Re-INVITE and Target-Refresh Request Handling in the Session Initiation Protocol (SIP)
RFC 6141

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Internet Engineering Task Force (IETF)                 G. Camarillo, Ed.
Request for Comments: 6141                                   C. Holmberg
Updates: 3261                                                   Ericsson
Category: Standards Track                                         Y. Gao
ISSN: 2070-1721                                                      ZTE
                                                              March 2011

             Re-INVITE and Target-Refresh Request Handling
                in the Session Initiation Protocol (SIP)

Abstract

   The procedures for handling SIP re-INVITEs are described in RFC 3261.
   Implementation and deployment experience has uncovered a number of
   issues with the original documentation, and this document provides
   additional procedures that update the original specification to
   address those issues.  In particular, this document defines in which
   situations a UAS (User Agent Server) should generate a success
   response and in which situations a UAS should generate an error
   response to a re-INVITE.  Additionally, this document defines further
   details of procedures related to target-refresh requests.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc6141.

Camarillo, et al.            Standards Track                    [Page 1]
RFC 6141                Re-INVITE Handling in SIP             March 2011

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Camarillo, et al.            Standards Track                    [Page 2]
RFC 6141                Re-INVITE Handling in SIP             March 2011

Table of Contents

   1. Introduction ....................................................3
   2. Terminology .....................................................4
   3. Changing the Session State during a Re-INVITE ...................5
      3.1. Background on Re-INVITE Handling by UASs ...................5
      3.2. Problems with Error Responses and Already Executed Changes .9
      3.3. UAS Behavior ..............................................10
      3.4. UAC Behavior ..............................................11
      3.5. Glare Situations ..........................................11
      3.6. Example of UAS Behavior ...................................12
      3.7. Example of UAC Behavior ...................................14
      3.8. Clarifications on Canceling Re-INVITEs ....................17
   4. Refreshing a Dialog's Targets ..................................17
      4.1. Background and Terminology on a Dialog's Targets ..........17
      4.2. Background on Target-Refresh Requests .....................17
      4.3. Clarification on the Atomicity of Target-Refresh Requests .18
      4.4. UA Updating the Dialog's Local Target in a Request ........19
      4.5. UA Updating the Dialog's Local Target in a Response .......19
      4.6. A Request Updating the Dialog's Remote Target .............19
      4.7. A Response Updating the Dialog's Remote Target ............20
      4.8. Race Conditions and Target Refreshes ......................20
      4.9. Early Dialogs .............................................21
   5. A UA Losing Its Contact ........................................21
      5.1. Background on Re-INVITE Transaction Routing ...............22
      5.2. Problems with UAs Losing Their Contact ....................22
      5.3. UAS Losing Its Contact: UAC Behavior ......................22
      5.4. UAC Losing Its Contact: UAS Behavior ......................23
      5.5. UAC Losing Its Contact: UAC Behavior ......................24
   6. Security Considerations ........................................24
   7. Acknowledgements ...............................................24
   8. References .....................................................25