Re: [Sipping] Conferencing for UAs

[Alan Johnston <[e-mail]>]

At 02:06 PM 2/24/2004 +0200, Gonzalo Camarillo wrote:
>Hello,
>
>some comments on the following draft:
>http://www.ietf.org/internet-drafts/draft-ietf-sipping-cc-conferencing-03.txt
>
>The focus of a conference returns the conference URI in the contact header 
>field of the 200 OK for the INVITE. The UAC uses this URI to SUBSCRIBE to 
>the conf package (using a new dialog)...
>
>Why are we forcing the focus to use the same URI for receiving the INVITEs 
>from all the users and for receiving the SUBSCRIBEs? I believe the 
>solution would be cleaner if we defined a new header field (e.g., 
>Associated-Conf-State) that carried a globally routable URI. The 200 OK 
>for the initial INVITE (or the INVITE in a dial-out case) would carry this 
>header field. This would keep separate the URI used for joining the 
>conference and the URI used for subscribing to the state of the conference.

Gonzalo,

This is a fundamental design decision made in SIP conferencing nearly two 
years ago, and I believe it is a good one.  A requirement for conferencing 
is that a UA must be able to find out information about a conference (by 
subscribing to the conference package, for example) by only knowing the 
conference URI.

Why is this very useful property a problem?

>This is actually the approach that the draft below follows:
>http://www.ietf.org/internet-drafts/draft-camarillo-sipping-transac-package-00.txt
>
>We define the Associated-Transactions-State to be returned, for example, 
>in the 200 OK of a MESSAGE sent to an exploder. Note that we had to create 
>this new header because MESSAGE does not carry a Contact header... 
>following the same approach in both, the conferencing work and the 
>exploders work would be good, in my opinion.

With all due respect, the exploders work should follow the approaches 
described in the conferencing work.  Note that the exploders work should 
not also contradict the XCON work in related areas, as well...

Thanks,
Alan Johnston
MCI
sip:[e-mail]


>Comments?
>
>Thanks,
>
>Gonzalo
>
>
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