Patent ID: 8285852

Claim:
A method of operating a user terminal or IP Multimedia Subsystem (IMS) network node, said method comprising the steps of: identifying at an IMS protocol stack in the user terminal or IMS network node, a communication service corresponding to a communication service identifier contained in a received Session Initiation Protocol (SIP) message, wherein the communication service identifier is included in the SIP message as a feature tag in the SIP message header; forwarding the SIP message to the identified communication service; receiving the SIP message at the identified communication service; identifying at the identified communication service, an application corresponding to an application reference contained in the SIP message, wherein the application reference is included in the SIP message as a feature tag in the SIP message header and as an “a-line” augmenting an “m-line” in the Session Description Protocol (SDP) part of the SIP message; and forwarding the SIP message to the identified application; wherein the communication service identifier and the application reference separately identify the communication service and the application so that when multiple applications utilize a single communication service, the user terminal or IMS network node can properly route SIP messages to the identified communication service and the identified application.