Correct Transaction Handling for 2xx Responses to Session Initiation Protocol (SIP) INVITE Requests
RFC 6026

Internet Engineering Task Force (IETF)                         R. Sparks
Request for Comments: 6026                                       Tekelec
Updates: 3261                                           T. Zourzouvillys
Category: Standards Track                                          Skype
ISSN: 2070-1721                                           September 2010

             Correct Transaction Handling for 2xx Responses
          to Session Initiation Protocol (SIP) INVITE Requests

Abstract

   This document normatively updates RFC 3261, the Session Initiation
   Protocol (SIP), to address an error in the specified handling of
   success (2xx class) responses to INVITE requests.  Elements following
   RFC 3261 exactly will misidentify retransmissions of the request as a
   new, unassociated request.  The correction involves modifying the
   INVITE transaction state machines.  The correction also changes the
   way responses that cannot be matched to an existing transaction are
   handled to address a security risk.

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/rfc6026.

Sparks & Zourzouvillys       Standards Track                    [Page 1]
RFC 6026         Correct Handling for SIP 2xx Responses   September 2010

Copyright Notice

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   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Conventions and Definitions .....................................3
   3. Reason for Change ...............................................3
   4. Summary of Change ...............................................4
   5. Consequences if Not Implemented .................................4
   6. The Change ......................................................4
   7. Change Details ..................................................5
      7.1. Server Transaction Impacts .................................5
      7.2. Client Transaction Impacts .................................9
      7.3. Proxy Considerations ......................................10
   8. Exact Changes to RFC 3261 ......................................11
      8.1. Page 85 ...................................................11
      8.2. Page 107 ..................................................11
      8.3. Page 114 ..................................................11
      8.4. Pages 126 through 128 .....................................12
      8.5. Pages 134 to 135 ..........................................15
      8.6. Page 136 ..................................................15
      8.7. Page 137 ..................................................17
      8.8. Page 141 ..................................................17
      8.9. Page 144 ..................................................18
      8.10. Page 146 .................................................18
      8.11. Page 265 .................................................18
   9. IANA Considerations ............................................18
   10. Security Considerations .......................................19
   11. Acknowledgments ...............................................20
   12. Normative References ..........................................20

Sparks & Zourzouvillys       Standards Track                    [Page 2]
RFC 6026         Correct Handling for SIP 2xx Responses   September 2010

1.  Introduction

   This document describes an essential correction to the Session
   Initiation Protocol (SIP), defined in [RFC3261].  The change
   addresses an error in the handling of 2xx class responses to INVITE
   requests that leads to retransmissions of the INVITE being treated as