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Technical overview, Session initiation protocol (sip), Overview – Siemens HIPATH 8000 User Manual

Page 34: Sip functions, Overview sip functions

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Technical Overview

34

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.