In an LNP environment, it can no longer be assumed that the NPA/NXX code holder actually serves the end user.

• During call setup, an LNP database in the Signaling System 7 (SS7) network is queried to determine which switch actually serves the dialed number.

• If the number is ported, the Called Party Number (CdPN) field is moved into the Generic Address Parameter (GAP) field, and the LRN information is overlaid in the CdPN field so the call can be routed to the proper terminating switch.

• The terminating switch then completes the call to the end user based on the data contained in the GAP.