Location Routing Number
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A Location Routing Number (or LRN) is a unique number that uses the format of a telephone number, but actually represents an entire telephone switch through which multiple telephone numbers are routed. The assignment of a location routing number to telephone numbers allows for local number portability.
In the US, the LRN is a 10-digit number following the North American Numbering Plan (NANP). The LRN is stored in a database called a Service Control Point (SCP) that identifies a switching port for a local telephone exchange. Using LRN, when a phone number is dialed, the local telephone exchange queries or "dips" a routing database, usually the SCP, for the LRN associated with the subscriber. The LRN removes the need for the public telephone number to identify the local exchange carrier. If a subscriber changes to another telephone service provider, the current telephone number can be retained, and only the LRN needs to be changed. In addition to supporting service provider phone number portability, an LRN also supports the possibility of two other types of number portability: service portability (for example, ordinary service to ISDN) and geographic portability.
In 1996, the US Congress mandated a change in local telephone service that allows any carrier to enter a local market. The new regulation provides for local number portability (LNP), which means that when a consumer’s phone service is moved from one service provider to another, the telephone number (TN) does not change. This process is called porting a number. Every ported TN must have an LRN assigned to it. Individual TNs are mapped to an LRN (the mapping of TNs to an LRN is referred to as a ‘subscription’.)
Virginia-based NeuStar (acting as a neutral party) has been chartered with developing and maintaining the Number Portability Administration Center (NPAC) to support the implementation of Local Number Portability (LNP).
- "How LNP Works". Neustar. Retrieved 2012-06-18.
- Foster, Mark D.; McGarry, Tom; Yu, James (2003). "Number Portability in the Global Switched Telephone Network (GSTN): An Overview". RFC 3482. RFC Editor. ISSN 2070-1721.