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Managing Client-Initiated Connections in the Session Initiation Protocol (SIP)
RFC 5626

Approval announcement
Draft of message to be sent after approval:


From: The IESG <>
To: IETF-Announce <>
Cc: Internet Architecture Board <>,
    RFC Editor <>, 
    dispatch mailing list <>, 
    dispatch chair <>
Subject: Protocol Action: 'Managing Client Initiated Connections 
         in the Session Initiation Protocol (SIP)' to Proposed Standard 

The IESG has approved the following document:

- 'Managing Client Initiated Connections in the Session Initiation 
   Protocol (SIP) '
   <draft-ietf-sip-outbound-20.txt> as a Proposed Standard

This document is the product of the Dispatch Working Group. 

The IESG contact persons are Robert Sparks and Cullen Jennings.

A URL of this Internet-Draft is:

Ballot Text

Technical Summary

   This document defines an extension to the Session Initiation Protocol
   (SIP) that provides for persistent and reusable connections between
   SIP User Agents and SIP Proxy Servers. In particular, this allows
   proxy servers to initiate TCP connections or to send asynchronous UDP
   datagrams to User Agents in order to deliver requests.  However, in a
   large number of real deployments, many practical considerations, such
   as the existence of firewalls and Network Address Translators (NATs)
   or the use of TLS with server-provided certificates, prevent servers
   from connecting to User Agents in this way.  This specification
   defines behaviors for User Agents, registrars and proxy servers that
   allow requests to be delivered on existing connections established by
   the User Agent.  It also defines keep alive behaviors needed to keep
   NAT bindings open and specifies the usage of multiple connections from
   the User Agent to its Registrar.

Working Group Summary

   The working group process on this document was exceptionally long. The

   first WG version of the draft appeared in the summer of 2005. Working
   group last call initiated in the summer of 2006 and extended until the
   summer of 2008, requiring several iterations of the draft and the
   assignment of Francois Audet as a "process champion" for the draft
   within the working group. Most delays seem to have been related to
   slow cycle time on the part of the authors, but the process was also
   delayed by a number of changes occurring during the review cycle.

   Particular sticking points included the keepalive mechanism and a
   requirement for binding to multiple outbound proxies if so
   configured. Both were eventually resolved by a widely-accepted
   compromises. Additional work is being pursued in SIPCORE to allow
   the use of the keepalive mechanism independently of the outbound

Document Quality

  There have been implementations of previous versions of this 
  draft testing at SIPit events since 2005.


   Dean Willis is the document shepherd with significant assistance
   from Francois Audet. Robert Sparks is the responsible area director.

RFC Editor Note