Patent ID: 8213440

Claim:
A method for routing a call, the method comprising: at a network routing element separate from a number portability database and a switching office that originates a number portability query: (a) intercepting a number portability response message that includes a first location routing number (LRN) and a communications service subscriber identifier, the number portability response being generated by the number portability database in response to the number portability query and being destined for the switching office; (b) in response to intercepting the number portability response message, querying a network offload data structure located within the network routing element using the communications service subscriber identifier to obtain an Internet protocol multimedia subsystem (IMS) gateway LRN associated with the communications service subscriber identifier; (c) inserting the Internet Protocol multimedia subsystem (IMS) gateway LRN associated with the communications service subscriber identifier into the number portability response message if an entry in the network offload data structure matches the communications service subscriber identifier, wherein inserting the IMS gateway LRN includes replacing the first LRN in the number portability response message with the IMS gateway LRN; and (d) routing the number portability response message to the switching office.