IP Multimedia System Security
The IP multimedia subsystem (IMS) is a core network subsystem within UMTS. It is based on the use of the Session Initiation Protocol (SIP)26 to initiate, terminate and modify multimedia sessions such as voice calls, video conferences, streaming and chat. SIP is specified by the Internet Engineering Task Force (IETF)27. IMS also uses the IETF Session Description Protocol (SDP)28 to specify the session parameters and to negotiate the codecs to be used. SIP runs on top of different IP transport protocols such as the User Datagram Protocol (UDP) and the Transmission Control Protocol (TCP).
A 3G IMS subscriber has one IP multimedia private identity (IMPI) and at least one IP multimedia public identity (IMPU). To participate in multimedia sessions, an IMS subscriber must register at least one IMPU with the IMS. The private identity is used only for authentication purposes.
Read more about this topic: UMTS Security
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