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Feature Article
October 2001

VoIP Signaling Solutions: Local Number Portability


The biggest post-deregulation barrier to competition in the public telephone network was viewed as the reluctance of subscribers to change their phone number when contemplating a move to a competitive service provider. Local
number portability (LNP) is the industry's solution to that challenge. By allowing subscribers to keep their existing number when changing service providers, geographic locations, or service plans, it is hoped that competition will flourish as customers shop around for better deals and more advanced service offerings. LNP is among the largest and most complex projects ever undertaken in the public switched telephone network (PSTN). Furthermore, the introduction of mobile LNP in 2002 is set to compound the infrastructure and management costs of deploying what is, in effect, a non-revenue-generating service that increases customer churn.

LNP has emerged as a legal and competitive requirement in many international markets, including the United States. (In fact, the FCC has mandated a November 2002 deadline for wireless LNP in North America.) Currently LNP solutions are in various stages of deployment worldwide, but the cost and difficulty of deploying the service in traditional circuit-switched environments has been much greater than many carriers anticipated. This article examines the business case for deploying LNP on an IP-based infrastructure rather than a traditional Intelligent Network architecture, highlighting the substantial cost savings and time-to-market advantages of the IP-based approach. The industry-wide cost of number portability is estimated at between 25 and 30 U.S. dollars per number ported. IP-based solutions are expected to reduce this cost by up to 10 times. Since the provision of the LNP service is mandated in many countries, a more cost-effective solution is urgently required.

In launching LNP services, carriers can choose between deploying their own solution or outsourcing the service to an LNP service provider on a per transaction basis or other agreed upon pricing scheme. This method offsets the cost of developing and deploying an LNP solution but impacts the carrier's revenue after expenses. With over half of the calls placed in 2001 requiring an LNP dip, and growth expected to reach almost two-thirds of all calls by 2003, outsourcing LNP is becoming prohibitively expensive. However, implementing LNP for a carrier means implementing a service that effectively enables customers to move to a rival network. Hence it is in the carrier's interest to utilize their LNP solution to also provide enhanced services that encourage customers not to port to an alternative service provider. For example, using the LNP infrastructure to provide a unified numbering service across networks such as wireless/mobile, IP and fixed line, and Centrex would enable carriers to leverage their investment in LNP to generate new revenues and increase customer loyalty. As new services are added, they are integrated into the existing routing and subscriber databases by a unified deployment and management system.

Local number portability was introduced to Local exchange carriers in North America with the U.S. 1996 Telecommunications Act, which mandated compliance with Federal Communications Commission (FCC) recommendations governing the porting of subscriber numbers. In Europe, LNP has been driven by "directives" laid out by the Commission of the European Union. By allowing new competitive carriers to provide service to customers without forcing them to change their phone number, LNP is seen as a major vehicle for "leveling the playing field" between incumbent and new operators.

As the telecommunications market becomes more competitive, it is likely that subscribers will switch networks more often in search of enhanced services and better rates. It is, therefore, important that the infrastructure is capable of handling large numbers of simultaneous call queries in a reliable manner. Performance, scalability, reliability, and manageability are all key factors in evaluating LNP solutions.

Four of the more important elements that make up core LNP infrastructure are the master local number portability database; local-service management system; service order administration; and the LNP server.

Master Local Number Portability Database: The authoritative database containing information relating to numbers that have been ported. Information in this database is downloaded to the individual carrier's local LNP systems. In North America, this database is known as the Number Portability Administration Center, or NPAC. The NPAC is divided into regions roughly analogous to the regions covered by the Regional Bell Operating Companies.

Local-Service Management System (L-SMS): The L-SMS provides the administrative interface between the authoritative number portability database and the carrier's local number portability solution. Initially, a bulk download of the master LNP database is performed and updates are then fed to the carrier systems as they are received from each carrier's service order administration system. The L-SMS also provides number verification and other services such as number range splitting, a technique that allows specific area/exchange codes to be split between exchanges, allowing network capacity to be increased.

Service Order Administration (SOA): The SOA provides the administrative interface between carrier networks and the master LNP database. When a subscriber changes their service provider and ports their number, it is the SOA system that ensures that the change is propagated to the master database.

LNP Server: The LNP server is the central component in the IP-based LNP architecture. The LNP server provides a high-performance, highly reliable and scalable interface to the network elements that require LNP service. The LNP server utilizes a high-performance, in-memory database in order to support many thousands of queries per second from multiple network elements. It is important that the LNP server is designed to scale to support an LNP lookup for virtually every call placed with a database supporting hundreds of millions of numbers.

By using an open interface based on CORBA, it is possible to provide integration to L-SMS and master LNP databases containing different record formats. This is critically important as solutions deployed in different regions and markets depend on different number plans and in some cases require country-specific mandatory fields for administrative or legal purposes. The ability of the in-memory database solution to evolve to meet varied market requirements is a big advantage to carriers who operate on a global scale.

In order to meet scalability requirements and prevent looped-back calls in the PSTN, it is often desirable for carriers to be able to override the results of an LNP query. It is also desirable for carriers to apply different routing rules for incoming calls on specific trunks. Policies can be defined in a standard logical programming language and deployed to ensure that only optimal routes are selected for calls, based on network-specific parameters and carrier-specific business rules. The integrated service management systems can provide this in almost real-time in the IP network. In contrast, it can take many hours to update traditional switch route tables.

Network Interfaces
Network interfaces usually represent a bottleneck in traditional intelligent network (SCP/STP) solutions. By performing minimal processing on the network interface, an IP-based LNP solution can eliminate the bottleneck problem. It is also possible to go beyond the traditional TCAP interface supported by legacy systems to provide SIP and ENUM interfaces. These standard open interfaces facilitate the integration of new network elements and help us move towards real network convergence. Using an IP-based LNP solution, it is possible to provide LNP service across both fixed and wireless networks as well as networks supporting IP endpoints that are addressable via E.164 telephone numbers.

Based on current legislation, it is expected that Wireless LNP will become mandatory in November of 2002. An IP-based LNP solution allows carriers
to prepare for this event by providing seamless connectivity to the existing Mobile Switching Center (MSC) infrastructure. The utilization of SIP (the call control protocol for 3G networks) will also ensure that the chosen solution is future-proofed and will not require forklift upgrades as carriers roll out feature-rich network solutions. The high-performance database architecture can also be used to provide other advanced services on the same platform. These include line database (LIDB), voice VPN, 800/900 number translation, and inter-carrier routing services.

Long and expensive development cycles are common in the telephony industry. Carriers have long complained of closed proprietary interfaces that require millions of dollars and many months of development in order to add new features. The advantages of converged network infrastructure have been well documented in terms of cost savings from a development, deployment, and management perspective. The number of programmers available to develop and support applications based on standard interfaces far exceeds the number who are developing on any vendor-specific platform. By providing an IP-based LNP service on the same infrastructure as say 800/900 and inter-carrier routing services, cost savings can be realized from a management perspective. Today many carriers run multiple networks, voice, data, SS7, intelligent networks, and each has their own management requirements and peculiarities. By providing all services over an IP core, carriers are well positioned to take advantage of economies of scale.

IP-based LNP provided by an open standard-based infrastructure provides carriers flexibility in terms of choosing and integrating platforms and applications from multiple vendors. Open standards remove the carrier's dependence on specific vendors and platforms and free operators from the dictatorial upgrade and development cycles. Carriers can therefore create best-of-breed solutions.

Very-high-performance computing platforms that utilize the latest in processor and peripheral technologies, such as the advances in memory resident databases, free carriers to ride the technology and performance curve. Platform advances offering double the performance-per-dollar in traditional Intelligent Network Systems occur on average every 60 months compared to standard microprocessor advances every 18 months. Many legacy systems have today reached the limits of their original architecture. High-performance distributed networks are seen as the way to provide services as we move forward.

IP-based LNP solutions will offer carriers high-performance, highly reliable and manageable solutions for the deployment of LNP. Through the use of gateways to other networks, the same LNP solution can be used across a service provider's network infrastructure (wireless/mobile, PSTN, and IP). The cost benefits associated with IP-based telephony infrastructure including management, footprint, power usage, hardware, and software compared to legacy solutions and the opportunity to integrate a solution across networks make it an obvious choice for carriers. To put the cost of deploying LNP into perspective, in the 18 months that precede wireless LNP deployment in North America, carriers will invoke resources on the same scale as those that were required to prepare for Y2K conversion. Only by exploiting the existing PSTN infrastructure and combining the technology with new, leading edge concepts from the Internet and data world will carriers be able to compete in the marketplace of the future.

Nick Walker is product marketing manager for SS8 Networks. SS8 Networks provides a signaling and service infrastructure designed to enable service providers to build next-generation Intelligent Network (IN) services.

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