Subject: RE: [Simple] IMDN issue #8: List-Action, Original-From and Original-Message-ID

From: "Burger, Eric" <[email-masked]>
Date: Thu, 2 Feb 2006 12:05:17 -0500

Yes, Original-* and List-Action could support the direct reporting from
the UAS to the UAC.  However, they are necessary to solve a thorny
problem that B2BUA's introduce.  Namely, by the strict definition of
delivery, the B2BUA MUST issue the IMDN, and that is the end of the
story.  The B2BUA has no right to request a downstream IMDN, nor does it
have the right to relay the downstream IMDN back to the Requesting UAC.

I agree the most common user interpretation of IMDN is that it is for
the final UAS, even through a gateway or exploder, to do the reporting.
HOWEVER, it is no the only case.  Given that the plan below breaks the
definition of a UAS (the UAS half of a UAC) and it does not allow users
or intelligent agents who really only care if the message was processed
at the gateway or list exploder, I would offer that we use a mechanism
that works for all scenarios.

I would also offer the mechanism proposed in the text works for all
scenarios.

[Note to Hisham - are you referring to the mechanism in
draft-burger-simple-imdn-01 or draft-ietf-simple imdn-00?  I don't think
anyone has seen draft-ietf-simple-imdn-00 yet.  The ietf-simple-imdn
mechanism is very different (although backwards compatible) with the
burger-simple-imdn mechanism.]

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf
Of Hisham Khartabil
Sent: Friday, January 27, 2006 10:19 AM
To: Simple WG
Subject: [Simple] IMDN issue #8: List-Action,Original-From and
Original-Message-ID

I don't think the List-Action header is needed. The Original-From 
header and Original-Message-ID may not be needed also. this depends on 
how we define the behaviour of the IM exploder to be.

To summarise:

- List-Action header is used to indicate if a B2BUA  or UAS is to do 
the reporting
- Original-From allows a UAS to know there to send the notification if 
there was a B2BUA like an exploder on the path.
- Original-Message-ID allows a UAS to indicate to the UAC the 
message-ID of the original message that the notification is for. This 
is also when a B2BUA is involved.

All 3 headers are above to help the case that a UAC chooses for the UAS 
to send the notifications directly instead of the B2BUA generating them 
indicating the B2BUA's receipt of the message.

I would design it as follows:

- UAC indicates, in the IM, its wish to receive an IMDN
- B2BUA forwards the IM with the necessary original-from and 
original-message-id headers (if needed)
- the UAS generates the IMDN and sends it just like it would send an IM 
to the UAC. For MSRP, it would be just like a SEND request in the other 
direction. For SIP MESSAGE, it would use the from (or original-from) 
and to headers in the incoming IM to create the MESSAGE request in the 
reverse direction. Same applies for message-id.
- If it was not possible for the B2BUA to reach the UAS, it would 
generate its own IMDNs for that IM.

Regards,
Hisham

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---

From: Hisham Khartabil <[email-masked]>
Date: Thu, 2 Feb 2006 19:43:38 +0100

> have the right to relay the downstream IMDN back to the Requesting UAC.

I disagree. That might be your definition of a B2BUA, not mine. How 
could a B2BUA issue an IMDN to a IM it has no idea if it has been 
delivered to a user or not. Especially if the IMDN is a read report.

> that works for all scenarios.

Can you give real world examples of such scenarios where the sender 
only cares that the GW or B2BUA has the message delivered to it.

> I would also offer the mechanism proposed in the text works for all

Can you describe that mechanism to folks who don't have the privilage 
of seeing the pending WG item version?

> burger-simple-imdn mechanism.]

I'm referring to burger-simple-imdn-01. We cannot just change 
mechanisms without discussion on the mailing list, especially when the 
draft is a WG item.

Thanks,
Hisham