Local Number Portability (LNP) is the ability of a telephone customer in the U.S. to retain their local phone number if they switch to another local telephone service provider. The Telecommunications Act of 1996 required that the local exchange carriers (LECs) in the 100 largest metropolitan markets provide this capability by the end of 1998. The idea is that by removing the personal inconvenience of having to get a new phone number when changing service providers, competition among providers will be increased. LNP is one of the prices that local carriers must pay in order to be allowed to compete as well in the long-distance market.
LNP is made possible by the Location Routing Number (LRN). In the future, phone number portability may be extended so that customers can retain their phone number when they move to another locality. LNPs and LRNs are supervised by the Number Portability Administration Center operated by NeuStar, Inc. under the appointment of the Federal Communications Commission (FCC). When a customer moves their local service to a competitive local exchange carrier (CLEC), a new LRN is assigned to the telephone number being ported. Each local exchange and long distance carrier needs to know what that new LRN is so when someone in an another area dials the number being ported, the carrier knows what LRN to route to. This is accomplished through Local Service Management System (LSMS) databases distributed among the exchange carriers. The NPAC updates all of these databases with the newly assigned LRN. Thus, when the call is made from another area, that carrier refers to its LSMS database to obtain the current LRN for the number dialed.
The FCC mandated that by November 24, 2003, all wireless service providers had to implement wireless number portability, which allows mobile customers to retain the same phone number when they change service providers. A further development, wireline-to-wireless number portability, will allow wireline telephone customers to retain their numbers when they switch to a wireless carrier.