RFC 2976 (rfc2976) - Page 2 of 9

The SIP INFO Method

Alternative Format: Original Text Document
< Previous
Next >
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
< Previous
Next >