RFC 3327 (rfc3327) - Page 1 of 17

Session Initiation Protocol (SIP) Extension Header Field for Registering Non-Adjacent Contacts

Network Working Group                                          D. Willis
Request for Comments: 3327                              dynamicsoft Inc.
Category: Standards Track                                   B. Hoeneisen
                                                                  Switch
                                                           December 2002


        Session Initiation Protocol (SIP) Extension Header Field
                 for Registering Non-Adjacent Contacts

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.

Abstract

   The REGISTER function is used in a Session Initiation Protocol (SIP)
   system primarily to associate a temporary contact address with an
   address-of-record.  This contact is generally in the form of a
   Uniform Resource Identifier (URI), such as Contact:
   [email protected]> and is generally dynamic and associated
   with the IP address or hostname of the SIP User Agent (UA).  The
   problem is that network topology may have one or more SIP proxies
   between the UA and the registrar, such that any request traveling
   from the user's home network to the registered UA must traverse these
   proxies.  The REGISTER method does not give us a mechanism to
   discover and record this sequence of proxies in the registrar for
   future use.  This document defines an extension header field, "Path"
   which provides such a mechanism.














Willis & Hoeneisen          Standards Track