PDF of this tutorialThe government has defined and mandated three basic types of number portability: service provider portability, location portability, and service portability. The three types may be combined to form variations on NP services.
Service Provider Portability
Service provider portability, as defined in the Telecommunications Act of 1996, is the ability of end users to retain, at the same location, existing directory numbers as they change from one service provider to another. Historically, all directory numbers (DNs) in one NPA–NXX were assigned to a single telephone switch. The incumbent had a significant advantage in retaining customers by controlling or in effect, owning the customer’s telephone number. If a customer wanted to change local service providers, he or she was faced with the significant inconveniences of a new phone number, including distributing the new number to all of his or her family, friends, and business contacts. So, in order to facilitate competition at the local exchange, the FCC mandated that all numbers be portable to all local-exchange competitors (ILECs, CLECs, cellular, etc.).
With the introduction of service provider portability, individual DNs in one NPA–NXX may be moved to a different telephone switch. Therefore, the first six digits of a DN (NPA–NXX) will no longer uniquely identify the switch that serves that customer. In order to now identify the correct switch, the concept of a location routing number (LRN) was introduced by industry experts and approved by the FCC. Each switch that hosts portable numbers will have a 10-digit LRN assigned to it that will be used in routing a call to that switch.
The order calls for porting only within a rate center. A rate center, or the “portability domain,” is an area (usually under the jurisdiction of the state Public Utilities Commission) in which DNs can be ported. All LNP–capable network elements, including service switching points (SSPs), mobile switching centers (MSCs), signal transfer points (STPs), and signal control points (SCPs), will maintain a list of NPA–NXXs that are considered portable.
Location Portability
Location portability, as defined in the First Report & Order, Docket No. 95-116, is the ability of users of telecommunications services to retain existing directory numbers without impairment of quality, reliability, or convenience when moving from one physical location to another. In this case, a given telephone number can be associated with any network termination device, independent of location.
Location will allow customers to take their DN when they move to another geographic location outside of the original rate center. In the Second Memorandum Opinion and Order on Reconsideration regarding FCC Docket 95-116, the FCC concluded that nothing in the Act would preclude them from mandating location portability in the future; however, they had no plans to address location portability at this time.
Service Portability
Service portability, as defined in the First Report & Order, Docket No. 95-116, released July 2, 1996, is the ability of users of telecommunications services to retain existing directory numbers without impairment of quality, reliability, or convenience when switching from one service to another service provided by the same telecommunications carrier. The FCC is not addressing service portability at this time and requirements for service portability are still undefined.
