Session Initiation Protocol (SIP) Response Code for Indication of Terminated Dialog
RFC 6228

Internet Engineering Task Force (IETF)                       C. Holmberg
Request for Comments: 6228                                      Ericsson
Category: Standards Track                                       May 2011
ISSN: 2070-1721

          Session Initiation Protocol (SIP) Response Code for
                    Indication of Terminated Dialog

Abstract

   This specification defines a new Session Initiation Protocol (SIP)
   response code, 199 Early Dialog Terminated, that a SIP forking proxy
   and a User Agent Server (UAS) can use to indicate to upstream SIP
   entities (including the User Agent Client (UAC)) that an early dialog
   has been terminated, before a final response is sent towards the SIP
   entities.

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/rfc6228.

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
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   described in the Simplified BSD License.

Holmberg                     Standards Track                    [Page 1]
RFC 6228                           199                          May 2011

Table of Contents

   1. Introduction ....................................................2
   2. Terminology .....................................................4
   3. Applicability and Limitation ....................................4
   4. User Agent Client Behavior ......................................4
   5. User Agent Server Behavior ......................................6
   6. Proxy Behavior ..................................................7
   7. Backward Compatibility ..........................................9
   8. Usage with SDP Offer/Answer .....................................9
   9. Message Flow Examples ...........................................9
      9.1. Example with a Forking Proxy that Generates 199 ............9
      9.2. Example with a Forking Proxy that Receives 200 OK .........10
      9.3. Example with Two Forking Proxies, of which One
           Generates 199 .............................................11
   10. Security Considerations .......................................12
   11. IANA Considerations ...........................................13
      11.1. IANA Registration of the 199 Response Code ...............13
      11.2. IANA Registration of the 199 Option-Tag ..................13
   12. Acknowledgements ..............................................13
   13. References ....................................................14
      13.1. Normative References .....................................14
      13.2. Informative References ...................................14

1.  Introduction

   As defined in RFC 3261 [RFC3261], a Session Initiation Protocol (SIP)
   early dialog is created when a non-100 provisional response is sent
   to the initial dialog initiation request (e.g., INVITE, outside an
   existing dialog).  The dialog is considered to be in early state
   until a final response is sent.

   When a proxy receives an initial dialog initiation request, it can
   forward the request towards multiple remote destinations.  When the
   proxy does that, it performs forking [RFC3261].

   When a forking proxy receives a non-100 provisional response, or a
   2xx final response, it forwards the response upstream towards the
   sender of the associated request.  After a forking proxy has
   forwarded a 2xx final response, it normally generates and sends
   CANCEL requests downstream towards all remote destinations where it
   previously forked the request associated with the 2xx final response
   and from which it has still not received a final response.  The
   CANCEL requests are sent in order to terminate any outstanding early
   dialogs associated with the request.

Holmberg                     Standards Track                    [Page 2]