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Introduction to IP Multicast Session 303
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© 1999, Cisco Systems, Inc.
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Other Related Presentations • Multicast Sessions Session #
Title
303
Introduction to IP Multicast
306
PIM Protocol Concepts
314
Deploying IP Multicast
320
Advances in IP Multicast
• MBGP Related Sessions Session #
303 1011_05F9_c3
Title
309
Deploying BGP
317
Advanced BGP and Troubleshooting 3
© 1999, Cisco Systems, Inc.
Agenda
• What Problem Does IP Multicast Solve? • The IP Multicast Service Model • Host to Router Multicast Protocols • Multicast Routing Protocols
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Two Inefficient Multipoint Techniques Multiple Unicasts
Broadcast
Chicago
Chicago
New York
San Francisco
San Francisco
New York
Paris
Paris
Tokyo Tokyo
Three Copies of the Same Packet Are Transmitted
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The Entire Network Receives the Packet Even if the Receivers Are Only a Few
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© 1999, Cisco Systems, Inc.
Multicast Is the Answer Multicast Group
• Multicast transmission: sends single multicast packet addressed to all intended recipients Introduces a new class of IP Addresses, Class D 224.0.0.0 239.255.255.255 Efficient communication and transmission Performance optimizations Enables truly distributed applications Requires intelligent networking devices (to dynamically build efficient paths to all destinations). Supports all underlying network types. 303 1011_05F9_c3
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Apps that Benefit from IP Multicast • Multimedia Streaming media Training, corporate communications Conferencing—video/audio
• Data warehousing, finance applications • Any one-to-many data push applications 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
IP Multicasting Fundamentals of IP Multicasting 303 1011_05F9_c3
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IP Multicast Group Concept Group Member 3
1. If you send to group address, all members receive it 2. You must be a “member” of a group to receive it data 3. You do not have to be a member of a group to send to a group
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B
D “Non” Group Member
C
E
Group Member 2
Group Member 1
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© 1999, Cisco Systems, Inc.
IP Multicast Concept Broken into Two Components 1. IP multicast “routing” 2. End station group management (joins and leaves)
Source
Router Infrastructure • IP multicast routing • Floods, grafts, prunes • PIM—Protocol Independent Multicast • MBGP/MSDP—Multiprotocol Border Gateway Protocol/Multicast Source Discovery Protocol
A
B
C
D
E
End Stations • IGMP (Internet Group Management Protocol) • Group joins/leaves and group maintenance 303 1011_05F9_c3
Receiver
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IP Multicast Service Model • IP group addresses Class D address—high-order 4 bits are set (1110)=(224.0.0.0) Range from 224.0.0.0 through 239.255.255.255
• Well known addresses designated by IANA Reserved use: 224.0.0.0 through 224.0.0.255 224.0.0.1—all systems on subnet 224.0.0.2—all routers on subnet See “http://www.isi.edu/in-notes/iana/assignments/multicast-addresses”
• Transient addresses, assigned and reclaimed dynamically Global scope: 224.0.1.0-238.255.255.255 Limited Scope: 239.0.0.0-239.255.255.255 Site-local scope: 239.255.0.0/16 Organization-local scope: 239.192.0.0/16 303 1011_05F9_c3
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IP Multicasting Host to Router Protocols
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Module Agenda
• MAC Layer multicast addresses • IGMPv1 • IGMPv2 • How do we constrain Multicast Flooding on Layer-2 switches? 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Review— Layer 3 Multicast Addressing • IP group addresses 224.0.0.0–239.255.255.255 • “Class D” addresses = high order bits of “1110” • Special reserved group addresses: 224.0.0.0–224.0.0.255: 224.0.0.1
All systems on this subnet
224.0.0.2
All routers on this subnet
224.0.0.13 All PIM routers 303 1011_05F9_c3
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Layer 2 Multicast Addressing— (Ethernet and FDDI) A Layer 3 IPmc Address Maps to a Layer 2 Multicast Address: 32 Bits 23 Bits
239.255.0.1 01-00-5e-7f-00-01 24 Bits
24 Bits 48 Bits
Be Aware of the Overlap of Layer 3 Addresses to Layer 2 Addresses 32:1 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Layer 2 Multicast Addressing— (Token Ring) A Layer 3 IPmc Address Maps to a Single Token Ring Functional Address or the All Ones’ Broadcast Address:
224.x.x.x
224.x.x.x
c0-00-00-04-00-00
ff-ff-ff-ff-ff-ff
(Shown in Token Ring, Non-Canonical Format)
Cisco Router Allows You to Determine Which Method You Want Results in High Levels of Unwanted Interrupts for Non-Interested Hosts— Broadcast Behavior 303 1011_05F9_c3
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IGMP Internet Group Management Protocol • How hosts tell routers about group membership • Routers solicit group membership from directly connected hosts • RFC 1112 specifies first version of IGMP • RFC 2236 specifies current version of IGMP • Supported on UNIX systems, PCs, and MACs 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
IGMPv1
• RFC 1112—“host extensions for IP multicasting” Membership queries Querier sends IGMP query messages to 224.0.0.1 with ttl = 1 One router on LAN is designated/elected to send queries Query interval 60 Default (Cisco tuneable upwards) Membership reports IGMP report sent by one host suppresses sending by others Restrict to one report per group per LAN Unsolicited reports sent by host, when it first joins the group 303 1011_05F9_c3
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IGMPv1—Joining a Group H1
H2
224.1.1.1
H3
Report
IGMPv1
• Joining member sends report to 224.1.1.1 immediately upon joining 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
IGMPv1—General Queries H1
H2
H3
General Query to 224.0.0.1 IGMPv1 Multicast Router
• Periodically sends general queries to 224.0.0.1 to determine memberships 303 1011_05F9_c3
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IGMPv1—Maintaining a Group 224.1.1.1
H1
X
Suppressed
224.1.1.1
H2
H3
X
Report
#3
224.1.1.1 Suppressed
#3
#2
Query to 224.0.0.1
#1
IGMPv1 #1 #2 #3 303 1011_05F9_c3
Router sends periodic queries One member per group per subnet reports Other members suppress reports 21
© 1999, Cisco Systems, Inc.
IGMPv1—Leaving a Group H1
H2
H3
Query to 224.0.0.1 IGMPv1 • Router sends periodic queries • Hosts silently leave group • Router continues sending periodic queries • No Reports for group received by router • Group times out 303 1011_05F9_c3
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IGMPv2 • RFC 2236 Group-specific query Router checks to make sure last interested receiver has left before ceasing multicast forwarding for a specific group Leave group message Host sends leave message if it leaves the group and is the last member (reduces leave latency in comparison to v1) 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
IGMPv2—(Cont.)
• Querier election mechanism On multi-access networks, an IGMP querier router is elected based on lowest IP address. Only the querier router sends queries
• Query-interval response time General queries specify “maximum response time” which inform hosts of the maximum time within which a host must respond to general query. (Improves burstiness of the responses)
• Backward compatible with IGMPv1 303 1011_05F9_c3
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IGMPv2—Joining a Group 1.1.1.10 H1 H1
224.1.1.1
1.1.1.11
1.1.1.12
H2
H3 H3
Report 1.1.1.1 rtr-a
• Joining member sends report to 224.1.1.1 immediately upon joining (same as IGMPv1) 303 1011_05F9_c3
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IGMPv2—Joining a Group 1.1.1.10
1.1.1.11
1.1.1.12
H1 H1
H2
H3 H3
1.1.1.1 IGMP State in “rtr-a”
rtr-a
rtr-a>show ip igmp group (command to see what groups joined) IGMP Connected Group Membership Group Address Interface Uptime Expires Last Reporter 224.1.1.1 Ethernet0 6d17h 00:02:31 1.1.1.11
Only Displays Last Reporter, Just Needs to Maintain Group State 303 1011_05F9_c3
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IGMPv2—Querier Election 1.1.1.10
1.1.1.11
1.1.1.12
H1
H2
H3
Query
1.1.1.2
IGMP Non-Querier
1.1.1.1
IGMP Querier
IGMPv2 rtr-b
Query
rtr-a
• Initially all routers send out a Query • Router with lowest IP address “elected” querier • Other routers become “Non-Queries” 303 1011_05F9_c3
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IGMPv2—Querier Election Determining which Router Is the IGMP Querier rtr-a>show ip igmp interface e0 Ethernet0 is up, line protocol is up Internet address is 1.1.1.1, subnet mask is 255.255.255.0 IGMP is enabled on interface Current IGMP version is 2 CGMP is disabled on interface IGMP query interval is 60 seconds IGMP querier timeout is 120 seconds IGMP max query response time is 10 seconds Inbound IGMP access group is not set Multicast routing is enabled on interface Multicast TTL threshold is 0 Multicast designated router (DR) is 1.1.1.1 (this system) IGMP querying router is 1.1.1.1 (this system) Multicast groups joined: 224.0.1.40 224.2.127.254
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IGMPv2—Maintaining a Group 1.1.1.10 224.1.1.1
1.1.1.11 224.1.1.1
H1
1.1.1.12 224.1.1.1
H2
X
H3
X Report
Suppressed
Suppressed 1.1.1.1
Query
IGMPv2
• Router sends periodic queries • One member per group per subnet reports • Other members suppress reports 303 1011_05F9_c3
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IGMPv2—Leaving a Group 1.1.1.10
1.1.1.11
1.1.1.12
H1
H2
H3
1.1.1.1 rtr-a
IGMP State in “rtr-a” before Leave rtr-a>sh ip igmp group IGMP Connected Group Membership Group Address Interface Uptime 224.1.1.1 Ethernet0 6d17h
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Last Reporter 1.1.1.11
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IGMPv2—Leaving a Group 1.1.1.10
1.1.1.11 224.1.1.1
H1
1.1.1.12 224.1.1.1
H2
Report to #3 224.1.1.1
Leave to #1 224.0.0.2
1.1.1.1 rtr-a
• • • • 303 1011_05F9_c3
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Group Specific Query to 224.1.1.1 #2
H2 leaves group; sends Leave message Router sends Group specific query A remaining member host sends report Group remains active 31
© 1999, Cisco Systems, Inc.
IGMPv2—Leaving a Group 1.1.1.10
1.1.1.11
1.1.1.12
H1
H2
H3
1.1.1.1 rtr-a
IGMP State in “rtr-a” after H2 Leaves rtr-a>sh ip igmp group IGMP Connected Group Membership Group Address Interface Uptime 224.1.1.1 Ethernet0 6d17h
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Last Reporter 1.1.1.12
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IGMPv2—Leaving a Group 1.1.1.10
1.1.1.11
H1
1.1.1.12 224.1.1.1
H2
H3
Leave to #1 224.0.0.2 1.1.1.1 rtr-a
• • • •
Group Specific Query to 224.1.1.1 #2
Last host leaves group; sends Leave message Router sends Group specific query No report is received Group times out
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© 1999, Cisco Systems, Inc.
IGMPv2—Leaving a Group 1.1.1.10
1.1.1.11
1.1.1.12
H1
H2
H3
1.1.1.1 rtr-a
IGMP State in “rtr-a” after H3 Leaves rtr-a>sh ip igmp group IGMP Connected Group Membership Group Address Interface Uptime
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Building a Campus Network for IP Multicast (IPmc)
“
IPmc is the most common emerging factor that customers FORGET to plan/design for when “flattening” their networks with switching.
”
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Without Multicast Control Interested MCG1 Listener
VLAN 1 MC Group 1
Uninterested MCG1 Listener
ISL Trunk
MC Group 2 VLAN 2
Interested MCG2 Listener Uninterested MCG2 Listener
• Uninterested listeners receive the multicast 303 1011_05F9_c3
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With Multicast Control Interested MCG1 Listener
VLAN 1 MC Group 1
Uninterested MCG1 Listener
ISL Trunk
MC Group 2 VLAN 2
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Interested MCG2 Listener Uninterested MCG2 Listener
• Only interested listeners receive the multicast 37
© 1999, Cisco Systems, Inc.
Constraining Multicast Flooding at Layer 2 • 802.1 GMRP GARP Multicast Registration Protocol
• IGMP Snooping Internet Group Membership Protocol Snooping on Layer 2 switches
• CGMP Cisco Group Membership Protocol 303 1011_05F9_c3
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GMRP Overview
• New standard from IEEE 802.1 Committee • Required changes to the IEEE 802.3 Ethernet Frame Length 1518 Bytes extended to 1522 Bytes
• Both Host and Layer 2 switch will need upgrades to support • IGMP is still required on the Host 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Cisco Group Management Protocol (CGMP) • Uses Standard MAC-Layer Multicast Addresses to constrain flooding • No changes to end systems—CGMP is transparent • Dynamically programs switches based on IGMP Reports and Leaves. • Resource preservation: Network bandwidth Router leave processing with CGMP leave processing Host CPU 303 1011_05F9_c3
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CGMP Overview • High-performance Layer 2 IPmc switching maintained • CGMP dynamically programs the switch table with multicast address information
PIM
IGMP Report
CGMP
• Requires no host changes
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IGMP Snooping • Give the Switch a Layer-3 capability • Peer into every packet to determine if it is an IGMP report or leave message • Will also dynamically learn about various multicast routers and multicast sources • Done in hardware on Cat5K, 6K, and Snooping operations performed in hardware—performance
• Will interoperate with other switches using CGMP 303 1011_05F9_c3
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Host to Router Protocols Summary • GMRP: GARP Multicast Registration Protocol • IGMP: Internet Group Membership Protocol • CGMP: Cisco Group Membership Protocol • IGMP Snooping: should be done in hardware • Shared Hubs and switches that don’t constrain multicast flooding will need to be replaced 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
IP Multicasting Routing Protocols
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IP Multicast Concept Broken into Two Components 1. IP multicast “routing” 2. End station group management (joins and leaves)
Source
Router Infrastructure • IP multicast routing • Floods, grafts, prunes A • PIM—Protocol Independent Multicast • MBGP/MSDP—Multiprotocol Border Gateway Protocol/Multicast Source Discovery Protocol
B
D
C
E
End Stations • IGMP (Internet Group Management Protocol) • Group joins/leaves and group maintenance 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Multicast Routing Basics • The Destination IP Address in a Multicast Datagram is the Multicast Group Address We can’t route from the source to a virtual destination
• Multicast routing is backwards from unicast routing Unicast routing is concerned about where the packet is going—Destination-based Multicast routing is concerned about where the packet came from—Source-based 303 1011_05F9_c3
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Multicast Routing Basics • Source-Based Routing Since we have to route from the receiver to the source, there must be a mechanism for informing all routers in the network about active sources on each group Since distribution trees are built from a receiver perspective, prior source knowledge is implied unless another mechanism exists to build the tree 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Multicasting Protocol Basics • Multicast routing protocol responsibilities Build and maintain distribution trees Provide mechanism for informing all routers about active sources and groups
• How do we inform routers about active sources and groups? Flood to all routers —Dense Rendezvous Mechanism—Sparse 303 1011_05F9_c3
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Types of Multicast Protocols • Dense-mode Flood and prune behavior Create state in every router for every source, at all times Support for source or shortest-path-trees only
• Sparse-mode Explicit join behavior Support for source and shared-trees Typically use some sort of bootstrap method to act as a clearing-house of information about active sources and groups (e.g. Rendezvous Point or Core Router) 303 1011_05F9_c3
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© 1999, Cisco Systems, Inc.
Multicast Routing Basics • Multicast distribution trees Source-trees (S,G) Shared-trees (*,G)
• Multicast routing uses— “Reverse path forwarding” to build distribution trees and ensure packets are arriving on the correct interface
• A Unicast routing protocol— Is used to determine this “reverse-path” which is the best unicast path from the receiver to the source 303 1011_05F9_c3
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Multicast Forwarding Reverse Path Forwarding (RPF) • How is RPF used to build Distribution Trees? Multicast distribution trees are built hop-by-hop, by determining the best next-hop to the unicast source speaking on a particular group. After the next-hop is determined, Joins or Grafts are sent out what is called the RPF interface, or the interface with the shortest administrative distance to the source. This builds the tree from the receiver towards the source
• What is the RPF check? The routing table used for multicasting is checked against the “source” address in the multicast datagram If the datagram arrived on the interface specified in the routing table for the source address; then the RPF check succeeds Otherwise, the RPF check fails
Packet is never forwarded back out the RPF interface! 303 1011_05F9_c3
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Multicast Forwarding Example: RPF Checking—PIM Dense-Mode
Source 151.10.3.21
Router will Forward Until Pruned Multicast Dist. Tree Multicast Packets RPF Failures
RPF Check Fails Packet Arrived on Wrong Interface!
Note: Assumes an active Receiver is on each LAN Segment 303 1011_05F9_c3
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Multicast Forwarding A Closer Look: RPF Check Succeeds Multicast Packet from Source 151.10.3.21 S0 S1
RPF Check Succeeds! Unicast Route Table Network Interface 151.10.0.0/16 S1 198.14.32.0/24 S0 204.1.16.0/24 E0
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S2 E0
Packet Arrived on Correct Interface! Forward Out All Outgoing Interfaces (i.e. Down the Distribution Tree)
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© 1999, Cisco Systems, Inc.
Multicast Distribution Trees Shortest Path or Source Distribution Tree Source Address 1.1.1.1 Group Address 224.2.2.2
Notation: (S, G) or (1.1.1.1 , 224.2.2.2) and (1.1.2.1 , 224.2.2.2) S = Source G = Group
A
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D
F
C
E
Receiver 1
Receiver 2
Source Address 1.1.2.1
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Multicast Distribution Trees Shared Distribution Tree Source Address 1.1.1.1 Group Address 224.2.2.2
Notation: (*, G) or (* , 224.2.2.2) * = All Source s G = Group
A
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D (Shared Root)
C
E
Receiver 1
Receiver 2
F
Source Address 1.1.2.1
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© 1999, Cisco Systems, Inc.
Remember the Basics • Multicast source-based routing rules Implied knowledge of sources in every router, or, some bootstrap mechanism used to provide this knowledge on-demand.
• Source-trees (S,G) • Shared-trees (*,G) • RPF—Reverse Path Forwarding 303 1011_05F9_c3
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Multicast Routing Protocols— Characteristics Needed • Unicast routing protocol-independent • Support for dense distribution of participants • Support for sparse distribution of participants • Scalability—Extensible to inter-domain multicast routing • Maturity—Widely deployed • Well-defined—RFC 303 1011_05F9_c3
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Multicast Protocol Overview • Currently, there are five multicast routing protocols: DVMRPv2 (Internet-draft) DVMRPv1 (RFC 1075) is obsolete and unused. A variant is currently implemented MOSPF (RFC 1584) PIM-SM (RFC 2362- v2) PIM-DM (Internet-draft) Others (CBT, OCBT, QOSMIC, SM, etc.) 303 1011_05F9_c3
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Dense Mode IP Multicast Protocols The Flood and Prune Method 1. Flood everywhere initially 2. Prune back where no group members 3. Prune on redundant non-shortest path 4. Periodic reflooding
Source
No Receivers A
B
Uses Shortest Path Tree
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C
E
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Dense Mode PIM Example Source
Link Data Control
A
B G
C
D
F H
E
I
Receiver 1 303 1011_05F9_c3
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Dense Mode PIM Example Source Initial Flood of Data and Creation of State A
B G D
F H
E
I
Receiver 1 303 1011_05F9_c3
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Dense Mode PIM Example Source Prune to Non-RPF Neighbor
A
B G
Prune C
D
F H
E
I
Receiver 1 303 1011_05F9_c3
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Dense Mode PIM Example Source C and D Assert to Determine Forwarder for the LAN, C Wins A
B G
C
D
F
Asserts H E
I
Receiver 1 303 1011_05F9_c3
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Dense Mode PIM Example Source I Gets Pruned E’s Prune is Ignored G’s Prune is Overridden A
B
Prune G
C
D
F
H
Prune E
I
Receiver 1 303 1011_05F9_c3
Join Override
Receiver 2
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Dense Mode PIM Example Source New Receiver, I Sends Graft
A
B G
C
D
F H
Graft E
I
Receiver 1
Receiver 2 Receiver 3
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Dense Mode PIM Example Source
A
B G
C
D
F H
E
I
Receiver 1
Receiver 2 Receiver 3
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Dense-Mode Protocols
• DVMRP Distance Vector Multicast Routing Protocol • PIM DM Protocol Independent Multicasting (Dense Mode) • MOSPF Multicast Open Shortest Path First 303 1011_05F9_c3
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DVMRP—D istance V ector DVMRP—Distance DVMRP— Vector M ulticast R outing P rotocol Multicast Routing Protocol • Unicast Protocol Dependent—requires its own RIP-like, integrated unicast routing protocol • Constructs separate distribution tree for each source/group • Uses reverse path forwarding to flood-and-prune Floods:: broadcasts packets out all outgoing interfaces on distribution tree, initially assuming every branch is part of the multicast group Prune: Eliminates tree branches without multicast group members, cutting off transmission to LANs without interested receivers, also prunes redundant non-shortest paths from any receiver to the source 303 1011_05F9_c3
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Evaluation Evaluation:: DVMRP • Most effective for dense distribution of multicast receivers • Widely used on the MBONE (being phased out) • Significant scaling problems Slow Convergence—RIP-like behavior Significant amount of multicast routing state information stored in routers—(S,G) everywhere No support for shared trees Maximum number of hops < 32
• Not appropriate for large scale networks with… Few interested receivers due to flood and prune behavior Groups sparsely represented over WAN 303 1011_05F9_c3
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MOSPF (RFC 1584) M ulticast Extension to OSPF Multicast • Extension to OSPF unicast routing protocol OSPF: Routers use link state advertisements to understand all available links in the network (route messages along least-cost paths) MOSPF: Includes multicast information in OSPF link state advertisements to construct multicast distribution trees (each router maintains an up-to-date image of the topology of the entire network)
• Group membership LSAs are flooded throughout the OSPF routing domain so MOSPF routers can compute outgoing interface lists • Uses Dijkstra algorithm to compute shortest-path tree Separate calculation is required for each source/group pair 303 1011_05F9_c3
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Evaluation Evaluation:: MOSPF • Does not flood multicast traffic everywhere to create state, Uses LSAs and the link-state database • Protocol dependent—works only in OSPF-based networks • Significant scaling problems Dijkstra algorithm run for EVERY multicast (S,G) pair! Does not support shared-trees
• Not appropriate for… Large internetworks with a large number of senders and receivers 303 1011_05F9_c3
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PIM Dense Mode • Protocol Independent Supports all underlying unicast routing protocols including: static, RIP, IGRP, EIGRP, IS-IS, BGP, and OSPF
• Uses reverse path forwarding Floods network and prunes back based on multicast group member information
• Appropriate for... Smaller implementations and pilot networks 303 1011_05F9_c3
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Evaluation Evaluation:: PIM Dense Mode • Most effective for dense distribution of multicast receivers • Advantages: Easy to configure—two commands Simple flood and prune mechanism Easy to understand and debug • Potential issues... Flood and prune behavior—WAN No support for shared trees 303 1011_05F9_c3
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Sparse-Mode Protocols
• PIM SM
Protocol Independent Multicast Sparse-Mode
• Other
CBT, OCBT, QOSMIC, etc.
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Sparse-Mode Protocols • Works for either sparse or dense groups, optimized for sparsely populated groups Explicit join behavior—assumes no one wants the packet unless they asked Uses either source or shared distribution trees Joins propagate from receiver to RP or sources. Sources are learned by first having their packets flow down the shared-tree
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Sparse Mode IP Multicast Routing Protocols Explicit Join Mechanism Source 1
1. No one receives group traffic until specific join 2. Rendezvous point queried 3. Sites pruned back permanently as needed 4. No periodic flooding as in dense-mode Rendezvous Point (Shared Root)
A
B
C
Receiver 1 303 1011_05F9_c3
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F
E
Non Viewers
Uses “Shared Tree” Initially. Can Switch over to Shortest Path Tree if Needed/Defined.
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Sparse Mode PIM Example Link Data Control
A
B
C
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RP
E
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Sparse Mode PIM Example Receiver 1 Joins Group G C Creates (*, G) State, Sends (*, G) Join to the RP
A
B
C
D
RP Join E
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Sparse Mode PIM Example RP Creates (*, G) State
A
B
D
RP
C
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Sparse Mode PIM Example Source 1 Sends Data A Sends Registers to the RP
Source 1
Register
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B
C
D
RP
E
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Sparse Mode PIM Example RP De-Encapsulates Registers Forwards Data Down the Shared Tree Sends Joins Towards the Source
Source 1
Join
A
Join
B
D
RP
C
E
Receiver 1 303 1011_05F9_c3
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Sparse Mode PIM Example RP Sends Register-Stop Once Data Arrives Natively
Source 1
Register-Stop
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B
C
D
RP
E
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Sparse Mode PIM Example C Sends (S, G) Joins to Join the Shortest Path (SPT) Tree
Source 1
A
B
D
RP
(S, G) Join C
E
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Sparse Mode PIM Example C Sends Prunes Up the RP tree for the Source. RP Deletes (S, G) OIF and Sends Prune Towards the Source
Source 1
(S, G) Prune
A
B
C
D RP (S, G) RP Bit Prune E
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Sparse Mode PIM Example New Receiver 2 Joins E Creates State and Sends (*, G) Join
Source 1
A
B
D
RP (*, G) Join
C
E
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Sparse Mode PIM Example C Adds Link Towards E to the OIF List of Both (*, G) and (S, G) Data from Source Arrives at E
Source 1
A
B
C
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RP
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Receiver 2
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Sparse Mode PIM Example Source 2 Starts Sending, D Sends Registers, RP Forwards Data to Receivers down Shared Tree
Source 1
Register
A
B
D
RP
C
E
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Receiver 2
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Sparse Mode PIM Example Source 1 RP Sends Joins to D
Register
A
B
C
Receiver 1 303 1011_05F9_c3
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Join
D
Source 2
E
Receiver 2
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Sparse Mode PIM Example Source 1
Data begins flowing to RP down SPT, RP sends Register-Stop Register-Stop
A
B
D
RP
C
E
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Source 2
Receiver 2
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Sparse Mode PIM Example Source 1
A
Both Shared Tree and SPT in use
B
C
Receiver 1 303 1011_05F9_c3
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RP
Source 2
E
Receiver 2
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Other Multicast Protocols
• Very much academic works-in-progress • Purely Power Point Protocols
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P IM Sparse Mode PIM (RFC 2362) • Supports both source and shared trees • Uses a Rendezvous Point (RP) Senders register with RP and send data through it to registered receivers Assumes no hosts want multicast traffic unless they specifically ask for it
• Appropriate for… Wide scale deployment for both densely and sparsely populated groups in the enterprise Optimal choice for sparse groups with few receivers perhaps separated by expensive WAN links 303 1011_05F9_c3
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Evaluation Evaluation:: PIM Sparse Mode • Effective for sparse or dense distribution of multicast receivers • Advantages: Traffic only sent down “joined” branches Can switch to optimal source-trees for high traffic sources dynamically Unicast routing protocol-independent Basis for MBGP and MSDP inter-domain multicast routing 303 1011_05F9_c3
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PIM Sparse-Dense Mode • Works in dense mode for groups without an active rendezvous point • Works in sparse mode for groups with an active rendezvous point • Recommended method for initial multicast rollout Use without RPs initially. Functions in dense mode Add RP(s) later. Functions in sparse mode Use “Auto RP” to minimize RP configuration task
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IP Multicast Protocol Checklist Dense Sparse Distribution Distribution
DVMRP
X X
MOSPF
X
PIM-DM
CBT PIM-SM
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X
Extensible to IDMR
X
ProtocolStandards Industry Efficient Independent Status Usage
X
X X
X
X
X
X
X
X
X
X
X X
X X
X
X
X
X
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Summary
• Multicast Applications are a reality • Multicast is an End-to-End Technology • PIM-SM is the only scaleable answer today for a Multicast Interior Gateway Protocol
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Documentation and Contact Info
• EFT/Beta Site Web Page: ftp://ftpeng.cisco.com/ipmulticast.html
• EFT/Beta Mailing List:
[email protected]
• Customer Support Mailing List:
[email protected] 303 1011_05F9_c3
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Thank You
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Please Complete Your Evaluation Form Session 303
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