Subject: Questions.2.2

From: [email-masked] (Lawrence Conroy)
Date: Mon, 30 Aug 1999 13:52:33 +0100

Hi all (yet again),
Herewith the second bit of comment that I hope we can agree on. If not,
please holler (as if I needed to ask :).
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This bit is from my reading of SIP. It's not specific to PINT, but as we
don't suggest that PINT differs from this, I guess that it applies.

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In terms of session identifiers, the SIP part of messages of a SIP
Invitation includes (CallID+CSeq, From and To), whilst the SDP part of
these messages includes an SDP global-session-id in the o= field.

If a SIP Invitation includes a Contact: header for a third party node in an
ACK, then that third party can close the SIP INVITEd session by sending a
BYE with the same To and CallID headers, but with the From: header set to
the value indicated in the earlier Ack Contact: field.

Interestingly enough, it seems to me that the first INVITEr cannot close
the session using the original identifiers sent in its initial INVITE, as
the (CallID, From and To) tuple stored by the remote UAS is that of the the
Contact-ed third party.
The INVITEr might be able to close the session by sending a BYE with these
new (CallID, From, and To) values, however; the choice on whether or not to
accept what are now third party messages is up to the recipient.

The global-session-id may be used to identify multiple INVITations to the
same conference (it says in RFC2543).
----
Still agreed?

All the best, Lawrence
-----------------------------------------------------------------------
| Lawrence Conroy,    | "These Opinions must be mine, 'cos if they    |
| Roke Manor Research |  were my Company's they'd charge you for them"|
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This message came from the IETF PINT Working Group Mailing List.

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From: Jonathan Rosenberg <[email-masked]>
Date: Mon, 30 Aug 1999 15:43:42 -0400

> please holler (as if I needed to ask :).

This is not standard SIP behavior so far as I know. The To, From and
Call-ID must match those of the original invite, with the possible
addition of a tag in the To field. I am not aware of any place in the
SIP spec where it says to place the address in a Contact header into the
From field. 

-Jonathan R.

-- 
Jonathan D. Rosenberg                       Lucent Technologies
Member of Technical Staff                   101 Crawfords Corner Rd.
High Speed Networks Research                Holmdel, NJ 07733
FAX:   (732) 834-5379                       Rm. 4C-526
EMAIL: [email-masked]
URL: http://www.cs.columbia.edu/~jdrosen

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