Message Handling in an IP Multimedia Subsystem

Abstract

A method and apparatus for handling a Session initiation Protocol communication in an IP Multimedia Subsystem (IMS) network. A Proxy Call Session Control Function receives a Session Initiation Protocol message sent from a trusted remote network. The P-CSCF adds to the message a further header, which identifies a Public User Identity of a trusted entity located in the remote network served by a Serving Call Session Control Function in the IMS network. The message is then sent to the S-CSCF. The S-CSCF, and any other node that the message is sent to, knows from the presence of the further header to use the Public User Identity of the trusted entity to determine the served user rather than the P-Asserted Identity contained in the SIP message.

1 . A method of handling a Session Initiation Protocol communication within an IP Multimedia Subsystem network, the method comprising:
 at a Proxy Call Session Control Function, receiving a Session Initiation Protocol message sent from a remote network;   at the Proxy Call Session Control Function, adding to the message a further header, the further header identifying a Public User Identity of a trusted entity in the remote network served by a Serving Call Session Control Function; and   sending the message to the Serving Call Session Control Function.