Patent ID: 7761600

Claim:
A method of distributing application server addresses in an IP multimedia subsystem, the method comprising the steps of: receiving a Session Initiation Protocol (SIP) request associated with a subscriber at a Serving Call Session Control Function (S-CSCF), the SIP request including a subscriber identity; in response to receiving the SIP request at the S-CSCF, selecting an application server by the S-CSCF and forwarding the SIP request to the selected application server; in response to receiving the SIP request at the selected application server, dynamically allocating the subscriber to the selected application server and sending the subscriber identity and at least one application server address from the selected application server to a Home Subscriber Server (HSS) associated with the subscriber thereby registering as the subscriber's serving application server; in response to receiving the at least one application server address at the HSS, storing the at least one address at the HSS in association with the subscriber identity for responding to future subscriber-related messages; sending the at least one application server address from the HSS to the S-CSCF, wherein if an explicit address has been allocated, the allocated explicit address is sent to the S-CSCF by the HSS, and if no explicit address has been allocated, the HSS sends to the S-CSCF a generic application server identity and the S-CSCF resolves the received generic identity to one of a plurality of explicit addresses; and caching the at least one address at the S-CSCF in association with the subscriber identity, wherein the S-CSCF utilizes the at least one address to send subscriber-related messages to the allocated application server.