baseline is simply a record of performance criteria at a given time. To create a baseline, you will need to run a series of tests and record the performance. For example, if you are experiencing slow printing, you can print the same document at different times throughout the day and record the time it takes to print. From this information, you will know the high, slow, and average time to print the document. Then, at a later date, you can re-test the printer performance under the same conditions and determine if things have changed. Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide The key to monitoring network performance is statistics. Network statistics will come from two sources – the server and the network. To collect these statistics, you will need to use some software called performance monitor for the server or network statistics software for the network itself. Windows has a built in performance monitor as part of its administrative tools. With this activated, you can monitor and collect data for a variety of events. With this tool, you will be able to monitor such events as processor time, available memory, etc. Similar software packages (usually as part of a network analyzer) will collect data for packets/sec, percent of network utilization, etc.

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KEYWORDS Exercise Define each of the following keywords. Hint: There’s a glossary in the back of this book. Keyword

Definition

Bandwidth IPCONFIG Latency Media Tester Multimeter Performance Monitor PING Punch Down Tool TDR Throughput Tone Generator Tone Locator WINIPCFG Wire Crimper

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Review Questions Chapter 11 1. What are the three primary steps to take when troubleshooting? 2. After repairing a problem, are you finished with the troubleshooting process?

3. You are troubleshooting a cable problem. You have found the cabinet with the patch panel and hub, but need to know which of the 50 cables goes to the accounting office. What would be the best tool to help you locate the cable in question?

4. You have located the cable in question #3, and think it might be shorted. What tool would you need to find the short?

5. You are working with a TCP/IP network and want to confirm the protocol stack in a specific workstation. What utility can you use to confirm that the protocol stack is good?

6. What is the loopback IP address?

7. You need to know the IP address of a workstation. What TCP/IP utility can you use to find the IP address of the workstation? 8. You have just connected a workstation to the network. What is the easiest way to tell if the network card can “see” the network? 9. What is the difference between bandwidth and throughput?

10. You have a Windows 2000 network and received complaints that the server is running slowly. What utility can you use to determine the performance of the server?

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Conclusion This concludes our Network+ Training & Test Preparation guide. We hope that you have enjoyed your Network+ training journey as much as we have enjoyed providing it to you. Remember, the best thing about a self-study course is that you are able to review it as much, and as often, as you like. To measure your retention of these materials, start taking the practice exams that are on the CD-ROM that was included with this course. After taking a practice exam, be sure to review any areas that need improvement. When you are consistently achieving scores in the 90% range, you are ready to sit for your certification exam. The following “Appendix A” is an excellent source of review material, and don’t forget to use the Glossary. When you are ready to schedule your exam, be sure to refer back to the beginning of this book for tips on what to expect at the exam site. We love to hear from our students, so if you have any questions, or if you just want to let us know how you are doing, we’d be happy to hear from you! Remember, at Specialized Solutions, our success is directly tied to the success that our students have with our training and certification products. Thank you for allowing us to be your training partner and please let us know if we can help with any of your future training needs.

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Appendix A – Tech Summary

Appendix A – Tech Summary The following tables summarize key information found in this course:

5-4-3 Rule When installing coaxial Ethernet cabling, you must conform to the 5-4-3 rule. •

Maximum of 5 segments in a series.

•

Maximum of 4 repeaters.

•

Only 3 segments can contain nodes.

Coaxial Cable Types Not all coaxial cables are the same. They are specified based on their impedance. Impedance is a unit of measurement for resistance to AC voltages. It is expressed in ohms. In order for the network to operate at peak performance, all electronic components must operate at the same impedance. Using the wrong cable will cause poor performance and/or failure of the network.

Uses

Type

Impedance – Ohms

10Base5 Thicknet

RG-8

50

10Base5 Thicknet

RG-11

50

10Base2 Thinnet

RG-58

50

Cable TV

RG-59

75

ARCnet

RG-62

93

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RG-58 /U

Solid copper core.

RG-58 A/U

Stranded wire core.

RG-58 C/U

Military specification of RG-58 A/U.

RG-59

Broadband transmission, such as cable television.

RG-6

Larger in diameter and rated for higher frequencies than RG-59, but also used for broadband transmissions.

RG-62

ArcNet networks.

Ethernet Cabling

Cable Type

Topology

Max. Length (meters)

Speed Mbps

Nodes Per Segment

Max Segments

Max. Repeaters

Max Segments with Nodes

10Base5

Coaxial Thicknet

Bus

500

10

100

5

4

3

10Base2

Coaxial Thinnet

Bus

185

10

30

5

4

3

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Appendix A – Tech Summary

UTP Cable Categories

Category

Wire Specs

Uses

1&2

Suitable only below 4 Mbps.

Voice ONLY

3

Four twisted pairs with three twists per inch.

10 Mbps

4

Four twisted pairs with 4 twists per inch.

Data grade up to 16 Mbps.

5

Four twisted pairs with 5 twists per inch.

Data grade up to 100 Mbps.

IBM Cable Types (Token Ring) IBM has created its own standards for their Token Ring Networks. Type

Wire Specs

Uses

1

Two STP solid core 22 AWG wires – maximum length 101 meters (331 feet).

Connect between terminals and distribution boxes or between different wiring closets.

2

Six twisted pairs, two STP and four UTP – maximum length 100 meters (328 feet).

Same as type 1, but adds voice capability along with data.

3

Four UTP with two twists per inch – 22 or 24 AWG wire –maximum cable length is 45 meters (148 feet).

Lower cost alternative to type 1 or 2. Cannot be used for 16 Mbps Token Ring. Voice-grade cable.

4

Not Defined

5

Two 62.5/125-micron multi-mode fibers.

Fiber Optic

6

Two STP – 26 AWG wire.

Data patch cables.

7

Not Defined

8

Two STP – 26 AWG.

Contains a shield for use under carpets.

9

Two STP –26 AWG wire.

Plenum grade. Specialized Solutions, Inc.

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IEEE 802.x Standards The IEEE 802 standards work in the Physical and Data Link layers of the OSI Model. They also divide the Data Link Layer into two sub-layers: Logical Link Control and Media Access Controls.

802.x Standard

270

Basis of Standard

802.1

Internetworking

802.2

Logical Link Control Sub Layer

802.3

CSMA/CD Ethernet

802.4

Token Bus LAN

802.5

Token Ring LAN

802.6

Metropolitan Area Networks (MAN)

802.7

Broadband Technologies

802.8

Fiber Optic Technologies

802.9

Hybrid Voice/Data Networks

802.10

Network Security

802.11

Wireless Networks

802.12

High Speed LANs

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Appendix A – Tech Summary

IRQ Assignments IRQ assignments can vary from computer to computer; however, there are some that are always the same and some that can be changed. The following is a standard configuration for IRQ settings: IRQ

Function

Available for Change

0

System Timer

No

1

Keyboard Controller

No

Available

Yes

2/9 3

COM2, COM4

Usually

4

COM1, COM3

Usually

5

LPT2

6

Floppy Controller

7

LPT1

8

Real-time Clock

No

10

Available

Yes

11

SCSI/available

Yes

12

Available

Yes

13

Math Coprocessor

14

Primary IDE

15

Secondary IDE

Usually-Often used for NICs. No Usually

If no math coprocessor No Usually

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Network + Training & Test Preparation Guide In addition to IRQs you may have to set the Base I/O address. The following are common address assignments: 200 to 20F – Game Port 210 to 21F 220 to22F 230 to 23F – Bus Mouse 240 to 24F 260 to 26F 270 to 27F - LPT3 280 to 28F 290 to 29F 2A0 to 2AF 2B0 to 2BF 2C0 to 2CF 2D0 to 2DF 2E0 to 2EF – COM2 300 to 30F – Network Adapter Card 310 to 31F – Network Adapter Card 320 to 32F – Hard Disk Controller (For PS/2 Model 30) 330 to 33F 340 to 34F 350 to 35F 360 to 36F 370 to 37F - LPT2 380 to 38F 390 to 39F 272

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Appendix A – Tech Summary 3A0 to 3AF 3B0 to 3BF – LPT1 3C0 to 3CF – EGA/VGA 3D0 to 3DF – CGA/MCGA (also EGA/VGA in color video Modes) 3E0 to 3EF 3F0 to 3FF – Floppy Disk Controller

OSI Model

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Network + Training & Test Preparation Guide OSI Model and Connectivity Devices: Layer Number

Name

7

Application

6

Presentation

Devices Computers Gateways

5

Session

4

Transport

3

Network

Routers Brouter

2

Data Link

Bridges

1

Physical

NICs, Hubs, Repeaters

Switches

Subnet Masking Subnet masks are used to divide an IP address into its network address and host address. Subnet masks are assigned according to the following three classes:

Class

274

IP Address

Default Subnet Mask

A

001.x.x.x to 126.x.x.x

255.0.0.0

B

128.x.x.x to 191. x.x.x

255.255.0.0

C

192.x.x.x to 223. x.x.x

255.255.255.0

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Number of Networks

Number of Host

126

16,777,214

16,384

65,534

2,097,152

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TCP/IP Ports A port is a virtual outlet that can be opened on a network device. Common ports are as follows:

Service

Port

FTP

21

TELNET

23

SMTP

25

HTTP

80

POP3

110

TCP/IP Utilities TCP/IP provides many tools for troubleshooting networks. Here are some command-line utilities:

IFCONFIG

Shows the Linux user’s network interface configuration.

IPCONFIG

Displays the basic local host configuration – IP address, the subnet address, the subnet mask, and default gateway.

PING

Sends a test packet to a specified address. If all is well, it will return. Use the loopback address (127.0.0.1) to test the IP architecture and configuration.

ARP

Used to see the entries in the Address Resolution table (uses IP addresses to find MAC addresses).

RARP

Uses a MAC address to find an IP address.

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ROUTE

Used to see the local routing table and to add entries to it. Use ROUTE PRINT to display contents, ROUTE ADD to add entries and ROUTE DELETE to remove entries.

NBSTAT

Used to check the resolution of NetBIOS names to TCP/IP addresses.

NETSTAT

Used to check the status of current IP connections.

TRACERT

Used to verify the route to a remote host. (Pronounced Trace Route.)

NSLOOKUP

Used to verify entries on a DNS server.

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Transmission Media Media

Bandwidth (Mbps)

Nodes/Segment

Maximum Nodes per Network

Maximum Cable Length (meters)

UTP

4-100

1

1024

100

STP

16-155

Varies

260

100

Coaxial Thicknet

10

100

300

500

Coaxial Thinnet

10

30

90

185

Fiber Optic

2000

1

1024

2000

Infrared

1-10

NA

Varies

32

Troubleshooting Tools

Hardware

278

Uses

Volt/Ohm Meter

Used to test voltages, resistance, and continuity of electronic devices and circuitry.

Cable Tester

TDR – checks and locates breaks in cables.

Oscilloscope

An electronic device that graphically displays frequency and magnitude of analog signals. Can also be used for precise voltage measurements. Used with TDR to locate cable breaks.

Protocol Analyzer

Also called a network analyzer. Used to capture packets on a network and analyze them.

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Appendix A – Tech Summary

Software

Uses

Performance Monitor

Use to monitor and graphically display various performance parameters found on workstations, servers, and networks. Used to provide information for network baselines.

Event Viewer

Displays or prints a list of events.

SNMP

Simple Network Management Protocol – used to monitor network devices (servers, hubs, interface cards, routers, and bridges).

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Appendix B – Useful Web Sites

Appendix B – Useful Web Sites Microsoft: http://www.microsoft.com

Novell http://www.novell.com

Other Helpful Sites http://www.cnet.com

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Appendix C – Network Standards Organizations

Appendix C – Network Standards Organizations The networking industry is full of standards and committees making new standards. This appendix will summarize several of the important standards used in the network industry. For additional information, search for these organizations on the Internet.

ANSI This is one of the most common standards in the computing industry, let alone the networking industry. The American National Standards Institute (ANSI) is an organization of industry and business groups who develop trade and communication standards. In the computing industry, it is perhaps best known for the development of the ASCII character set. This is a common code for basic characters and numbers. ANSI also is the United States representative on several international organizations like ISO and CCITT (see below).

CCITT The CCITT (Comité Consultatif Internationale de Télégraphie et Téléphonie) is an international organization also known as the International Telegraph and Telephone Consultative Committee. As its name implies, it is responsible for establishing standards for communication. Perhaps the most famous standards are the “V” standards for modems and Faxes.

EIA The Electronics Industries Association (EIA) is a group of American manufacturers of electronic equipment. It is prominent in developing standards for the interface between data processing equipment and communication equipment. Perhaps the most well known standard is the RS-232 standard for serial communication via DB-9 and DB-25 connector.

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IEEE The IEEE (Institute of Electrical and Electronic Engineers, Inc.) publishes many standards for electrical and electronic equipment. Since they cover a wide variety of equipment, the IEEE is subdivided into committees. The one that is important to networking professionals is called the IEEE 802.x committee. These standards are used for equipment operating in the Physical and Data link layers of the OSI Model. See Appendix A for a summary of the 802.x sub-committees.

ISO The International Standards Organization (ISO) is responsible for establishing international standards for all services and manufactured product. A major ISO contribution to the network community was the development of the OSI (Open System Interconnection) model. Be careful to not get ISO and OSI confused.

SAG SAG or SQL Access Group is working in conjunction with ISO to develop interoperability standards. As you may guess from its name, its emphasis is on SQL or the Structured Query Language. This is a common platform for transferring data from one database application to another. As long as both are SQL compliant, the data can be smoothly transferred.

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Appendix D – How to Register for the Exam

Appendix D – How to Register for the Exam

To Register for the Network+ Exams Register for the Network+ Certification Exam by calling 1-888-895-6116 for Prometric or 1-877-551-7587 for VUE. Tests are given at both Prometric and VUE Authorized Testing Centers. To register via the Internet, go to www.2test.com for Prometric or www.vue.com for VUE.

When you call, please have the following available: Social Security Number or Testing ID Two forms of ID (one with photo) Mailing address and telephone number. Date you wish to take the test. Method of payment, credit card or voucher. The test is available to anyone who wants to take the test. Payment is made at the time of registration, either by credit card, or by requesting an invoice be sent to you or your employer. Vouchers and coupons are also redeemed at this time. Individuals may retake the test as often as they like. Payment must be made each time you take the test. Prices subject to change without notice, and may be obtained by calling Prometric or VUE.

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Appendix E – Glossary

Appendix E – Glossary Access Method

A way of accessing the network.

ACK

Acknowledgment message confirming receipt of the data packet.

Active Hub

Regenerates or amplifies a signal when it is passed through.

Analog Signal

A continuously variable signal, or a circuit or device designed to handle such signals; opposite of digital.

AppleShare

The file server on an AppleTalk network.

AppleTalk

The Apple networking protocol.

Application

Software, program; these three terms are often used interchangeably.

Application Layer

The highest layer of the OSI Model, it supplies functions to applications, or computers on the network (nodes), so they can communicate with other applications or nodes.

Application Server

A dedicated server for applications.

ARCNet

Attached Resource Computer Network

ARP

Address Resolution Protocol

Attenuation

The signal loss due to the physical properties of copper wire that happens over distance.

AWG

American Wire Gauge AWG is the standard that describes wire thickness. The AWG wire number decreases as the wire thickness increases.

Bandwidth

The difference between the lowest and highest transmission channel frequencies, usually expressed in cycles per second (Hertz or Hz), or bits per second (bps).

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Base I/O Port Address

The channel through which data flows between a computer’s hardware (such as a NIC) and the CPU.

Base Memory Address

The location in a computer’s RAM of the beginning of the buffer area that is reserved for use by the NIC.

Baseband

Uses the entire capacity of the cable as a single channel.

Beaconing

A process used to identify any area on the network that may be experiencing problems.

BNC Connector

British Naval Connector

BOOTP

BOOTstrap Protocol

Boot Prom

Boot Programmable Read Only Memory is used on networks that utilize diskless workstations.

Bridge

Hardware that connects one network with another.

Broadband

Broadband allows two or more channels to share the bandwidth of the cable or medium. The signal flow is uni-directional.

Buffer

A bus driver. Can also refer to a class of memory registers and devices that match data transfer speeds between computers and hardware (peripherals). An area of memory that holds information for a peripheral device until it can be processed.

Bus Topology

A LAN in which all workstations are connected to a single cable.

Carrier

Companies contracted to carry our data over long distances.

Cellular Networking

A form of mobile computing.

Class A IP Address

IP Address used by very large networks, such as IBM, GM, or DEC.

Class B IP Address

IP Address used by medium-sized networks, such as Microsoft; these are all in use at the present time.

Class C IP Address

Class C IP addresses are used for smaller networks that do not exceed 254 hosts.

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Appendix E – Glossary Client

User computer “being served” by another computer, called a server.

Client Software

Software used by the client.

Clocking

The method used by the NIC to count and pace the number of signals that it sends and receives.

Coaxial Cable

An electrical cable consisting of a solid piece of metal wire surrounded by insulation, which is, itself, surrounded by a tubular piece of plastic.

Concentrator

Same as a hub.

Cooperative Multitasking

A form of multitasking, in which it is the responsibility of the currently running task to give up the processor, to allow other tasks to run.

CRC

Cyclic Redundancy Check, or Cyclic redundancy Code, is a number derived from, stored, or transmitted with a group of data in order to detect data corruption.

Crosstalk

The signal bleed that occurs between individual wires in a cable.

CSMA/CA

Carrier Sense Multiple Access with Collision Avoidance

CSMA/CD

Carrier Sense Multiple Access with Collision Detection

CSNW

Carrier Sense NetWare

CSU/DSU

Changes the frame types between the LAN and WAN

Data

Information, as recognized by a computer and transmitted across a variety media, from computer or network to another, using a specific protocol, or language.

Data Encryption

Data that is encoded for security reasons, at the sender’s level and then decoded at the recipient’s level.

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Data Link Layer

The Data Link layer is the second lowest layer in the OSI model. It is the last stop before the data packets are placed on the media for transmission. The Data Link layer splits data into frames, which are large areas of data that are split into smaller non-contiguous blocks, for sending on the Physical layer. It also receives acknowledgement frames. It performs error checking and re-transmits frames that were not received correctly.

Default Gateway

When you type the IP address of the gateway routers you have installed on your network, whichever one appears first on the list is considered the default gateway.

Demand Priority

This access method is designed for the 100 Mbps Ethernet standard 100VG-AnyLAN

DHCP

Dynamic Host Configuration Protocol - A method for leasing and maintaining that lease for IP addresses and related information to clients.

Digital Signal

Baseband uses digital signals over a single frequency. (Simple “on” or “off” signal.)

Disaster Recovery

Being able to recover data from a disaster.

Disk Mirroring

The use of two or more hard disks that “mirror” the main one, so that one can take over for the other if it fails.

Disk Striping

Also called data striping, this is the dividing into segments of logically sequential data, such as an individual file, so that the segments can be written to multiple disk drives, in a round-robin fashion. If the processor is capable of reading or writing data faster than a single disk can supply or accept it, the second disk can locate the next segment while data is being transferred from the first disk.

DMA (Direct Memory Access)

A limited form of bus mastering, DMA allows a device to read and write memory without intervention by the CPU.

DNS

Domain Name System

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Appendix E – Glossary

DSMN

DSMN (Directory Service Manager for NetWare) is another add-on utility that is used to integrate user and group account information between the two operating systems.

DUN

Dial-up Networking

EISA Bus

Extended Industry Standard Architecture is a PC bus that converts the PC bus from 16-bits to 32-bits.

Ethernet

A local area network (LAN) recognized as the industry standard.

EtherTalk

A way to run AppleTalk on coaxial cable using an EtherTalk NB NIC.

Event Viewer

A Windows NT utility that will allow you to log any events and errors.

FAT

File Allocation Table

Fax Server

A server on a network that is configured to provide both incoming and outgoing fax services to the entire network.

Fiber-Optic Cable

Optical fibers carry digital signals in the form of modulated pulses of light.

File Server

A network’s central computer, with a very large amount of storage space for shared files.

Firewall

A set of programs running on a network’s gateway server that monitors incoming and outgoing traffic and allows only authorized packets to be transmitted or received.

Frame Relay

An improved version of X.25 packet switching technology.

Frames

A group of bits containing address information, error detection, and other control information, sent over a communications channel.

FTP

File Transfer Protocol

Full-Duplex

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Gateway

A computer that acts as a translator, that enables two networks, using different protocols, to communicate with each other.

GSNW

Gateway Service for NetWare

Half-Duplex

Half-Duplex can send transmissions both ways (send and receive), but only one at a time.

Header

The portion of a packet that contains source and destination addresses, and other information. It precedes the actual data.

HOSTS and LMHOSTS files

Text files that are used to look up and resolve names to IP addresses. HOSTS is used for DNS and LMHOSTS is used for WINS.

HTTP

Hypertext Transfer Protocol

HTTPS

HyperText Transport Protocol Secure

Hub

The center of a cabling system or a network with star topology architecture.

Hybrid Topology

A network topology that combines bus, star, or ring topologies.

ICA

Independent Computing Architecture

ICMP

Internet Control Message Protocol, defined in STD 5, RFC 792, is an extension to the Internet Protocol (IP) that allows for the generation of error messages, test packets, and informational messages related to IP.

ICS

Internet Connection Sharing

IFCONFIG

Shows the user’s network interface configuration

IMAP4

Internet Messaging Access Protocol

Interoperability

The ability of software and hardware to communicate, even though there may be multiple machines from multiple vendors.

IP

Internet Protocol

IP Address

This 32-bit host address defined by the Internet Protocol in STD 5, RFC 791, is usually represented in dotted decimal notation.

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Appendix E – Glossary IPCONFIG

DOS command that tells you the IP address for your computer.

IPsec

A security protocol that works at network layer

IRQ

Interrupt Request causes the processor to temporarily suspend normal instruction execution and to start executing an interrupt handler routine.

ISA Bus

Industry Standard Architecture refers to the bus architecture used in the IBM PC.

ISDN

Integrated Services Digital Network is a set of communication standards that allows a single wire or optical fiber to carry voice, data, and video data sources.

Kerberos

A system for user authentication

L2TP

Layer 2 Tunneling Protocol

LAN

Local Area Network

Laser Transmissions

A wireless network standard that uses laser beams for the transmission of data.

Latency

The time it takes for a packet to go from sender to receiver, across a network connection.

LLC

Logical Link Control – a sublayer of the Data Link Layer

LocalTalk

AppleTalk networks are usually called LocalTalk.

MAC

Media Access Control – a sublayer of the Data Link Layer. The MAC address is the address that is hardwired onto the NIC by the manufacturer, it’s “hardware address.”

Mail Server

Server used for E-mail.

MAN

Metropolitan Area Network

Management Software

The primary software package used by the administrator.

MAU/MSAU

Multistation Access Unit in a Token Ring network, a device to attach multiple network stations in a star topology, internally wired to connect the stations into a logical ring. Specialized Solutions, Inc.

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MCA Bus

Micro Channel Architecture, a 32-bit bus, introduced by IBM for its PS/2 computer line, totally incompatible with the original PC bus.

Media

A method of data transmission.

Media Tester

Tool used for testing the continuity and pin-outs of a cable

Mesh Topology

Every device is connected to every other device by separate cables and has redundant paths.

MHS

Message Handling System – A standard defined by ITU-T as X.400 and by ISO as Message-Oriented Text Interchange Standard (MOTIS). MHS provides the functions for global E-mail transfer among local mail systems, and is used by CompuServe, among others.

Microwave Transmissions

A wireless network standard that uses microwave signals for data transmission.

Multimeter

One of the most basic tools for electronic troubleshooting.

Multistation Access Unit

A type of hub. The actual ring in a Token Ring network is in the hub.

Multitasking

Performing multiple tasks simultaneously.

Narrow-Band Radio

Single Frequency Radio. The transmitter and receiver are tuned to the same frequency. Much like your local radio station.

NAS

Network Attached Storage

NAT

Network Address Translation

NBTSTAT

NetBIOS Statistics

NDS

NetWare Directory Services

NetBIOS

Names used with WINS; protocol as well

Network

A group of computers linked together for the purpose of sharing resources.

Network Adapter Card

Also known as a network interface card. Provides the physical connection to the network cable.

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Appendix E – Glossary Network Administrator

The individual who has complete responsibility for maintaining a network.

Network Interface Card (NIC)

An adapter circuit board installed in a computer that provides a physical connection to a network.

Network Layer

The hardware that is used to construct the network plays an important role at this layer. The network layer handles all the routing information as packets travel from one network to another.

Non-Routable Protocol

A protocol that cannot be routed or passed through routers on a network.

NOS

Network Operating System

NTFS

NT File System

NTSTAT

A TCP/IP utility command that will return information regarding the status of a network.

NWLink

A Windows NT service that allows for interoperability with the NetWare NOS.

Octet

Each part of an IP Address that contains eight bits of data is called an octet.

OSI

Refers to the OSI (Open Systems Interface) Model.

Packets

A generic term used to describe a unit of data. A “packet” may also refer to a frame or datagram, depending on the protocol. A packet actually refers to Application layer data units (APDU).

Passive Hub

Acts as a connection point only.

Password Security

A user has to enter a password to gain access to the network or to shared resources.

Patch Cable

They extend the connection between the computer and the hub or between two hubs.

PCI Bus

A 32-bit architecture bus for PC expansion cards.

PCMCIA Card

PCMCIA (Personal Computer Memory Card International Association) cards are credit card sized expansion buses that are used in portable computers (laptops) to provide the same expandability enjoyed by desktop computers, including network connectivity. Specialized Solutions, Inc.

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Peer-to-Peer

All the computers on the network can act as either a client or server, depending upon the needs of the user.

Performance Monitor

A software tool that is used to monitor the performance of a network server. Although included as part of Windows NT, many third-party applications are available.

Peripheral

A hardware device, such as a printer or scanner.

Physical Layer

The Physical layer is the lowest layer in the OSI Model. This layer determines the interface hardware and the medium that will be used to transmit the data from the Data Link layer.

PING

A way of testing the server to see if it is alive and functioning, and running on TCP/IP.

Plenum

The space between the ceiling and the floor above; used to circulate air through a building.

Port Number

Defines a channel between a device and the processor.

POP3

Post Office Protocol 3

PPP

Point-to-Point Protocol

PPTP

Point-to-Point Tunneling Protocol

Preemptive Multitasking

Introduced in version 3.5 of Windows 3.1, this feature has a different scheme called cooperative multitasking, which means that a process can take control of the CPU and check for other processes. The preemptive feature allows NT to hand out slices of CPU time, and even if a process takes full control, other processes will still run.

Presentation Layer

The Presentation layer formats data exchange, converting character sets and encrypting data, allowing incompatible processes in the Application layer to communicate with the Session layer.

Print Server

Dedicated server for printing.

Protocol Stack

A group of protocols that are used to communicate between computers on a network. The OSI model is the ideal protocol stack.

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Appendix E – Glossary

Proxy Server

One that serves many clients through only one connection; For example, the user is connecting to the Internet via a secondary source, i.e. the proxy server.

Punch Down Tool

Used for “punching” down wire to a block

RAID

Redundant Arrays of Independent Disks

RARP

Uses a MAC address to find an IP address.

RAS

A service provided by Windows NT that allows most of the services provided by a network, including support for dialup and logon, to be accessed via a modem.

Redirector/Requester

Redirects a call from one port to another. For example, redirects a print job from the local port to the network printer.

Reflective Infrared

The signal is beamed towards a central unit, which then routes the signal appropriately.

Repeater

Used to increase cable distances in network environments.

Resources

The services or peripherals that are shared over the network.

Ring Speed

In Token-Ring networks, the ring speed on the NIC is set to either 4 Mbps or 16 Mbps.

Ring Topology

In a Ring topology, the devices are connected in a continuous loop.

RJ-11 Connector

Connector used with standard telephone wire. Flat cable with 2 or 4 conductors.

RJ-45 Connector

Connector used with UTP and STP network cables. Will hold up to 4 pairs of conductors.

Routable Protocol

A protocol that can be routed over the internet or through routers on a network.

Router

A device that forwards packets between networks.

SAN

Storage Area Network

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Satellite Microwave

A wireless network that utilizes microwave signals to transmit data.

Scatter Infrared

Transmission rates are slower with this type, as the signal is designed to bounce off of walls, ceilings, etc. until it reaches the receiver. The effective distance of the signal is limited to about 100 feet.

SDH

Synchronous Digital Hierarchy

Security

The system used to protect data on a network from unauthorized use.

Server

A computer on a network that provides services to other computers.

Server Software

Software that resides on a server.

Session Layer

The Session layer handles such things as security authentication, data transfer, acknowledgments (ACK), connection establishment and release.

Sharing

Allowing files to be shared from one computer to another.

Shielded Twisted Pair

A type of cable in which pairs of conductors are twisted together to prevent possible cross-talk from nearby wiring.

Simplex

A uni-directional data channel, as opposed to duplex.

Single-Frequency Radio

Narrow-Band Radio Transmission

SLIP

Serial Line Internet Protocol, defined in RFC 1055, is software that allows the Internet Protocol (IP), normally used on Ethernet, to be used over a serial link.

SMAU

Smart Multistation Access Unit

SMTP

Simple Mail Transfer Protocol is used to transfer E-mail between computers, usually over Ethernet.

SNMP

Simple Network Management Protocol, the Internet standard protocol defined in STD 15, RFC 1157, was developed to manage nodes on an IP network. SNMP is not limited to TCP/IP.

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Appendix E – Glossary SONET

Synchronous Optical Network

Spread-Spectrum Radio

Spread-spectrum broadcasts over a range of frequencies, so it is less susceptible to eavesdropping. This type of transmission is commonly used to connect multiple LAN segments together.

SSL

Secure Sockets Layer

Star Topology

A LAN topology in which all workstations are wired directly to a central workstation called a hub. If the hub fails, the entire network goes down.

Subnet Mask

Using binary addition, a router can determine what addresses are local and what addresses are for other subnets within the network.

Subnetting

The process of subdividing a network into logical units.

TCP/IP

Transmission Control Protocol over Internet Protocol, the official protocol of the Internet.

TDR

Time-Domain Reflectometer – A cable tester.

Terminator

A connector that has a built-in resistor in order to absorb signals and eliminate signal bounce.

Terrestrial Microwave

A form of microwave communication used for earthbased communication between two buildings, or across large flat open areas, such as bodies of water or deserts.

Thicknet

An Ethernet cable variant commonly known as 10base5, that uses a large diameter, rigid coaxial cable with multiple shielding and an impedance of 50 ohms. Maximum segment length is 500 meters.

Thinnet

A type of coaxial cable whose maximum segment length is 185 meters.

Throughput

The maximum speed that “traffic” can move, measured in Mbps (Megabits per minute).

Token Passing

An access method used in a Token Ring topology.

Token Ring

A LAN topology that uses an access method called token passing.

TokenTalk

A way to run AppleTalk in a Token Ring (IEEE 802.5 Standard) environment. Specialized Solutions, Inc.

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Tone Generator

Connected to the wires at the known location (the room with the outlet), this applies a signal on the wires. The “fox.”

Tone Locator

A receiver set to the frequency of the generator. When the receiver is placed in close proximity to the wire that has the signal applied, it will emit a tone, thus locating the wires. The “hound.”

TRACERT

Trace Route command in NT allows you to specify a remote host and report back on each subsequent router and the times it takes to traverse those routers in a command line interface. Additionally named traceroute in UNIX environments.

Trailer

The part of a data packet that contains the error corrections information.

Transceiver

A device that transmits and receives data.

Transport Layer

The Transport layer is responsible for packaging (and un-packaging) the data for transport, and for the errorfree delivery of the transmitted data.

UDP

User Datagram Protocol, defined in STD 6, RFC 768 is a connectionless protocol, which, like TCP, is layered on top of IP.

UNIX

A major operating system that is primarily used on minicomputers and has many features that are favored in the engineering and scientific environments.

Unshielded Twisted Pair

Twisted network cables that do not have any shielding.

Vampire Tap

Connectors that utilize sharp teeth to pierce the cable jacket to make the connection. Used on transceivers.

VLAN

Virtual LAN

WAN

Wide Area Network

WINIPCFG

A command used to display the current configuration of a Windows computer.

Wire Crimper

Tool for stripping and cutting wire

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Appendix E – Glossary

WINS SERVER

A way for Microsoft hosts to register themselves, resolve and also release the mapping of their network NetBIOS name to an IP address.

Zones

A named Subnetwork used for expanding the LocalTalk network or for relieving traffic on a larger network. AppleTalk can incorporate other types of networks, such as Token Ring, using zones

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Appendix F – Chapter Review Questions and Answers

Appendix F – Chapter Review Questions and Answers The following are the questions found at the end of each chapter along with the correct answers.

Review Questions Chapter 1

1. What is the key difference between a local area network and a wide area network? A LAN is the basic building block (and smallest) of a network. It is confined to a limited area. A WAN is not geographically limited. A WAN is created by connecting LANs together. LANs typically also have much faster communication speed than WANs. 2. What is the main reason for networking computers? To share resources, such as data, applications, and peripheral devices. 3. What is a “sneaker net”? The “old fashioned” way computer users shared resources by taking a file on a floppy disk to the computer that had the services they needed to use. Dragging a printer from computer to computer for users to utilize is another form of a sneaker net. 4. Name some advantages of having centralized documents. Files are easily accessed by all users. Access can be denied to unauthorized users (security), data backups can be more easily and routinely performed. 5. What does MAN stand for and why is it no longer in use? Metropolitan Area Networks have been replaced by the Internet. 6. Name some advantages of a Peer-to-Peer network. Simple to install, configure, and manage (each user manages their own computer) for a small number of workstations (10 or less), inexpensive to install (no need to buy expensive server). 7. Name some disadvantages of a Peer-to-Peer network. No security, loss of performance occurs if expanded over 10 workstations. Workstations need to be close together (in a relatively small area, like one office). Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide 8. Name some advantages of a Server-based network. Centralized location of resources (server). File and resource security available to limit unauthorized access. Ease of data backups. Can be expanded as network grows. Centralized administration. Increased performance on large networks. 9. Name some disadvantages of a Server-based network. Expensive to install (will need to purchase expensive server). More difficult to install and configure, more difficult to manage (needs an administrator). 10. Name the three basic topologies. The three basic topologies are: Bus, Star, and Ring. 11. What is the difference between a physical and logical topology? Physical topologies are the actual wires and hardware that we can see. They represent what the topology looks like. Logical topologies represent the way that a networks functions. 12. Name two media access methods The access methods are CSMA/CD CSMA/CA, Token Passing, and Demand Priority.

Review Questions Chapter 2

1. What is the difference between an operating system and a network operating system? Network operating systems are specialized operating systems designed to function in a network environment. Some NOSs function as the operating system that runs a computer’s stand-alone functions as well as its network interfaces. 2. What is the difference between preemptive and non-preemptive multitasking? Multitasking means that a computer has the ability to perform more than one task at a time. Preemptive multitasking means that the operating system can take control of the processor without a task’s permission. Non-preemptive multitasking is when the task decides when it is done with the CPU.

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Appendix F – Chapter Review Questions and Answers 3. What is the purpose of the redirector? The redirector (in Novell NetWare it is called the requester) forwards requests away from the local bus, redirecting them to the server. The purpose of the redirector is to make network resources look like local resources to the application. 4. NetWare is designed as an operating system that will overlay _____________ environments. NetWare is a reliable operating system that provides excellent performance and security. It is designed as an operating system that will overlay multi-operating system environments. 5. What is NDS? NDS (NetWare Directory Services) is the core of the NetWare operating system. It is a hierarchically organized database that provides security, name service, messaging, routing, web-publishing, management, and file and print services. Organization of network resources such as users, groups, servers, and volumes is also handled with NDS. 6. What are the minimum hardware requirements for installing Novell NetWare version 5? Pentium Class or Higher CPU, 64 MB RAM, 550 MB of free hard drive space. 7. Define interoperability. Interoperability describes the ability of an operating system to interact with other operating systems. 8. Unlike NetWare, Windows NT combines the _____________ and the ___________________ into one. Windows NT combines the operating system and the network operating system into one. 9. What is NTFS? NTFS is the file system in Windows NT and it must be utilized in order to take full advantage of NT’s security features.

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Network + Training & Test Preparation Guide 10. What is a domain? NT uses domains in order to accomplish its security goals. A domain is simply a group of workstations with a shared security database. 11. What are the minimum hardware requirements for Windows NT Server? 476DX-3 CPU, 16 MB RAM, 125 MB free hard drive space. 12. Name some of the services and protocols that Microsoft included with Windows NT to ensure interoperability with NetWare. NWLink is a protocol based on Novell’s IPX/SPX and is used for communication between the two systems. GSNW (Gateway Services for NetWare) provides the gateway between an NT domain and the NetWare server. CSNW (Client Services for NetWare) allows NT workstations to use file and print services on a NetWare server. FPNW (File and Print Services for NetWare) allows NetWare clients to access NT file and print services. DSMN (Directory Service Manager for NetWare) is used to integrate user and group account information between NT and NetWare. Migration Tool for NetWare is used to convert NetWare accounts to NT. 13. What OS is similar to UNIX and is a publicly open system? Linux 14. What type of computer was developed by Apple computer in 1984? The Macintosh 15.What type of network would utilize Windows for Workgroups as an operating system? Windows for Workgroups is a version of Windows 3.1 that includes the ability to run a peer-to-peer network.

Review Questions Chapter 3 1. Who developed the OSI model? The OSI model was developed by ISO (International Organization for Standardization). 2. Name the seven layers of the OSI model. Application, Presentation, Session, Transport, Network, Data Link, and Physical 3. A network adapter card operates at the _______ layer of the OSI model Network layer 306

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Appendix F – Chapter Review Questions and Answers 4. A bridge operates at the ________ layer of the OSI model. Data Link layer 5. A router operates at the _________layer of the OSI model. Network Layer 6. Data compression takes place at the __________ layer of the OSI. Presentation layer 7. Which OSI layer is responsible the MAC address? The Data Link layer 8. What is the function of the Application Layer? The Application layer is responsible for communication between a user’s application and the network. This is not the actual application or program, simply a support layer that allows an application to use the network by acting as a translator. 9. The ____________ layer is responsible for the mechanical and electrical functions of transmitting data over a network. Physical 10. What is the function of the Presentation Layer? The Presentation layer is the translator for the network. It translates data into a format that is compatible with the network and back into a format that is compatible with the computer. 11. Which OSI layer is responsible for establishing, managing, and ending connections? The Session layer 12. What is a MAC address? The MAC address is another name for the 12-digit (6-byte) hexadecimal address that is hardwired on the NIC by the manufacturer. It is a computer’s physical address. 13. Which part of this MAC address is the Device ID? D3-B4-01

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Network + Training & Test Preparation Guide 15. Which OSI layer is responsible for delivering data in sequence, without duplication and error free? The Transport layer 16. The Data Link layer has been split into two sub-layers. What are they? The Logical Link (LLC) layer and the Media Access Control (MAC) layer 17. What is the function of a Gateway? A gateway translates between two networks that use different protocols. A computer with special software serves as a gateway and allows for communication between completely dissimilar networks. 18. Which IEEE standard defines the Logical Link Control (LLC) sub-layer? 802.2 19. What are NDIS and ODI? They are Network Adapter Card interface specifications. They are incompatible with each other. NDIS (Network Driver Interface Specification) was co-developed by Microsoft and 3Com, while ODI (Open Data Link Interface) was co-developed by Novell and Apple. The purpose of these standards is to allow operating system vendors to write multiple drivers for the same NIC. This way more than one protocol can be bound to a single NIC. 20. Describe protocol binding. In order to function, a protocol must be bound to the NIC. This binding process is what links the protocol stacks to the NIC driver. It is possible to bind two protocols the one NIC (such as TCP/IP and IPX/IPX) or to have two NICs with one protocol bound to each one. The order in which these protocols are bound to the NIC determines which one the network operating system will attempt to use first. 21. Which is faster, connection-oriented communication or connectionless communication? Connectionless communication is faster, but connection-oriented communication is more reliable. 22. . Name as many routable protocols as you can remember. AppleTalk, DECnet, IPX/SPX, PPP, PPTP, SLIP, SMB, SNA, TCP/IP, UDP, X.25, XNS 23.. You have expanded your NetBEUI network into two segments and are using an intelligent router to optimize network traffic. Will this work? Why or Why not? 308

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Appendix F – Chapter Review Questions and Answers No, NetBEUI is a non-routable protocol.

Review Questions Chapter 4

1. What is the maximum segment length of Thinnet? 185 meters 2. What is the maximum segment length of Thicknet? 500 meters 3. What type of connectors are used with Coaxial cable? BNC connectors 4. What is the purpose of a transceiver? A transceiver is a device that both transmits and receives data on a network. 5. How is a vampire tap connected? They utilize sharp teeth that puncture the cable to make the connection. 6. What is the purpose of plenum cabling? Plenum grade cabling is used in the plenum (the space between the ceiling and the floor above, which is used to circulate air in a building). Fire codes usually call for special cable in this area because PVC cable gives off poisonous gas and fumes when burned, which would end up being circulated throughout the building. 7. What is the maximum segment length of UTP? 100 meters 8. What is the transmission speed of category 5 cabling? Up to 100 Mbps

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Network + Training & Test Preparation Guide 9. What is the most popular of the cable types? UTP is the less expensive of the twisted pair cable types. It is also flexible and easy to install, making it the most popular cable type. 10. Which twisted pair cabling is less sensitive to EMI? STP is insulated with a foil mesh between the wire pairs, which results in less sensitivity to EMI and crosstalk. 11. What type of connector is used with twisted pair cable? RJ-45 connectors 12. What is the most expensive cable type? Fiber-Optic cable is the ideal cable type for networking. However, it is the most expensive and most difficult to install. 13. What is the least expensive of the cable types? UTP is the least expensive of the cable types. It is also flexible and easy to install, making it the most popular cable type. 14. List some advantages of fiber-optic cable. Fiber-optic supports extremely high bandwidths, segment lengths of up to several miles, and it is not subject to EMI or eavesdropping. 15. What does AWG stand for and what is it? American Wire Gauge (AWG) is the standard that describes wire thickness. The AWG wire number decreases as the wire thickness increases. 16. Describe baseband. Baseband uses the entire capacity of the cable as a single channel. 17. Describe broadband. Broadband allows two or more channels to share the bandwidth of the cable, making the signal flow unidirectional. 18. What is the difference between simplex, half-duplex, and full-duplex communication? Simplex communication is one way, can receive but not send. For example, a pager. Half-duplex communication can send or receive, but not at the same time. For example, a CB radio. Full-duplex can send and receive signals at the same time. For example, the telephone. 310

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Appendix F – Chapter Review Questions and Answers 19. What is the function of a network adapter card? Network Adapter Cards or Network Interface Cards (NICs) are used to connect the computer to the network. (They make the physical connection to the network.) NICs translate the data that computers can understand into signals that can be transmitted over the network medium and back again. 20. In Token Ring networks, what are the two ring speeds available? In a Token Ring network if the correct ring speed is not selected a computer will not be able to connect to the network. The two choices available are 4 Mbps and 16 Mbps. 21. Where would you expect to find a PCMCIA card? PCMCIA (Personal Computer Memory Card International Association) cards are credit card sized expansion buses that are used in portable computers (laptops) to provide the same expandability enjoyed by desktop computers, including network connectivity. 22. What are some of the reasons you would need to install a wireless network? To create a temporary network, to backup a cable-based network, to provide a mobile network environment, for areas where running cable would be impossible or unsightly, outdoor installations and to connect to remote sites such as a ship or oil platform. 23. What are the four basic wireless transmission types? Infrared, Laser, Radio, and Microwave 24. Which is the most secure type of radio wireless network? Spread-Spectrum Radio is more secure than Single-Frequency Radio (Narrow-Band Radio) because it broadcasts over a range of frequencies instead of just one. 25. Which microwave transmission type is used to transmit globally? Satellite microwave is used to transmit globally; Terrestrial microwave is used to transmit over shorter distances.

Review Questions Chapter 5

1. What are the three primary access methods? CSMA/CD & CSMA/CA, Token Passing, and Demand Priority Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide 2. Describe the difference between the two different contention methods CSMA/CD and CSMA/CA. CSMA/CD stands for Carrier Sense Multiple Access with Collision Detection and CSMA/CA stands for Carrier Sense Multiple Access with Collision Avoidance. Both CSMA/CD and CSMA/CA listen to the network cable to determine if it is free (Carrier Sense), if no data is traveling, a CSMA/CD computer will transmit. If there is another computer on the network that transmitted at exactly the same time, a data collision will occur, and both sets of data will be destroyed. CSMA/CD detects that a collision has occurred and waits a specified amount of time before re-transmitting. With CSMA/CA the process is much the same except that instead of just transmitting when it senses that the cable is free, it will send a signal that it is about to transmit. This will cause any other computer that was about to transmit to wait and so data collisions are avoided. This extra step can slow down network traffic, so CSMA/CA is not the most popular of the two contention methods. 3. Why isn’t token passing considered a contention method? A computer on a token passing access method network must possess the token in order to transmit data. Therefore, only one computer at a time will transmit in this kind of architecture, and so, no contention. 4. Describe how data is transmitted in Token Ring architecture A token, which is a special kind of packet, is circulated around the ring from computer to computer in a Token Ring network. A computer that wants to send data onto the network waits until the token is passed to it and takes possession of it. The transmitting computer encodes the token with the data that it wants to transmit, as well as header and trailer information that contain the destination and source addresses, as well as error control information. It then passes the token back out onto the ring where it travels on until it reaches the destination computer. The destination computer copies the data into its buffer and adds some acknowledgment information (or re-transmittal information if it detected errors) and releases the frame back out onto the network where it travels back to the source computer. Assuming that the data was transmitted error-free, the source computer removes the “used” frame from the network and creates a new “free” token to release back out onto the network.

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Appendix F – Chapter Review Questions and Answers 5. What happens if two computers using the demand priority access method transmit at exactly the same time? If the hub receives two transmissions at exactly the same time the one with the highest priority is processed first. If the two transmissions have the same priority level, they are processed at the same time by alternating between the transmissions. 6. How is data transmitted over the network cable? In packets or frames. (Small chunks of data at a time.) 7. What is CRC and what part of the packet is it usually located in? CRC (Cyclical Redundancy Check) is a mathematical calculation that is calculated at the source computer and included in the trailer of the packet. When data arrives at the destination computer, the calculation is redone and if it calculates as it did at the source computer it is assumed that the data arrived intact. 8. What sort of information do packet headers contain? The header contains information such as an alert signal that announces that data is being transmitted, the source and destination addresses and clocking information. 9. What does the “T” in 10BaseT indicate? The first part indicates transmission speed (10 means it transmits at 10 Mbps), the second part “Base” indicates that it uses baseband (single channel) technology and the last part indicates the cabling type, or maximum segment length in the case of coaxial cable. (“T” indicates Twisted-pair). 10. What is the maximum segment length in 10Base2? 185 Meters. The “2” in this case means 2 times 100 meters, but in the case of Thinnet coaxial cable the maximum segment length is 185 meters. 11. What type of connectors are used in 10Base5? BNC connectors 12. What type of cable is used in 10BaseFL? Fiber-Optic 13. Name the two main 100 Mbps Ethernet Standards. 100VG-AnyLAN, also called 100BaseVG, VG, and AnyLAN. The VG stands for Voice Grade. 100BaseX is sometimes called Fast Ethernet. It has different specifications depending upon the type of cabling used (hence the “X” in the area that indicates cable type). Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide 14. Which IEEE Specification defines Ethernet? The IEEE 802.3 standard 15. Which IEEE Specification defines Token Ring? The IEEE 802.5 standard 16. What are the two transmission speeds of Token Ring? 4 Mbps and 16 Mbps 17. How are data collisions avoided in the Token Ring architecture? A computer must posses the token in order to transmit data. Since no other computer can transmit while one computer has the token, data collisions are avoided. 18. Describe beaconing as it applies to Token Ring architecture. The active monitor (which is the first computer to go online) is responsible for monitoring network activity to make sure that frames are being sent and received accurately. It also ensures that only one token is traveling the ring at a time and investigates any frames that have traveled around the ring more than once. It does this by transmitting a signal every seven seconds. This signal is called beaconing and it travels from computer to computer. If a computer doesn’t receive an expected signal from its upstream neighbor it will notify the monitor that a problem may exist. 19. Which way does data travel in a Token Ring network? Which way data travels in a Token Ring network is a matter of convention. IEEE 802.5 says it travels clockwise, while IBM says that it travels counter-clockwise. It can be either depending upon how it is set up. The main thing is that data only travels in one direction on a Token Ring network. It is more commonly set up to travel clockwise, however. 20. What is a SMAU? SMAU stands for Smart Multistation Access Unit. This is a hub that has all of the features of an active hub (regenerates or amplifies the signal) with additional capabilities such as certain network management functions. A SMAU may have the capability to shut down a connection that is producing errors thereby allowing the rest of the network to function. 21. Describe a MIC connector. MIC (Media Interface Connectors) are connectors that have neither male nor female ends. Any connector can be connected to another MIC connector. They are also called hermaphrodite connectors.

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Appendix F – Chapter Review Questions and Answers 22. How does a computer on a LocalTalk network obtain its address? When a computer first comes online in a LocalTalk network it randomly selects an address from a range of allowable addresses. It then broadcasts the address to determine if any other computer on the network is using it. If no other computer is using the address, it stores it to use each time it connects to the network. 23. What is the purpose of AppleShare? AppleShare is the name of the file server on an AppleTalk network. It also provides a print server. 24. What type of access method is utilized by an ARCNet network? Token-passing. 25. How does data flow in an ARCNet network? The token is passed around the network in numerical order. It first goes to computer #1 and then #2, etc. It does this even if computer #1 is at the opposite end of the network from computer #2.

Review Questions Chapter 6

1. What are the two tools required to initiate a network design? All you need to start a network project is a pencil and some paper. 2. What are the two areas of concern when starting a network project? You will need to consider the customer and the network goals. 3. What are the two most prominent reasons to choose a peer-to-peer network? The best reasons for using peer-to-peer are its simplicity and low cost. 4. What is the number one reason for choosing a client/server network? The number one reason for using a client/server network is security. 5. Is NetBEUI a good protocol to use with a large WAN? No, NetBEUI is a non-routable protocol and will not interface with routers.

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Network + Training & Test Preparation Guide 6. Your client is installing a small Ethernet network and trying to save money at the same time. However, he intends to expand the network in the future. Give one reason why you should recommend that he spend a little more now and install CAT 6 cabling instead of CAT 5. It will be less costly to install CAT 6 now than to replace the CAT 5 later when the network needs to be upgraded from 100 Mbps to 1 Gbps to handle the higher traffic. 7. You are expanding your network and will need to invest in 50 to 100 new network cards. Your accounting office found a really good deal on network cards, but they are not all the same. Why should you refuse this offer? First, you cannot be sure that they will meet the specifications of your network. Also, having to maintain a variety of network cards will increase the workload of your IS department – it is better to standardize network cards in a large network. 8. Your company just bought ten new computers and all are guaranteed to meet the minimum requirements of Windows XP. Was this a good purchase? No – the minimum requirements are just enough to run the NOS, but not enough to run it efficiently. 9. How do you know if a new piece of hardware will work with Windows XP? Check the Windows Catalog on the web at www.microsoft.com/windows/catalog.

Review Questions Chapter 7

1. What is the difference between a hub and a MAU? Hubs are used with Ethernet networks and MAUs are used with Token Ring networks. 2. What is the difference between an active hub and a passive hub? Active hubs are used to connect nodes and boost the signal strengths. An active hub requires some input power. Passive hubs are used only to make connections.

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Appendix F – Chapter Review Questions and Answers 3. Define a repeater, a bridge, a router, and a gateway. Repeater - A repeater is a device that is used to extend the cable lengths of a network segment. They do not translate or filter any information. They do however, amplify the signal thereby compensating for signal loss due to long cables. Repeaters work in the Physical layer of the OSI model. Bridge - A bridge does the same things as a repeater but has one additional feature. A bridge can be used to isolate segments on a LAN, thus reducing the traffic for each segment. Bridges work in the Data Link layer of the OSI model. Router - A router has all the features of a bridge, but it can switch packets across multiple networks. They can also determine the best path for “routing” traffic and filter broadcast traffic to the local segment. Not all network protocols will work with a router. For example, NetBEUI is not routable. Gateway - Gateways make it possible to connect different network architectures. Think of a gateway as a computer that acts as a translator between two networks that don’t speak the same language. 4. What is analog communication? Analog communication is based on PSTN or public switched telephone network. 5. A form of digital line that is capable of 1.544 Mbps transmissions is called? T1 6. Name three advanced WAN environments. Frame Relay, ISDN, and SONET 7. What are the two components of remote network accessing? RAS (remote access server) and DUN (dial up networking). 8. Name three RAS protocols. SLIP, PPP, PPTP and L2TP 9. Name four forms of RAS security. Auditing, Callback Security, Security host, and PPTP filtering. 10. Describe the difference between BAUD and bps. BAUD rate is the number in cycles per second of the carrier signal of a modem. BAUD is limited to 2400 bps. A bps or bit per second is the actual data transmission rate of a modem. In older modems, BAUD and bps were the same thing. Specialized Solutions, Inc.

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Review Questions Chapter 8

1. What are the four layers that make up the TCP/IP protocol suite? The four layers of TCP/IP are: Application, Transport, Internet and Network Interface. 2. How many primary protocols are used to make the TCP/IP Suite? There are five primary protocols: they are – TCP, UDP, IP, ICMP, and ARP. 3. Name three of the five other protocols used within TCP/IP Additional protocols are: POP3, SMTP, FTP, SNMP, and HTTP. 4. What is the purpose of DNS? The Domain Name System is used to resolve host names into IP addresses. 5. What is an FQDN and give an example? FQDN is a Fully Qualified Domain Name. An example is http://www.microsoft.com. HTU

6. What is a domain? A domain is a group of computers that share a common general purpose. 7. Who is responsible for maintaining top-level domains? The InterNIC (Internet Network Information Center) is responsible for top-level domain names. 8. Which of the name resolution services will work only in Windows? WINS 9. IPv4 addresses consist of a ______ bit number. 32 10. What is the value of the leading bit (one on the far left) for a Class A IP address? Class B? Class C?

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Class A

01-126

(leading bit is 0)

Class B

128-191

(leading bit is 1)

Class C

192-223

(leading bits 11)

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Appendix F – Chapter Review Questions and Answers 11. Subnetting is the process of breaking an IP address into _________ and ________ groups Subnetting is the process of breaking an IP address into meaningful and manageable groups. U

U

U

U

12. What are five reasons to use subnetting? Connect physically remote local networks Connect a mix of network technologies (Ethernet and Token Ring) Allow an unlimited number of hosts to communicate Reduce network traffic by limiting broadcast and local traffic to a single segment

Review Questions Chapter 9

1. You are the manager of a large network and have been getting complaints about the system being slow. What kind of software package can you purchase to help analyze your network? Network Management Software is used to analyze network traffic and network status. 2. In order for your new network management software to monitor the activities of the entire network, each device will need to be _________ compliant. SNMP (Simple Network Management Protocol) 3. TCP/IP provides several tools that you can use to validate the statistics of your network. List as many as you can. Event Viewer, ROUTE, NBTSTAT, NETSTAT and TRACERT.

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Review Questions Chapter 10

1. What are the two requirements of user level logon? The user must type in a Username and a Password. 2. In a share level model, passwords are assigned to __________. Resources 3. What is the function of a firewall? A firewall is used to prevent unauthorized access to your network from outside via the Internet. It can also be configured to prevent unauthorized transmissions from leaving your network. 4. The acronym RAID stands for____________? Redundant Array of Independent Disks or Redundant Array of Inexpensive Disks. 5. What are the three most common levels of RAID? RAID 0 Non-redundant striped array RAID 1 Mirrored arrays RAID 5 Striped array with parity 6. What purpose does encryption play in your security model? Encryption encodes a message so that it cannot be read if it is intercepted during transmission.

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Appendix F – Chapter Review Questions and Answers

Review Questions Chapter 11

1. What are the three primary steps to take when troubleshooting? The three steps to troubleshooting are: Define the Problem, Isolate the Problem, and Repair the Problem. 2. After repairing a problem, are you finished with the troubleshooting process? NO – You still need to confirm the repair and document the problem and solution. 3. You are troubleshooting a cable problem. You have found the cabinet with the patch panel and hub, but need to know which of the 50 cables goes to the accounting office. What would be the best tool to help you locate the cable in question? The best tool for isolating a single cable from many is the tone generator or tone locator. The fox and hound. 4. You have located the cable in question #3, and think it might be shorted. What tool would you need to find the short? TDRs (Time-Domain Reflectometers) are used to locate shorts in cables. 5. You are working with a TCP/IP network and want to confirm the protocol stack in a specific workstation. What utility can you use to confirm the protocol stack is good? PING the loopback IP. 6. What is the loopback IP address? 127.0.0.1 7. You need to know the IP address of a workstation. What TCP/IP utility can you use to find the IP address of the workstation? You can use IPCONFIG from a DOS prompt or if using Windows, WINIPCFG from the RUN command. 8. You have just connected a workstation to the network. What is the easiest way to tell if the network card can “see” the network? If the network card has indicator lights, you should see the green light that indicates that the network card has detected the presence of a network.

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Network + Training & Test Preparation Guide 9. What is the difference between bandwidth and throughput? Bandwidth is the amount of traffic that a network can handle at a given time. Throughput is the maximum speed that a message can be transmitted. 10. You have a Windows 2000 network and received complaints that the server is running slow. What utility can you use to determine the performance of the server? Performance Monitor

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Appendix F – Chapter Review Questions and Answers

Index 1 100BaseX, 136 100VG-AnyLAN, 136 10Base2, 135 10Base5, 135 10BaseFL, 135 10BaseT, 135 A access method, 128 Active Directory, 59 active hubs, 41 Address Resolution Protocol, 87 Analog, 109 AppleShare, 142 AppleTalk, 142 Application Layer, 68 application server, 31 ARCNet, 143 ARP, 87 ATM, 186 attenuation,78 attributes, 54 AUI connector, 87 AWG, 106 B backbone, 33 backup utility, 246 Bandwidth, 106 Banyan VINES, 60 base 106 Beaconing, 139 binding, 83 BNC, 97 Boot Prom’s, 300 Boot Sector, 251 BOOTP, 211 BRI, 186 bridge, 78 Broadband, 106

Broadband Optical Telepoint, 117 brouter, 79 C Carrier Sense Multiple Access with Collision Detection (CSMA/CD, 38,128 Carriers, 180 Category 3, 80 Category 5,136 Cellular Networking, 118 Change, 57 Circuit-switched, 184 Class A, 215 Class B, 215 Class C, 215 client software, 52 Client Software, 52 clients, 31 Clocking, 109 cloud, 88 coaxial cable, 97 Computer compatibility, 171 connection-oriented, 83 continuity, 263 CSMA/CD, 38,80 CSNW, 59 CSU/DSU, 181 Cyclical Redundancy Check (CRC), 139 D Data Link Layer, 58 Data Protection, 40 DECnet, 85 demand priority, 129 DES (Data Encryption Standard), 250 Differential backup, 246 Digital, 97 Direct Memory Access (DMA), 99 DLC, 88 DMA, 110 domain, 58 domain controller, 58 Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Domain Name Service (DNS), 209 Domain Reflectometer (TDR), 265 DSMN, 59 Dynamic Host Control Protocol (DHCP), 211

HOSTS file, 211 HTTP, 207 HTTPS, 207 hubs, 40 hybrid topologies, 35 I

E EES, 251 EISA, 113 EMI, 164 environment, 29 Ethernet, 38 EtherTalk, 142 Event Viewer, 235 F Fast Ethernet, 39 FAT, 57,303 fault tolerance., 246 FDDI - Fiber Distributed Data, 186 fiber-optic, 103 File Infectors, 251 fire codes, 106 firewall, 244 FPNW, 59 Frame Relay, 184,303 FTP, 74 Full backup, 246 Full Control, 57 Full-Duplex, 106

I/O port number, 111 IBM cabling, 103 IBM Type 3 UTP, 140 ICA, 193 ICMP, 90,206 ICS, 212 IFCONFIG, 287,304 IMAP4, 206 Incremental backup, 226 Infrared, 116 Institute for Electrical and Electronic Engineers, Inc. (IEEE), 80 Internet Control Message Protocol, 206 Internet Protocol (IP), 86 interoperability, 58 IP, 205 IP address, 214 IPCONFIG, 237 IPsec, 192 IPv6, 217 IPX, 85 IRQ, 111 ISA, 113,305 ISDN, 186

G gateway, 79 gateways, 79 Gateways, 179 Gigabit Ethernet, 136 ground probe, 263 Group policies, 59 GSNW, 59 H Half-Duplex, 106,304 headers, 132 Headers, 132 324

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K Kerberos, 193 L L2TP, 193 LAN, 30 Laser, 116,245 LAT, 88 Layer Two Tunneling Protocol, 193 Linux, 60 LLC, 71 LMHOSTS, 211 LocalTalk, 142

Appendix F – Chapter Review Questions and Answers logical topology, 35 LSL, 85 M Macintosh, 61 Macro Virus, 252 Managing User Accounts, 52 MAU, 140,305 MAUs - Multiple Access Units, 140,305 media access methods, 38 Media Compatibility, 171 Media Tester, 263 mesh topology, 35 MHS, 55 MIB (Management Information Base), 233 MIC (Media Interface Connectors), 140 Microwave, 118 MLID, 85 modem, 188 MSAU, 40,305 Multimeter, 263 multitasking, 48,306 N NAT, 212 NBTSTAT, 288 NCP, 85 NDIS, 82 NDS (NetWare Directory Services), 54 NetBEUI, 89 NETBIOS, 89 , 235 NetWare, 54 NetWare Client32 for DOS, 56 NetWare Client32 for Macintosh, 56 NetWare Client32 for OS/2, 56 NetWare file server, 54 NetWare Print Services, 55 NetWare security, 54 Network Adapter Cards, 109 Network Layer, 70 Network Neighborhood, 49 Network standards, 134 Network Time Protocol (NTP), 87 Network-attached storage (NAS), 248

NFS, 87 No Access, 45 NOS – Network Operating System, 47 , 237 NTFS, 49,307 Null-Modem, 190 NWLink, 86 O ODI, 82 Open Systems Interface or Interconnection (OSI), 67 operating system, 47 OS/2, 51 P Packet switching, 88 Packet-Radio Networking, 118 packets, 75 parallel communication, 109 passive hub, 40 Passwords, 241 Patch Panel, 102 PCI, 113 PCMCIA, 113 peer-to-peer, 32 Peer-to-peer LANs, 49 PGP, 251 physical topologies, 35 Ping, 237 PING, 237 plenum, 106 PPP, 90,192 PPTP, 90,192 Preemptive multitasking, 48,308 PRI, 187 protocol, 38 protocols, 38 proxy server, 212 Punch Down Tool, 250 R Radio, 117 RAID, 245 RARP, 237 Specialized Solutions, Inc.

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Network + Training & Test Preparation Guide Read, 57 redirector, 53 Reflective Infrared, 117 relative humidity, 164 Remote Access Server or RAS, 190 removable disks, 245 removable optical disk, 245 repeater, 178 requester, 53 ring topology, 34 RIP, 87 ROUTE, 235 router, 78 routers, 78 RPC, 90 RSA, 250 S SAP, 86 Satellite Station Networking, 118 Scatter Infrared, 310 SDH, 187 security, 310 Security, 310 segment, 33 serial communication, 109 Server room, 164 Server Software, 52 server-based network, 31 Server-based network, 31 servers, 31 sharing applications, 29 signal bounce, 33 Simple Network Management Protocol (SNMP), 207 Simplex, 106 SLIP, 90,191 SMAU, 140,310 SMB, 86 SMDS, 187 SMTP, 87,207 SNA, 86 sneaker net, 29 SNMP, 90,207 Software analyzers, 265 SONET, 187 SPX, 85 326

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SSL, 193 Standards, 80 star topology, 34 Storage Area Network (SAN), 248 STP, 101 Subnetting, 219 T tape backup, 245 TCP, 86,204 Telnet, 87 terminator, 311 thicknet, 97 Thinnet, 97 throughput, 273 TLS, 193 token passing, 38 token ring, 35 topology, 33 , 235 Trailer, 132 transceiver, 99 Transport Layer, 69 Trivial File Transfer Protocol (TFTP), 87 Trojan Horses, 252 troubleshooting, 257 trunk, 33 twisted-pair, 100 U UDP, 86,205 UNIX, 59 User Datagram Protocol (UDP), 86 UTP, 101 V vampire taps, 100 virtual connections, 76 Viruses, 251 VLAN, 185 VPN’s (Virtual Private Networks), 250

Appendix F – Chapter Review Questions and Answers W WAN, 30 Windows 2000, 50 Windows 95/98, 49 Windows for Workgroups, 137 WINS, 210 Wire Crimper, 262 Wireless, 19, 36 U

U

wireless network, 36 Wireless NICs, 112 workstation, 31 X X.25, 88 XDR, 90 XNS, 88

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