When a customer changes from one service provider to another and wants to retain his/her telephone number(s), the carrier that "wins" the customer will "port" the customer’s number from the former carrier.

Coordinated order activity between the Old Network Service Provider (ONSP) and New Network Service Provider (NNSP) removes the end-user’s telephone number from one carrier's records and establishes it in the records of the other carrier, establishing a Local Routing Number (LRN) for call routing purposes.