Overview: Illuminet Telecommunications

Understanding Local Number Portability

Twenty years ago, consumers had few options when it came to telephone service providers. Much like their counterparts of the same era, the public utilities and telephone companies were not chosen but signed up with. Consequently, the services offered were limited to whatever the given local providers was capable of providing.

Since that time, the long distance market has opened up to competition, and now the local exchange markets are open, as well. The restrictions on competition for local and long distance telephone service no longer exist, which allows local and long distance telephone companies to compete in local markets.

Service providers who want to compete in local markets must meet certain requirements. Among these requirements is local number portability, commonly referred to as LNP.

LNP refers to the ability of consumers to keep their existing telephone numbers when they change local telephone service providers or move to a new location within a defined zone of portability.

Historically, all telephone numbers within a numbering plan area exchange (NPA-NXX) belonged to a single telephone switch. With LNP, an individual telephone number within an NPA-NXX can be moved to a different telephone switch. As a result, the NPA-NXX no longer uniquely identifies the switch that serves the telephone number.

To identify the switch, a ported number is assigned a 10-digit location routing number (LRN). Instead of the NPA-NXX, the LRN is used to route calls to the appropriate switch.