Number Portability

Ported Numbers Can Cause Calls to be Misrouted

Telephone service providers are assigned telephone numbers in blocks of 10,000 or 1000 numbers each. The service providers use these blocks of numbers to provide ten digit telephone numbers to individual subscribers. When a telephone service provider is assigned a block of numbers, the service provider is the “carrier of record” for those telephone numbers in the Local Exchange Routing Guide (LERG). In 1996 the FCC ordered that telephone companies must let subscribers switch service providers and keep their telephone number. When you switch phone companies and keep your telephone number, your number is ported to the new service provider and added to the number portability database. The ported telephone number remains listed in the LERG with the carrier of record that initially received the number, but the ported number is matched with the Location Routing Number (LRN) of the new service provider in the Number Portability Adminstration Center (NPAC). The NPAC is the FCC-sanctioned organization to manage the central database of all ported telephone numbers. Today, every call in North America starts with a query to the NPAC database to determine if the telephone number has been ported to a different service provider. If the number has been ported, then the NPAC returns the Location Routing Number (LRN) for the ported number. The call is then routed using the LRN, not the dialed telephone number.

Today there are 197 million ported telephone numbers in North America. TransNexus customers report that 40% of their calls are to ported telephone numbers. This development has a dramatic impact on least cost routing. If least cost routing is based on the dialed telephone number then 40% of all calls will not be routed to the lowest cost provider! TransNexus customers have found that number portability correction can decrease their total termination costs by over 15%.