Subject: [XCON] Draft on Distributed Conferencing requirements

From: Simon Pietro Romano <[email-masked]>
Date: Thu, 25 Jan 2007 17:36:54 +0100

Dear all,

to throw a stone in the lake of discussion, I just submitted a new draft on the
"Requirements for Distributed Conferencing". It is also available at the
following site:

http://www.grid.unina.it/draft-ietf-xcon-dcon-requirements-00.txt

We know distributed conferencing is currently out-of-scope in the xcon working
group, but we'd really appreciate some feedback about it, given the fact that
the core of the work is actually represented by the XCON framework. A further
draft about the distributed conferencing framework will be available at the
same site above in the next few days.

Cheers,

Simon
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From: "Even, Roni" <[email-masked]>
Date: Thu, 25 Jan 2007 23:35:49 +0200

Simon,
I looked at the draft and am not sure what the purpose of it is.
If media mixing is out of scope so what is the conference doing.
In the scenario draft when we talk about simple cascading the idea is that each focus makes its own mixing decision without any floor control. Knowing who the participants are and the conference state by subscribing to all the focuses that compose the conference is feasible 
For the media simple cascading means that the audio mix from one focus is sent to the other as an input to the mixing decision. For the video it is even more complicated since each focus may select to display another participant if it does voice activated switching. This is why using floor control in cascaded conference makes it more predictable.
Another direction is to have distributed media using multicast.

Roni Even

> -----Original Message-----
> From: Simon Pietro Romano [mailto:[email-masked]]
> Sent: Thursday, January 25, 2007 6:37 PM
> To: XCON
> Subject: [XCON] Draft on Distributed Conferencing requirements
> 
> Dear all,
>

---

From: Lorenzo Miniero <[email-masked]>
Date: Fri, 26 Jan 2007 10:43:47 +0100

Hi Roni,

> In the scenario draft when we talk about simple cascading the idea is that each focus makes its own mixing decision without any floor control. Knowing who the participants are and the conference st…

Actually the problem in just cascading is exactly the lack of mechanisms 
as floor control. What you say is right, each focus should make its own 
mixing and exchange it with others: however, if floor control is 
involved the foci can't ignore the rights to access resources, and this 
is exactly what we want to accomplish. For example, if the floor control 
server of the focus hosting the conference (which me might improperly 
call the "main" focus) hasn't given yet the right to talk to a user 
belonging to a cascaded (or distributed) conference, the cascaded 
conference focus will have to exclude the audio of this user from its 
local mix before sharing it with others. This of course can be done only 
by an opportune dispatching of BFCP messages among the involved foci, 
which is what we envisage in our requirements thoughts. Of course the 
same considerations I just made for BFCP can be made for other XCON 
protocols (i.e. protocols that are born to live as natively centralized) 
as well, e.g. for what will be the conference control protocol. The 
distributed approach we propose is absolutely compliant with the ongoing 
work in XCON: we basically want to enable the distribution of what is 
natively centralized without "breaking" anything, and it will probably 
be much clearer once we'll release the framework draft too.

> Another direction is to have distributed media using multicast.

The fact that we consider distributed mixing out-of-scope of course 
doesn't mean we ignore it. On the contrary, we strongly believe it is of 
great importance, and this is why, as you know, we are following with 
great interest the newly born MediaCtrl WG too. However, as Eric, 
MediaCtrl's chair, noticed, distributed mixing is a very hard matter, 
and while we're studying it as a research matter (as an University, 
research is our field :) ), we thought that in a framework definition 
(and in its requirements) it would have been of greater importance 
focusing on how to distribute the involved signaling and control, and 
initially considering existing solutions for media distribution. In 
fact, in the tests we made so far this is exactly what we did: we used 
existing solutions for basic media distribution amongst the involved 
parties, e.g. BFCP-moderated exchange of all the foci's local mixes. 
While our work upon distributed conferencing and our research upon 
distributed mixing will go on, we will surely make more and more 
proposals and suggestions upon media distribution as well, but the focus 
will still remain signaling and control, as happens in XCON as well.

Best regards,
Lorenzo

-- 
Lorenzo Miniero, Junior Researcher
Dipartimento di Informatica e Sistemistica
Università degli Studi di Napoli "Federico II"
Via Claudio 21 -- 80125 Napoli (Italy)
Phone: +390817683821 - Fax: +390817683816
Email: [email-masked]

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