Subject: [Sipping] comments on draft-loreto-sipping-context-id-requirements

From: Jonathan Rosenberg <[email-masked]>
Date: Sun, 27 Jul 2008 18:30:41 -0400

Thanks for putting this together.

My main comment, as Paul has made on the list as well, is that the use 
cases seem really varied. They cover what, to me, seemed like three 
different problem spaces:

a. correlating together multiple dialogs that need to be viewed as a 
single conversation, possibly due to multi-device issues

b. solving the problem of 'escalating' from a pager mode IM conversation 
to a proper IM session mode

c. correlating new dialogs with dialogs that happened previously

I think these are pretty different problems, and need to be considered 
separately. I'm not at all convinced that a new identifier is the right 
idea at all for (c), for example; using a URI and then sending an INVITE 
to that URI was discussed as a solution for that. In some respects, the 
draft reads like, "well, if we had a correlation ID, here is what we 
could do with it". I think the draft needs to take a step back and focus 
on one of the key areas.

I do think there is some value in correlating together dialogs (problem 
A). I'm not at all convinced about this idea of my camera itself having 
a sip stack. However, a case where I have a desk phone in my office, and 
a PC with a softclient, and I'd like the video on my PC and the audio on 
my deskphone - that is a more likely use case than the camera with 
video. There had been some debate about alternative models, where its 
more like device control than a peer UA that gets REFERed into a new 
dialog. I suspect the camera case is much more likely to be device 
control; but cases like the above are much easier to realize via a 
peer-oriented REFER.

So my suggestion would be to try and more fully enumerate cases where we 
need (a), as I suspect there are others.

-Jonathan R.

-- 
Jonathan D. Rosenberg, Ph.D.                   499 Thornall St.
Cisco Fellow                                   Edison, NJ 08837
Cisco, Voice Technology Group
[email-masked]
http://www.jdrosen.net                         PHONE: (408) 902-3084
http://www.cisco.com
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