Session Timers in the Session Initiation Protocol (SIP)
RFC 4028

Approval announcement
Draft of message to be sent after approval:

From: The IESG <iesg-secretary@ietf.org>
To: IETF-Announce <ietf-announce@ietf.org>
Cc: Internet Architecture Board <iab@iab.org>,
    RFC Editor <rfc-editor@rfc-editor.org>, 
    sip mailing list <sip@ietf.org>, 
    sip chair <sip-chairs@tools.ietf.org>
Subject: Protocol Action: 'Session Timers in the Session 
         Initiation Protocol (SIP)' to Proposed Standard 

The IESG has approved the following document:

- 'Session Timers in the Session Initiation Protocol (SIP) '
   <draft-ietf-sip-session-timer-16.txt> as a Proposed Standard

This document is the product of the Session Initiation Protocol Working 
Group. 

The IESG contact persons are Allison Mankin and Jon Peterson.

A URL of this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-sip-session-timer-16.txt

Technical Summary
 
   This document defines an extension to the Session Initiation Protocol
   (SIP).  This extension allows for a periodic refresh of SIP sessions
   through a re-INVITE or UPDATE request. The refresh allows both 
   user agents and proxies to determine if the SIP session is still active 
   (primarily to decide whether to clean up state associated with it).
   The extension defines two new header fields, Session-Expires, which
   conveys the lifetime of the session, and Min-SE, which conveys the
   minimum allowed value for the session timer.  It advises for a usage of
   thirty minutes for the minimum at this time, and it recommends use of
   the session timer extension the sips URI (TLS is used for each hop) 
   so that a hacker cannot lower the timer and minimum.

Working Group Summary
 
  There was strong support for this document by the working group.  The
   function is important to SIP because of  stateful proxies and forking,
   it had been handled ad hoc.  The draft was one of the earliest ones of 
   the WG.  It was delayed waiting for an extensive revision to comply
   with RFC 3261.
  
Protocol Quality

   The draft had a thorough review on the working group mailing list.  Some
    implementations are in development.  It was reviewed for the IESG by
    Allison Mankin.