Patent ID: 8266302

Claim:
A method of evaluating Initial Filter Criteria at a terminating Call Session Control Function in an IP Multimedia Subsystem network, the method comprising: receiving a Session Initiation Protocol message, the Session Initiation Protocol message including an original Request-Uniform Resource Identifier; applying an Initial Filter Criterion to the message; as a result of applying the Initial Filter Criterion to the message, sending the message to an Application Server and suspending evaluation of further Initial Filter Criteria; receiving the message returned from the Application Server; determining whether the original Request-Uniform Resource Identifier has been changed by the Application Server to a changed Request-Uniform Resource Identifier; when the original Request-Uniform Resource Identifier has been changed by the Application Server: determining whether to resume evaluation of Initial Filter Criteria; upon determining not to resume evaluation of Initial Filter Criteria, passing the message directly to outgoing message handling in the Call Session Control Function; and upon determining to resume evaluation of Initial Filter Criteria, resuming evaluation of Initial Filter Criteria utilizing the changed Request-Uniform Resource Identifier; and when the original Request-Uniform Resource Identifier has not been changed by the Application Server, resuming evaluation of Initial Filter Criteria utilizing the original Request-Uniform Resource Identifier.