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SIP: Session Initiation Protocol
RFC 2543

Document type: RFC - Proposed Standard (March 1999; No errata)
Document stream: IETF
Last updated: 2013-03-02
Other versions: plain text, pdf, html

IETF State: (None)
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IESG State: RFC 2543 (Proposed Standard)
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Network Working Group                                          M. Handley
Request for Comments: 2543                                          ACIRI
Category: Standards Track                                  H. Schulzrinne
                                                              Columbia U.
                                                              E. Schooler
                                                                 Cal Tech
                                                             J. Rosenberg
                                                                Bell Labs
                                                               March 1999

                    SIP: Session Initiation Protocol

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1999).  All Rights Reserved.

IESG Note

   The IESG intends to charter, in the near future, one or more working
   groups to produce standards for "name lookup", where such names would
   include electronic mail addresses and telephone numbers, and the
   result of such a lookup would be a list of attributes and
   characteristics of the user or terminal associated with the name.
   Groups which are in need of a "name lookup" protocol should follow
   the development of these new working groups rather than using SIP for
   this function. In addition it is anticipated that SIP will migrate
   towards using such protocols, and SIP implementors are advised to
   monitor these efforts.

Abstract

   The Session Initiation Protocol (SIP) is an application-layer control
   (signaling) protocol for creating, modifying and terminating sessions
   with one or more participants. These sessions include Internet
   multimedia conferences, Internet telephone calls and multimedia
   distribution. Members in a session can communicate via multicast or
   via a mesh of unicast relations, or a combination of these.

Handley, et al.             Standards Track                     [Page 1]
RFC 2543            SIP: Session Initiation Protocol          March 1999

   SIP invitations used to create sessions carry session descriptions
   which allow participants to agree on a set of compatible media types.
   SIP supports user mobility by proxying and redirecting requests to
   the user's current location. Users can register their current
   location.  SIP is not tied to any particular conference control
   protocol. SIP is designed to be independent of the lower-layer
   transport protocol and can be extended with additional capabilities.

Table of Contents

   1          Introduction ........................................    7
   1.1        Overview of SIP Functionality .......................    7
   1.2        Terminology .........................................    8
   1.3        Definitions .........................................    9
   1.4        Overview of SIP Operation ...........................   12
   1.4.1      SIP Addressing ......................................   12
   1.4.2      Locating a SIP Server ...............................   13
   1.4.3      SIP Transaction .....................................   14
   1.4.4      SIP Invitation ......................................   15
   1.4.5      Locating a User .....................................   17
   1.4.6      Changing an Existing Session ........................   18
   1.4.7      Registration Services ...............................   18
   1.5        Protocol Properties .................................   18
   1.5.1      Minimal State .......................................   18
   1.5.2      Lower-Layer-Protocol Neutral ........................   18
   1.5.3      Text-Based ..........................................   20
   2          SIP Uniform Resource Locators .......................   20
   3          SIP Message Overview ................................   24
   4          Request .............................................   26
   4.1        Request-Line ........................................   26
   4.2        Methods .............................................   27
   4.2.1      INVITE ..............................................   28
   4.2.2      ACK .................................................   29
   4.2.3      OPTIONS .............................................   29
   4.2.4      BYE .................................................   30
   4.2.5      CANCEL ..............................................   30

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