The scope for this technical specification is to specify the security features and mechanisms for secure access to the IM
subsystem (IMS) for the 3G mobile telecommunication system.
Since the scope also encompasses the use of these security features and mechanisms for secure access to IMS in the
context of fixed broadband networks and 3GPP2 networks, Annex L and Annex S specify how the material in the main
body and other normative Annexes of this document apply to the fixed broadband networks and 3GPP2 networks respectively. The IMS supports IP Multimedia applications such as video, audio and multimedia conferences. SIP, Session Initiation Protocol, was chosen as the signalling protocol for creating and terminating Multimedia sessions, cf. RFC 3261 [6]. This specification only deals with how the SIP signalling is protected between the subscriber and the IMS, how the subscriber is authenticated and how the subscriber authenticates the IMS.