Siemens HIPATH 8000 - Manual (Page 34)

Technical Overview
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Technical Overview
Session Initiation Protocol (SIP)
Overview
The Session Initiation Protocol (SIP) is a ASCII-based signalling protocol
used for establishing sessions in an IP network. A session could be a sim-
ple two-way telephone call or it could be a collaborative multi-media con-
ference session.
Like other VoIP protocols, SIP provides signaling and session management
within a packet telephony network. Signaling allows call information to be
carried across network boundaries. Session management controls the at-
tributes of an end-to-end call.
SIP was originally developed in the MMUSIC group within the IETF (Inter-
net Engineering Task Force), it has been published since February 1999 as
RFC 2543. The SIP working group is continuing to enhance the protocol
and published version 2 as RFC 3261 in 2002.
SIP Functions
Systems which use SIP are able to provide the following:
• The location of the target endpoint — SIP supports address resolution,
name mapping, and call redirection.
• The media capabilities of the target endpoint—Via Session Description
Protocol (SDP), SIP determines the lowest level of common services
between endpoints. Conferences are established using only the media
capabilities that can be supported by all endpoints.
• A session between the originating and target endpoint — If the call can
be completed, SIP establishes a session between the endpoints. SIP
also supports mid-call changes such as adding another endpoint to the
conference and changing media characteristic or codec.