The industry recommendation for the long-term Local Number Portability (LNP) solution is a Location Routing Number (LRN) architecture.

• Under the LRN architecture, each switch is assigned a unique ten-digit LRN, the first six digits of which identify the location of that switch (NPA/NXX). Currently, the last four digits (line number) have no significance from a routing perspective.

• These last four digits can be a dialable number in the switch, but the LRN and the dialable number have no particular relationship.

• It is important to note that the LRN is not a telephone number; it is merely the identifier of the switch to which a telephone number is ported. However, since the Numbering Plan Area (NPA) and NXX identify a particular switch, the four-digit line number may be an assigned, working telephone number in that switch.

• Each ported customer’s telephone number is matched in a regional database with the LRN for the switch that currently serves that telephone number. If the telephone number is not ported, the telephone number does not appear in the number portability database, and the call is routed to the switch that was originally assigned the NPA/NXX.