The SIP INFO Method
RFC 2976

 
Document Type RFC - Proposed Standard (October 2000; No errata)
Obsoleted by RFC 6086
Last updated 2013-03-02
Replaces draft-ietf-mmusic-sip-info-method
Stream IETF
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IESG IESG state RFC 2976 (Proposed Standard)
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Network Working Group                                        S. Donovan
Request for Comments: 2976                                  dynamicsoft
Category: Standards Track                                  October 2000

                          The SIP INFO Method

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 (2000).  All Rights Reserved.

Abstract

   This document proposes an extension to the Session Initiation
   Protocol (SIP).  This extension adds the INFO method to the SIP
   protocol.  The intent of the INFO method is to allow for the carrying
   of session related control information that is generated during a
   session.  One example of such session control information is ISUP and
   ISDN signaling messages used to control telephony call services.

   This and other example uses of the INFO method may be standardized in
   the future.

Table of Contents

   1     Introduction................................................2
   1.1   Example Uses................................................2
   2     INFO Method.................................................3
   2.1   Header Field Support for INFO Method........................3
   2.2   Responses to the INFO Request Method........................4
   2.3   Message Body Inclusion......................................5
   2.4   Behavior of SIP User Agents.................................6
   2.5   Behavior of SIP Proxy and Redirect Servers..................6
   2.5.1 Proxy Server................................................6
   2.5.2 Forking Proxy Server........................................6
   2.5.3 Redirection Server..........................................6
   3.    INFO Message Bodies.........................................6
   4.    Guidelines for extensions making use of INFO................7
   5.    Security Considerations.....................................7
   6.    References..................................................8

Donovan                     Standards Track                     [Page 1]
RFC 2976                    SIP INFO Method                 October 2000

   7.    Acknowledgments.............................................8
   8.    Author's Address............................................8
         Full Copyright Statement....................................9

1. Introduction

   The SIP protocol described in [1] defines session control messages
   used during the setup and tear down stages of a SIP controlled
   session.

   In addition, the SIP re-INVITE can be used during a session to change
   the characteristics of the session.  This is generally to change the
   properties of media flows related to the session or to update the SIP
   session timer.

   However, there is no general-purpose mechanism to carry session
   control information along the SIP signaling path during the session.

   The purpose of the INFO message is to carry application level
   information along the SIP signaling path.

   The INFO method is not used to change the state of SIP calls, or the
   parameters of the sessions SIP initiates.  It merely sends optional
   application layer information, generally related to the session.

   It is necessary that the mid-session signaling information traverse
   the post session setup SIP signaling path.  This is the path taken by
   SIP re-INVITEs, BYEs and other SIP requests that are tied to an
   individual session.  This allows SIP proxy servers to receive, and
   potentially act on, the mid-session signaling information.

   This document proposes an extension to SIP by defining the new INFO
   method.  The INFO method would be used for the carrying of mid-call
   signaling information along the session signaling path.

   1.1 Example Uses

      The following are a few of the potential uses of the INFO message:

      - Carrying mid-call PSTN signaling messages between PSTN
        gateways.

      - Carrying DTMF digits generated during a SIP session.

      - Carrying wireless signal strength information in support of
        wireless mobility applications.

      - Carrying account balance information.

Donovan                     Standards Track                     [Page 2]
RFC 2976                    SIP INFO Method                 October 2000

      - Carrying images or other non streaming information between the
        participants of a session.

      These are just potential uses; this document does not specify such
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