Subject: [Sip] Connected-identity and changing the To header field in a response

From: "Elwell, John" <[email-masked]>
Date: Tue, 04 Apr 2006 07:45:33 +0100

During discussion of draft-elwell-connected-identity in Dallas, somebody put
forward the opinion that it would be dangerous to change the To header field
URI in a response (i.e., make it different from the From header field URI in
the request). My assumption at the time was that it would undermine the
transaction concept in SIP, yet reading what RFC3261 has to say about
transactions, the value of the To header field URI in a response does not
appear to be involved in coupling a response to a request. Therefore I
assume the person who indicated the danger (which was not challenged at the
meeting) has other reasons in mind. I would greatly appreciate opinions on
the wisdom or otherwise of allowing the To header field URI to change. It
seems that from discussion of connected-identity there is a desire from some
parts of the community to include an (unauthenticated) identity in a
response.

John

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From: "Bob Penfield" <[email-masked]>
Date: Tue, 4 Apr 2006 07:58:17 -0400

The issue with changing the To in a response is backward compatibility with 
RFC 2543 which does use the To for transaction matching. RFC 2543 section 
1.4.3 says:

   All responses to a request contain the same values in
   the Call-ID, CSeq, To, and From fields (with the possible
   addition of a tag in the To field (section 6.37)).
   This allows responses to be matched with requests.

cheers,
(-:bob

Robert F. Penfield
Chief Software Architect
Acme Packet, Inc.
71 Third Avenue
Burlington, MA 01803
[email-masked]

----- Original Message ----- 
From: "Elwell, John" <[email-masked]>
To: <[email-masked]>
Sent: Tuesday, April 04, 2006 2:45 AM
Subject: [Sip] Connected-identity and changing the To header field in 
aresponse

> parts of the community to include an (unauthenticated) identity in a

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