Subject: I-D ACTION:draft-henrikson-sip-original-dialog-id-01.txt

From: [email-masked]
Date: Wed, 08 May 2002 07:29:04 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: Private SIP Extension for Original Dialog Identifier
	Author(s)	: E. Henrikson
	Filename	: draft-henrikson-sip-original-dialog-id-01.txt
	Pages		: 8
	Date		: 07-May-02
	
This document proposes a private SIP extension header used in 
conjunction with INVITE requests to provide a mechanism by which a 
stateful proxy may associate an INVITE request processed earlier 
with the INVITE request that is being currently processed. The 
association is needed by the Serving Call Session Control Function 
(S-CSCF) from the Third Generation Partnership Project (3GPP) 
architecture to ensure proper routing of an INVITE request with 
3GPP Application Servers (AS). A S-CSCF may route an INVITE request 
to multiple AS, as indicated by a subscriber profile, and each AS 
may be a B2BUA. The S-CSCF needs to keep track of each AS contacted 
and know that an incoming INVITE request is related to a previous 
outgoing INVITE request such that each AS may receive the INVITE 
request before it is sent on towards the intended destination. When 
a B2BUA AS is  involved, there is currently not a way to associate 
the incoming INVITE request with the previously sent INVITE request 
at the S-CSCF. The P-Original-Dialog-ID header provides a way to 
accomplish this association. The same mechanism may be applied to 
any SIP method that is used to initiate a dialog.

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