rfc3261 session initiation protocol (sip) extension.txt

有关IMS SIP及Presence应用的RFC文档包

Network Working Group                                       J. Rosenberg
Request for Comments: 3261                                   dynamicsoft
Obsoletes: 2543                                           H. Schulzrinne
Category: Standards Track                                    Columbia U.
                                                            G. Camarillo
                                                                Ericsson
                                                             A. Johnston
                                                                WorldCom
                                                             J. Peterson
                                                                 Neustar
                                                               R. Sparks
                                                             dynamicsoft
                                                              M. Handley
                                                                    ICIR
                                                             E. Schooler
                                                                    AT&T
                                                               June 2002

                    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 (2002).  All Rights Reserved.

Abstract

   This document describes Session Initiation Protocol (SIP), an
   application-layer control (signaling) protocol for creating,
   modifying, and terminating sessions with one or more participants.
   These sessions include Internet telephone calls, multimedia
   distribution, and multimedia conferences.

   SIP invitations used to create sessions carry session descriptions
   that allow participants to agree on a set of compatible media types.
   SIP makes use of elements called proxy servers to help route requests
   to the user's current location, authenticate and authorize users for
   services, implement provider call-routing policies, and provide
   features to users.  SIP also provides a registration function that
   allows users to upload their current locations for use by proxy
   servers.  SIP runs on top of several different transport protocols.



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RFC 3261            SIP: Session Initiation Protocol           June 2002


Table of Contents

   1          Introduction ........................................    8
   2          Overview of SIP Functionality .......................    9
   3          Terminology .........................................   10
   4          Overview of Operation ...............................   10
   5          Structure of the Protocol ...........................   18
   6          Definitions .........................................   20
   7          SIP Messages ........................................   26
   7.1        Requests ............................................   27
   7.2        Responses ...........................................   28
   7.3        Header Fields .......................................   29
   7.3.1      Header Field Format .................................   30
   7.3.2      Header Field Classification .........................   32
   7.3.3      Compact Form ........................................   32
   7.4        Bodies ..............................................   33
   7.4.1      Message Body Type ...................................   33
   7.4.2      Message Body Length .................................   33
   7.5        Framing SIP Messages ................................   34
   8          General User Agent Behavior .........................   34
   8.1        UAC Behavior ........................................   35
   8.1.1      Generating the Request ..............................   35
   8.1.1.1    Request-URI .........................................   35
   8.1.1.2    To ..................................................   36
   8.1.1.3    From ................................................   37
   8.1.1.4    Call-ID .............................................   37
   8.1.1.5    CSeq ................................................   38
   8.1.1.6    Max-Forwards ........................................   38
   8.1.1.7    Via .................................................   39
   8.1.1.8    Contact .............................................   40
   8.1.1.9    Supported and Require ...............................   40
   8.1.1.10   Additional Message Components .......................   41
   8.1.2      Sending the Request .................................   41
   8.1.3      Processing Responses ................................   42
   8.1.3.1    Transaction Layer Errors ............................   42
   8.1.3.2    Unrecognized Responses ..............................   42
   8.1.3.3    Vias ................................................   43
   8.1.3.4    Processing 3xx Responses ............................   43
   8.1.3.5    Processing 4xx Responses ............................   45
   8.2        UAS Behavior ........................................   46
   8.2.1      Method Inspection ...................................   46
   8.2.2      Header Inspection ...................................   46
   8.2.2.1    To and Request-URI ..................................   46
   8.2.2.2    Merged Requests .....................................   47
   8.2.2.3    Require .............................................   47
   8.2.3      Content Processing ..................................   48
   8.2.4      Applying Extensions .................................   49
   8.2.5      Processing the Request ..............................   49



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   8.2.6      Generating the Response .............................   49
   8.2.6.1    Sending a Provisional Response ......................   49
   8.2.6.2    Headers and Tags ....................................   50
   8.2.7      Stateless UAS Behavior ..............................   50
   8.3        Redirect Servers ....................................   51
   9          Canceling a Request .................................   53
   9.1        Client Behavior .....................................   53
   9.2        Server Behavior .....................................   55
   10         Registrations .......................................   56
   10.1       Overview ............................................   56
   10.2       Constructing the REGISTER Request ...................   57
   10.2.1     Adding Bindings .....................................   59
   10.2.1.1   Setting the Expiration Interval of Contact Addresses    60
   10.2.1.2   Preferences among Contact Addresses .................   61
   10.2.2     Removing Bindings ...................................   61
   10.2.3     Fetching Bindings ...................................   61
   10.2.4     Refreshing Bindings .................................   61
   10.2.5     Setting the Internal Clock ..........................   62
   10.2.6     Discovering a Registrar .............................   62
   10.2.7     Transmitting a Request ..............................   62
   10.2.8     Error Responses .....................................   63
   10.3       Processing REGISTER Requests ........................   63
   11         Querying for Capabilities ...........................   66
   11.1       Construction of OPTIONS Request .....................   67
   11.2       Processing of OPTIONS Request .......................   68
   12         Dialogs .............................................   69
   12.1       Creation of a Dialog ................................   70
   12.1.1     UAS behavior ........................................   70
   12.1.2     UAC Behavior ........................................   71
   12.2       Requests within a Dialog ............................   72
   12.2.1     UAC Behavior ........................................   73
   12.2.1.1   Generating the Request ..............................   73
   12.2.1.2   Processing the Responses ............................   75
   12.2.2     UAS Behavior ........................................   76
   12.3       Termination of a Dialog .............................   77
   13         Initiating a Session ................................   77
   13.1       Overview ............................................   77
   13.2       UAC Processing ......................................   78
   13.2.1     Creating the Initial INVITE .........................   78
   13.2.2     Processing INVITE Responses .........................   81
   13.2.2.1   1xx Responses .......................................   81
   13.2.2.2   3xx Responses .......................................   81
   13.2.2.3   4xx, 5xx and 6xx Responses ..........................   81
   13.2.2.4   2xx Responses .......................................   82
   13.3       UAS Processing ......................................   83
   13.3.1     Processing of the INVITE ............................   83
   13.3.1.1   Progress ............................................   84
   13.3.1.2   The INVITE is Redirected ............................   84



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   13.3.1.3   The INVITE is Rejected ..............................   85
   13.3.1.4   The INVITE is Accepted ..............................   85
   14         Modifying an Existing Session .......................   86
   14.1       UAC Behavior ........................................   86
   14.2       UAS Behavior ........................................   88
   15         Terminating a Session ...............................   89
   15.1       Terminating a Session with a BYE Request ............   90
   15.1.1     UAC Behavior ........................................   90
   15.1.2     UAS Behavior ........................................   91
   16         Proxy Behavior ......................................   91
   16.1       Overview ............................................   91
   16.2       Stateful Proxy ......................................   92
   16.3       Request Validation ..................................   94
   16.4       Route Information Preprocessing .....................   96
   16.5       Determining Request Targets .........................   97
   16.6       Request Forwarding ..................................   99
   16.7       Response Processing .................................  107
   16.8       Processing Timer C ..................................  114
   16.9       Handling Transport Errors ...........................  115
   16.10      CANCEL Processing ...................................  115
   16.11      Stateless Proxy .....................................  116
   16.12      Summary of Proxy Route Processing ...................  118
   16.12.1    Examples ............................................  118
   16.12.1.1  Basic SIP Trapezoid .................................  118
   16.12.1.2  Traversing a Strict-Routing Proxy ...................  120
   16.12.1.3  Rewriting Record-Route Header Field Values ..........  121
   17         Transactions ........................................  122
   17.1       Client Transaction ..................................  124
   17.1.1     INVITE Client Transaction ...........................  125
   17.1.1.1   Overview of INVITE Transaction ......................  125
   17.1.1.2   Formal Description ..................................  125
   17.1.1.3   Construction of the ACK Request .....................  129
   17.1.2     Non-INVITE Client Transaction .......................  130
   17.1.2.1   Overview of the non-INVITE Transaction ..............  130
   17.1.2.2   Formal Description ..................................  131
   17.1.3     Matching Responses to Client Transactions ...........  132
   17.1.4     Handling Transport Errors ...........................  133
   17.2       Server Transaction ..................................  134
   17.2.1     INVITE Server Transaction ...........................  134
   17.2.2     Non-INVITE Server Transaction .......................  137
   17.2.3     Matching Requests to Server Transactions ............  138
   17.2.4     Handling Transport Errors ...........................  141
   18         Transport ...........................................  141
   18.1       Clients .............................................  142
   18.1.1     Sending Requests ....................................  142
   18.1.2     Receiving Responses .................................  144
   18.2       Servers .............................................  145
   18.2.1     Receiving Requests ..................................  145



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   18.2.2     Sending Responses ...................................  146
   18.3       Framing .............................................  147
   18.4       Error Handling ......................................  147
   19         Common Message Components ...........................  147
   19.1       SIP and SIPS Uniform Resource Indicators ............  148
   19.1.1     SIP and SIPS URI Components .........................  148
   19.1.2     Character Escaping Requirements .....................  152
   19.1.3     Example SIP and SIPS URIs ...........................  153
   19.1.4     URI Comparison ......................................  153
   19.1.5     Forming Requests from a URI .........................  156
   19.1.6     Relating SIP URIs and tel URLs ......................  157
   19.2       Option Tags .........................................  158