Session Initiation Protocol (SIP) Session Timer Glare Handling
draft-ietf-sipcore-sessiontimer-race-00

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Last updated 2017-10-04
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SIPCORE Working Group                                        C. Holmberg
Internet-Draft                                                  Ericsson
Updates: 4028 (if approved)                              October 4, 2017
Intended status: Standards Track
Expires: April 7, 2018

     Session Initiation Protocol (SIP) Session Timer Glare Handling
                draft-ietf-sipcore-sessiontimer-race-00

Abstract

   This document updates RFC 4028, by clarifying the procedures for
   negotiating usage of the Session Initiation Protocol (SIP) session
   timer mechansim, in order to avoid a race condition where both
   endpoints trigger simultaneous negotiations.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 7, 2018.

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   Copyright (c) 2017 IETF Trust and the persons identified as the
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Holmberg                  Expires April 7, 2018                 [Page 1]
Internet-Draft             Session timer glare              October 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Problem Statement . . . . . . . . . . . . . . . . . . . .   2
     1.2.  Solution  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Update to RFC 4028  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Update to Section 7.2 . . . . . . . . . . . . . . . . . .   3
     3.2.  Update to Section 7.4 . . . . . . . . . . . . . . . . . .   4
     3.3.  Update to Section 8.1 . . . . . . . . . . . . . . . . . .   5
     3.4.  Update to Section 9 . . . . . . . . . . . . . . . . . . .   6
   4.  Security considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Change log  . . . . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Normative references  . . . . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   [RFC4028] defines a mechanism, where periodic SIP requests are sent
   in order to allow SIP user agents and proxies to determine whether a
   SIP session is still active.

   The usage of the mechanism is negotiated using two new SIP header
   fields (Session-Expires and Min-SE), a new option tag ('timer') and a
   new SIP response code (422).

1.1.  Problem Statement

   1.  Section 7.4 of [RFC4028] says that, in a session refresh request
   sent within a dialog with an active session timer, the Session-
   Expires header field should be included in the request.  However, the
   text is unclear regarding including the Session-Expires header field
   in a session refresh request when a negotiation of session timer
   usage is still ongoing, e.g., if one user agent is sending a request
   that contains a Session-Expires header field and, before it receives
   the associated 2xx response, receives a request from the peer user
   agent that also contains a Session-Expires header field.  Such
   scenario might cause a glare situation, with conflicting negotiation
   parameters.

   2.  The absence of the Session-Expires header field in a 2xx response
   to an (re-)INVITE request [RFC3261] or UPDATE request [RFC3311] means
   that the mechanism isn't used.  This can be used to reject the usage
   of the mechanism when sending a response.  However, the text is
   unclear that this only applies to cases where the associated SIP
   request contained a Session-Expires header field.
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