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Contents Chapter 5
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Introduction Three Flavors of LNP The Road to True Local Number Portability Basic LNP Networks The Terminology Before Local Number Portability Number Administration and Call Routing in the Network Location Routing Number (LRN) Using a Database Solution Triggering Mechanisms How Is a Telephone Number Ported? Other Issues Switching Systems Billing, Administration, and Maintenance Systems Signaling Operator Services 911 Services
56 56 57 59 61 62 63 63 65 66 69 70 70 70 71 71 71
Copyright 2000 The McGraw-Hill Companies. Click Here for Terms of Use.
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CHAPTER
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Local Number Portability (LNP)
Copyright 2000 The McGraw-Hill Companies. Click Here for Terms of Use.
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Introduction With the Telecommunications Act of 1996 in the United States (and the Telecom Act of 1997 in Canada), a series of competitive changes were required in the network. For years when competitors tried to compete with the Bell System, their efforts were stymied. Part of the reason was the ability to serve a new customer. Whenever the new competitor offered to serve a business or residential customer, customers were required to change their business or residential telephone number to use the new Local Exchange Carrier (LEC). Local Number Portability (LNP) is therefore an essential issue in the telephony business. Because of the need to change numbers, the incumbent LECs were able to prevent losing their customers to the competition.
Three Flavors of LNP Local Number Portability gives end users the ability to change Local Service Providers without changing their telephone numbers. Three basic forms of local number portability were introduced to the industry over the past few years: (the only one implemented is service provider portability) 1. Service provider portability allows subscribers to change Local Service Providers without changing their telephone number. This assumes that users can change suppliers and keep their existing telephone number. Still to be completed is the ability to provide LNP in a wireless world. 2. Service portability allows subscribers to change from one type of service to another (for example, analog to digital—ISDN— without changing their telephone numbers) or to be served from a different central office (where the service is available) and not have to take a new telephone number 3. Geographic portability allows subscribers to move from one physical location to another (such as state to state) without changing telephone numbers. Service provider portability was mandated by the Federal Communications Commission (FCC) in July 1996. Service provider LNP involves a circuit-switched network capability, allowing users on one switching system
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to move or port numbers to a different switching system. Congress mandated local number portability, set the regulations governing its implementation, and stated that any network modifications required to comply with these rules were the responsibility of the existing LECs. In February 1996, President Clinton signed the Telecommunications Act into law. The single most significant characteristic of the new law is that it opens the local exchange market to competition. In an effort to eliminate technical, as well as regulatory market entry barriers, the law requires that all Local Exchange Carriers (LECs)—both incumbent LECs (ILECs) and new competitive LECs (CLECs)—provide local number portability. LNP provides “users of telecommunications services with the ability to retain, at the same location, existing telecommunications numbers without impairment of quality, reliability, or convenience, when switching from one telecommunications carrier to another.”
The Road to True Local Number Portability LNP is germane to achieving true local competition. In November 1994, the industry began to seriously investigate methods of providing true Local Number Portability. While the importance of retaining a telephone number was recognized in the early 1960s, it became a significant issue associated with 1—800 (and later 1—888, 1—877 and 1—900) services during the 1980s. The need for portability among telephone companies and providers was never really an issue until the North American Numbering Plan (NANP) administration published a proposal for future numbering plans in North America. This NANP document was issued in January 1993. Of course, since that time, the level of interest has increased substantially. As equal access and competition catch up to deregulation, the use of LNP becomes critical. In late 1994, MCI commissioned a study by the Gallup Organization to assess LNP and determine the following: 1. The potential for businesses and consumers alike to switch local telephone service providers under various market scenarios. 2. The perceived importance of various service factors regarding local telephone services.
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Not surprisingly, the results of the MCI study indicated the following for residential customers: ■
Nearly 2/3 of all customers were unlikely to switch providers if given the opportunity
■
More than 3/4 stated that retaining their telephone number or numbers when switching carriers was very important.
■
80% were unlikely to switch service providers if they would have to change their telephone numbers. Moreover, business customers showed the following results:
■
57% were unlikely to switch local telephone service providers if given the opportunity.
■
83% said that retaining their telephone number or numbers when switching Local Service Providers was extremely important.
■
90% were unlikely to switch providers if they would have to change their telephone numbers.
With business customers, the cost of changing numbers can be significant. When a business changes telephone numbers, the costs include reprinting stationary, business cards, advertisements, and literature. The statistics are shown in Figure 5-1. These discussions led to an organization’s development of the Carrier Portability Code (CPC) model, which was selected by the New York State Public Utility Commission LNP task force as the architecture to be used. MCI with the support of several manufacturers demonstrated the architecture to the FCC via a live test in May of 1995 to prove that true local number portability was indeed technically feasible.
Figure 5-1 Comparison of business and residential user concerns over service provider change
100% 80% 60% 40% 20% 0%
Residential
Business
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On June 27, 1996, the FCC adopted rules on LNP. The FCC required LNP availability on a permanent basis as of October 1, 1997. This availability must be complete for the top 100 Metropolitan Statistical Areas (MSA) by December 1998. After the December 1998 dates, all LECs (ILECs and CLECs) in other areas are required to provide LNP within six months upon request. The FCC actually adopted performance criteria, rather than a specific technology to meet the need. The criteria includes the following information: ■
Support of existing services and capabilities
■
Efficient use of numbering plans
■
No change in numbers for end users
■
No requirement to rely on databases of another carrier in order to process (route) calls
■
No unreasonable degradation of service or reliability when implemented or when customers switch
■
Not resulting in any carriers’ proprietary interest
■
Ability to accommodate location and service portability in future years
■
No adverse impact outside areas where LNP is deployed
States will have flexibility if they meet the criteria listed previously. Wireless carriers have been granted a reprieve from the December dates, originally allowing a June 1999 implementation date. This has since been postponed until June 2000 and may be extended again. Shortly after the studies were completed, several states began the process of officially selecting the architecture to be used for LNP in their respective states. The Illinois task force requested LNP solutions from a wide array of companies via a Request For Proposal (RFP) developed by the carriers that offered service in the state of Illinois at that time. An official voting body, which was comprised of those carriers, was established to select the architecture. After considerable discussion and deliberation, Lucent Technologies’ Location Routing Number (LRN) architecture was selected.
Basic LNP Networks The components of LNP are not that much different from the original SS7 networks used for years. The pieces serve different functions, which you can see by looking at the following components:
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The Switching Service Point (SSP) is the local CO or tandem switching office.
■
The Signal Transfer Point (STP) is a packet mode handler that routes data queries through the signaling network.
■
The Signal Control Part (SCP) is the database for features, routing, and Global Title Translation (GTT).
■
The LSMS is the Local Service Management System; SOA is the Service Order Administration.
LSMS and SOA can be provisioned separately, but when combined it is referred to as the Number Portability Administration Center (NPAC) connectivity. For wireless providers, the LNP capabilities depend on the MSA served. Wireless providers’ schedules keep changing because of the lobbying of the CTIA. See the network overview in Figure 5-2.
Figure 5-2 Basic LNP network
Legend Signaling Trunks = Voice Trunks = SCP
Local SMS
STP 704-444
707-222
707-333
LNP Service Administration (NPAC)
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The Terminology Several terms are introduced with LNP. Some of the more common ones are as follows: Portable number A number that is permitted to move between different service provider switches Ported number A Directory Number (DN) served by a switch other than the switch that has traditionally served that number Non-ported number A Directory Number that is portable, but is currently served by the switch that is identified in the Local Exchange Routing Guide (LERG) as serving that number These three concepts are shown in Figure 5-3 depicting the terminology.
Figure 5-3 LNP terminology
Donor switch 623-555 LNP SCP
LRN-LNP SSP
Non-ported number 623-55X-1101
Originating switch
LRN-LNP SSP
ISUP Trunks
LRN-LNP SSP Recipient switch 480-777 602-7X9-1111
Ported number 623-55X-1234
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Before Local Number Portability In the earlier, non-LNP environment, a telephone number performed two functions: 1. It identified the customer. 2. It provided the network with information necessary to route a call to that customer. Local Number Portability separates these two functions, providing the means for customers to keep their Directory Number when changing Local Service Providers. By separating those two functions, LNP gives customers the flexibility to respond to pricing and service changes offered by rival carriers. As we have seen, numerous studies conclude that most business and residential customers are reluctant to switch from one service provider to another if they must change their telephone numbers. Without LNP, new entrants (CLECs) would have to price their local exchange service 12—15% lower than the existing local exchange carriers in order to persuade customers to switch carriers. Although the degree to which the lack of LNP hurts competition is arguable, it is clear that LNP is required to provide a level playing field. Interim number portability methods, such as remote call forwarding and direct inward dialing, existed but these methods have several disadvantages: ■
Longer call set-up times
■
Increased potential for call blocking
■
Continued reliance on the incumbent LEC’s network
■
Use of more directory numbers, which are fast becoming depleted
■
Loss of feature functionality
■
Substantial on-going costs to the new Local Service Provider.
According to the Telecommunications Act, LNP will promote local exchange competition, which in turn will benefit all customers. As it has done in the long distance market, competition in the local exchange market is expected to do the following: ■
Drive down the cost of service
■
Encourage technological innovation
■
Stimulate demand for telecommunications services
■
Boost United States’ economic growth
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Number Administration and Call Routing in the Network Telephone numbers in a pre-LNP environment have always been assigned to Local Service Providers’ end offices on an area code and exchange code (NPA-NXX) basis. Each NPA-NXX contains 10,000 telephone numbers. Because an NPA-NXX is only served by a single end office in the United States, the telephone number identifies the person, as well as the actual end office that serves that person. In effect, the dialed NPA-NXX is the terminating switch’s routing address to the rest of the network. With the implementation of local number portability, which allows any number of Local Service Providers to serve the same NPA-NXX, this routing scheme can no longer be used.
Location Routing Number (LRN) With LRN, every switch in the network is assigned a unique 10-digit number that is used to identify it to the rest of the network for call routing purposes. An essential advantage of the LRN is that call routing is performed based on today’s numbering format. LRN uses the strength of SS7 signaling with Multi-Frequency (MF) interworking, and promises to be a longterm solution for LNP. LNP is SS7, ISDN User Part (ISUP) oriented, and therefore does not work well with MF interworking. LRN-LNP on the Switching Service Points (SSPs) performs the integral part of the overall network LNP solution. The LRN is shown in Figure 5-2 with a new, ten-digit number assigned to the individual switching points. LRN depends on Intelligent Network (IN) or Advanced Intelligent Network (AIN) capabilities deployed by the wireline carriers’ networks. LRN is a 10-digit number to uniquely identify a switch that has ported numbers. The LRN for a particular switch must be a native NPA-NXX assigned to the service provider for that switch. LRN assigns a unique ten-digit telephone number to each switch in a defined geographic area. The LRN now serves as the network address. Carriers routing telephone calls to end users who have changed from one carrier to another (and kept their same number) perform a database dip to obtain the LRN corresponding to the dialed telephone number. The database dip is performed for all calls where the NPA-NXX of the called number has been flagged in the switch as a portable number. The carrier then routes the call to the new provider based on the LRN.
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Shown in Figure 5-4 is the flow of LRN information, which is the same for both a wireline and a wireless provider (with one modification: the JIP is not used in the wireless network and LRN flow from wireless). When the caller dials the number (333—3333 in this case), the originating switch (612—222) sends its signaling information (info dialed 333—3333) through the STP to the SCP, which analyzes the route and returns the LRN (612—444—0001). Next an IAM message is forwarded from 612—222 through the STP to the access tandem. The AT translates the LRN and sets up a speech path (trunk) from 222 to 444. Switch 612—444 detects the LRN (612— 444—0001) as its address; therefore the called number and the generic address parameter are swapped. From there, the call is connected (terminated) at 333—3333. The donor switch in this scenario has been uninvolved throughout the process. Similar to the 800-number service, a database is used to store the routing information for subscribers who have moved or ported to another Local Service Provider. The LNP database contains the directory numbers of all ported subscribers and the location routing number of the switch that serves them. The LNP database can be accessed by switches using either Advanced Intelligent Network (AIN 0.1) or Transaction Control Application Part Intelligent Network (TCAP IN) protocol. Each OLNP-capable switch in
Legend
Figure 5-4 The LRN in use
= Signaling path Recipient Switch 333-3333
= Speech Path SCP
612-444
6
LRN 612-44X-0001 detected as its own
7
CdPN & GAP swapped
8
Call terminated to 333-3333
IAM LRN (9CdPN) FCI number translated
STP
JIP (see note) 612-222
AT
GAP 612-333-3333 Analyze Route LRN = 612-44X-0001
5
AT translates on LRN, sets up path from 222 to 444 trunk
3
1 4
Info analyzed 333-3333
612-222
2
612-333 Donor switch
333-333 DN has ported
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a portability area is assigned a unique ten-digit location routing number. A switch is defined as LNP-capable if it has the capability to launch LNP database queries and route calls based on the returned response. The tendigit LRN is chosen from an NXX native to that switch (an NXX that was originally owned by that switch prior to Local Number Portability), and is used by other switches to route calls to that switch. New routing and signaling methods are required to implement this feature because the LRN architecture requires the transport of the network routing address (or LRN of the terminating switch) and the called party number. Only the Integrated Service User Part (ISUP) signaling is being modified to carry the additional information needed to support local number portability. Workarounds to use Multi-Frequency (MF) trunks, such as sending only the dialed number when a MF route is used, have been included in the requirements. The LRN feature uses the Location Routing Number returned from the LNP database to route the call and the Called Party Number to complete the call in the terminating switch. From a protocol perspective, the LRN of the end office serving the subscriber is placed into the Called Party Number field (CdPN) and the actual Called Party Number is populated in the new Generic Address Parameter (GAP) field. As the call traverses the network, all switches will use the LRN to route the call. When the call is delivered to the terminating switch, the terminating switch will compare the LRN received in the called party number field against its own LRN. If these numbers match, then the terminating switch will retrieve the called party number from the GAP parameter and complete the call to the subscriber. Once a switch performs an LNP database query, that switch must set a new bit called the Translated Called Number Indicator (TCNI) in the forward call indicator parameter of the Initial Address Message (IAM). This will indicate to other switches in the call path that a query has already been performed. This new bit, and the corresponding call-processing logic, ensures that multiple queries will not be performed for the same call.
Using a Database Solution Many carriers felt that the best way to implement LNP is to establish databases that contain the customer routing information necessary to route telephone calls to the appropriate terminating switches. The LNP database, similar to that already used by the telecommunications industry to provide 800-number portability, will use intelligent network or AIN capabilities.
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These capabilities separate the customer-identification information from the call-routing information. Rather than establishing one national database, similar to the 800-number database, carriers will provide LNP via a system of multiple, regional databases. A national LNP database is not feasible, simply because one database could not store the telephone numbers for the entire United States population or even the subset of the largest metropolitan areas. Further, a regional database system offers specific advantages for carriers deploying LNP. Regional databases effectively reduce the distance over which carriers must transmit routing information. By minimizing that distance, a regional system reduces the associated routing costs incurred by the carriers. A regional database system also ensures that carriers will have all the number portability routing information they need to route calls between carriers’ networks for that regional area. Because many of the major carriers install their own SCP where the LNP database resides, a single access point must be provided to effectively manage and distribute updates to the common regional LNP database. These updates will provide all carriers with the changes made when end users “port” from one Local Service Provider to another. Most states have decided that a Number Portability Administration Center (NPAC), similar to the arrangement used for 800-number portability, should be used. The LNP task force in Illinois issued an RFP to the industry to solicit technical (and financial) proposals for the NPAC. Lockheed-Martin was chosen to develop and administer the NPAC in Illinois. Other companies were selected by different regions, but complications arose and Lockheed-Martin was selected to replace those who could not deliver. Management of the LNP database by a third party will ensure the security of all carriers’ customer bases. The full scenario of a call process is shown in Figure 5-5, using the components of the network and the databases.
Triggering Mechanisms Using local number portability requires end office switching systems to determine if a dialed NPA-NXX has been declared open for portability. The switching systems must set triggers on a portable NPA-NXX to cause, or “trigger,” a query to the LNP database and retrieve the LRN of the dialed number. Most switching vendors are using AIN 0.1 triggers. AIN 0.1 triggers were defined by industry requirements well before the development of
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Figure 5-5 LNP scenario
MF trunk
AT
SCP 3
5
NEW LEC
SS7 trunk
2
4
EO
EO
LNP originating office
Intermediate office 1
1. Call placed to ported 2. Originating switch performs LNP 3. SCP replies 4. LNP IAM packet sent to non-LNP 5. Non-LNP tandem outpulses over MF trunk, only LRN is sent (in called party parameter), dialed number lost and call
Donor office
LNP. These triggers are administered on the NPA-NXX digit string by using the administration capabilities of the switching systems. Unconditional trigger mechanisms are used during the transition from one service provider to another, such as the following: 1. From a wireline to a wireless provider 2. From an ILEC to a CLEC 3. From a wireless to a wireline provider These triggers can be assigned at the donor switch (the old provider) and the recipient switch (the new provider). By using an unconditional trigger, the trigger is used at the switch even if the directory number is present (see Figure 5-6). The industry requirements for the location routing number model state that either a TCAP IN “800-like” or AIN 0.1 query can be used. The protocol defines the information and structure of the query between switching systems and the LNP database. Both of these protocols, defined within industry standards, are deployed in the network today. The AIN model is shown in Figure 5-7.
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SCP
10 Digit Unconditional Trigger
Donor Switch (Old LEC)
Assigned to a line during the transition from the old to new service provider (LEC).
SCP
Can be assigned at both the Donor Switch (Old LEC) and the Recipient Switch (New LEC).
612-333
Unconditional trigger: triggers at switch even if DN is present, ESCDN ignored. Subscriber 333-3333 Ports from Old LEC to New LEC
612-444 Recipient Switch (New LEC)
Old LEC Pre-SCP Update Post-SCP Update Dialed number returned, terminate on this switch (Donor)
Figure 5-7 The AIN model
LRN returned, route to New LEC (Recipient)
Legend:
Triggers at Donor or Recipient ensuring no subscriber downtime or service outage during service provider transition.
New LEC Pre-SCP Update Post-SCP Update Dialed number returned, Home LRN returned, route to (Donor) terminate on this switch switch (Recipient)
Null
= Point in call
Information attempt
= Trigger detection point Authorizing origination attempt
Collecting information
Infomation collected Analyzing information
Trigger criteria: - PODP based LNP trigger - 3 to 10 digits - Criteria checking DN residency Equal access Operator assisted Coin
Information analyzed Selecting route
Authorizing call set-up
Call proceeding
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How Is a Telephone Number Ported? Many steps are required to move or “port” an end user from one Local Service Provider to another. Database changes will be required in the following locations: ■
Old Local Service Provider’s central office
■
New CLEC central office
■
LNP database
Beyond that, the end user’s copper pair must be disconnected from the old service provider’s central office equipment and connected to the new Local Service Provider’s central office equipment or some patch field in a colocated office. All of these activities are controlled by the NPAC. Several important steps must proceed the actual porting of a subscriber: 1. The NPA-NXX must be opened for porting by the NPAC. This drives the update of the Local Exchange Routing Guide (LERG) database, global title translations in the STPs, and end-office translations (to set the LNP trigger for the NPA-NXX) for all Local Service Providers in the portability area. 2. The two service providers must arrange the physical transfer of the subscriber’s copper pair. Both providers must have implemented the 10-digit unconditional trigger function in their respective end offices. 3. Once all the pre-move actions have been performed, a subscriber can be ported. The availability of the unconditional trigger in both the new and old Local Service Provider’s end offices will preclude the need to synchronize every step of the porting process. 4. The donor switch administers the 10-digit unconditional trigger on the porting subscriber’s directory number. This will cause an LNP query under all conditions (even when the subscriber is still served by the old service provider’s end office), thereby eliminating the critical timing coordination between the donor and the recipient (new) Local Service Provider. This allows the activities at the donor switch to be performed autonomously with respect to the recipient service provider and route calls to the subscriber based on the LNP query response. 5. The recipient switch administers the translations for the new subscriber, and sets the 10-digit unconditional trigger. This allows
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the recipient switch to provision the subscriber prior to the actual physical move of that subscriber’s copper pair, without causing calls to be misrouted during that time period. As in the case of the donor switch, the 10-digit unconditional trigger also allows activities at the recipient switch to perform autonomously. 6. After the subscriber’s copper wire has been moved, the new Local Service Provider notifies the NPAC of the change. The NPAC then downloads each LNP database (in the portability area) with the LRN of the new Local Service Provider (for the ported subscriber) and records the transaction (for example, date/time). After the new Local Service Provider successfully tests the new subscriber, the unconditional trigger is removed.
Other Issues Below are but a few of the impacts that local number portability bring to the telecommunications network.
Switching Systems Substantial changes to call-processing logic and administration software is required in all switching systems in use in today’s telecommunications network in order to implement local number portability. The cost of the system upgrades and changes has been accumulated in a pool by the RBOCs and is now being passed on to consumers. The costs typically range from $.27$.54 per line per month. This pass-through cost will continue for five years (ending in 2004) as the plan calls today. Additional impacts will be evident when a Line Information Database (LIDB) requires a dip to determine the 0 plus calling card model, as shown in Figure 5-8.
Billing, Administration, and Maintenance Systems Because local number portability removes the direct association of a subscriber’s directory number to a central office, substantial changes will be required in most of the systems in use today in local telephone company networks.
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Figure 5-8 LIDB model for 0 plus calling card
708-828-2222
LNP SCP
3
7
4
9 11
10
8
STP
312-225
DMS TOPS
5
Recipient Switch LIDB 6
708-232-1111
1 708-232
A
Originating Switch
2 708-828 Donor Switch
Signaling Local number portability will require an LNP database query for every call to a ported subscriber that is not served by the originating switch. This will require capacity increases in the number of Signaling System 7 (SS7) links to the signaling transfer points, and deployment of new service control points to run the LNP database application. These costs have also been accumulated, and they are now being passed through as part of the fee discussed previously.
Operator Services Operator calls from subscribers (for example, 0-, 0, and so on) are routed directly to the operator services system where an LNP query must be performed to determine the Local Service Provider to which the call must be routed. Thus, significant modifications are required in operator services systems (see Figure 5-9).
911 Services Maintaining the 911 and enhanced 911 databases create another impact for the processing of calls to emergency response agencies. When we think about LNP in a wireline environment, the process is straightforward. The caller places an emergency call from a fixed location, which is easily identifiable. Routing of the E911 call is to the proper Public Safety Answering
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72 Figure 5-9 Operator service impacts
708-828-2222
LNP SCP 4
6
3 5 STP
312-225
DMS TOPS
Recipient Switch LIDB 708-232-1111
2
1
708-828
708-232
Donor Switch
Originating Switch
Callflow flowfor for0-Call 0-CallModel Model Call 1.1.Subscriber Subscriber708-232-1111 708-232-1111dials dials0-0-and andisisconnected connectedtotoTOPS TOPSoperator. operator. 2.2.Operator Operatorreceives receivesrequest requesttotoconnect connecttoto708-828-2222 708-828-2222and andbill billtotooriginatorís originator’sstation. station. 3.3.TOPS TOPSdetermines determinesthat thatrequested requestednumber numberhas hasbeen beenported portedand andsends sendsan anLNP LNPquery querytotoLNP LNPSCP. SCP. 4.4.LNP LNPSCP SCPresponds respondswith withthe theLRN LRN(312-225-0000) (312-225-0000)ofofRecipient RecipientSwitch. Switch. 5.5.TOPS TOPSroutes routescall calltotoRecipients RecipientsSwitch. Switch. 6.6.Recipients RecipientsSwitch Switchterminates terminatescall calltotoported portednumber number708-828-2222. 708-828-2222.
Point (PSAP), based on a known, prearranged location for each telephone. ANI is mapped one-to-one for all wireline calls by using the appropriate callback number and a location from an Automatic Location Information database (ALI). This is shown in Figure 5-10. Using CAMA trunks (trunks that were originally used for cost accounting and messaging call information), 911 routing is built on limited capability of the trunk. The CAMA trunks will remain in use for some time to come. Is 911 Important? 80,000 calls per day are made to 911 emergency locations. This places a great burden on the network.
Figure 5-10 E911 calling with LNP
911 Call Taker
* Voice and ANI Central Office
CAMA Trunks
E-911 Tandem (Selective Router) LEC
Voice and ANI PSAP
AL1 Request
Voice
Wireline Telephone Subscriber
BASIC WIRELINE CALL FLOW * Routing to correct PSAP based on known preassigned location of each telephone because ANI is one-to-one mapped to a callback number and a location. Routing tables can be very accurate in this case.
ALI Information
ALI Database
