Subject: [Sipping] Distributing "requests" to call/conference participants

From: Bob Gaglianello <[email-masked]>
Date: Fri, 11 Feb 2005 11:08:27 -0500

Hello,

I posted this on the MMUSIC mailing list and I have not received any 
response. So, I thought I would try the SIPPING group.

I am looking for guidance as to what is an “appropriate” or “acceptable” 
mechanism for signaling all the SIP clients within a call/conference to 
“start-up” an additional conferencing application such as a shared 
presentation tool or a shared Web Browser. I assume all clients have the 
ability to execute the app and have a copy to execute on their local 
machine. I need some way of distributing a message like: “Start up 
conferencing application XYZ”. This needs to work for two parties in a 
point-to-point call as well as a multiple parties connected through a 
conference bridge.

I would greatly appreciate any help and thoughts on this.

Cheers,
Bobg

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From: "Brian Rosen" <[email-masked]>
Date: Fri, 11 Feb 2005 11:50:55 -0500

There is no such mechanism standardized.

If there is to be one, it would probably be handled in xcon

If you are inventing a proprietary one, and you insist on a SIP mechanism,
then I think you either put an extension to the conference package, or a new
header (P-Associated-Application).  If the "app" was a URI, that's easy.  A
real app implies some kind of name space.  I don't really think it's a media
thing, so it's not SDP.

Brian

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf
> Of Bob Gaglianello
> Sent: Friday, February 11, 2005 11:08 AM
> To: [email-masked]
> Subject: [Sipping] Distributing "requests" to call/conference participants
> 
> Hello,
> 
> I am looking for guidance as to what is an "appropriate" or "acceptable"
> "start-up" an additional conferencing application such as a shared
> machine. I need some way of distributing a message like: "Start up
> conferencing application XYZ". This needs to work for two parties in a

---

From: Scott Lawrence <[email-masked]>
Date: Fri, 11 Feb 2005 13:15:20 -0500

> point-to-point call as well as a multiple parties connected through a 

I think that what you really want to announce is that there is new media
being added to the conference - a re-INVITE with new SDP.  Choosing the
application to deal with that media is not the business of the
conference - it's the responsibility of the endpoint.

-- 
Scott Lawrence <[email-masked]>

---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 11 Feb 2005 13:16:57 -0500

Bob,

I think it depends a bit on what you are trying to do.

If you are trying to say "ok, now we have gotten to the boring part of 
the meeting, so I want all of you to bring up Solitare and occupy 
yourselves", then I think there is no way, and no reason for one.

But I suspect you have in mind an application that is interactive among 
all the members of the conference. That implies some interaction among 
the application instances running for each participant. And that 
interaction requires some sort of protocol.

In a sip conferencing environement I think it would be most appropriate 
to add a media stream to the conference, offering it to all the 
participants. The media stream would represent the protocol for the 
application interaction. It would then be up to each pariticipant to 
either accept or reject the offered media stream. If accepted, it would 
then presumably figure out which application it requires in order to 
handle that media stream.

	Paul

---

From: Bob Gaglianello <[email-masked]>
Date: Mon, 21 Feb 2005 15:42:07 -0500

Hello again,

Thanks for the responses to my previous posting concerning distribution 
of  “requests” to call/conference participantsI received one suggesting 
Subscribe/Notify and two suggesting a re-INVITE/SDP implementation.

I have some questions concerning the SDP approach in the presence of a 
conference bridge/focus (the conference bridge includes an “audio mixing 
entity” that can transcode between various voice codecs, i.e g.711 and 
g.729).

Assume a conference is in progress and one of the participants requests 
a codec change through a reINVITE/SDP. According to 
“draft-ietf-sipping-conferencing-framework-03,” section 5.7, a 
conference focus should generate reINVITEs to all the participants when 
media are being added or removed from a given conference.

I this case, shouldn’t the bridge just make the change between the 
“mixing element” and the originator instead of sending out reINVITEs to 
all the participants?

Using the above scenario again, assume that a participant would like to 
add video to the conference and change the audio codec at the same time. 
Should the focus transmit the video request to all the participants and 
make the voice codec change “local” or request all the participants to 
change their voice codec? The first requires the focus to make changes 
to the SDP in the reINVITE before sending it to the other participants 
and the latter does not.

Is there some criterion on when a focus retransmits, changes or keeps 
local reINVITE/SDP messages or is it “application/implementation” dependent?

Now assume a participant requests the other participants to “start-up” 
an additional application using a reINVITE/SDP and a given participant 
rejects the new media. Does that information get signaled to the 
originator and if so how?

cheers,
bobg

>> I am looking for guidance as to what is an “appropriate” or 
>> “acceptable” mechanism for signaling all the SIP clients within a 
>> call/conference to “start-up” an additional conferencing application 
>> such as a shared presentation tool or a shared Web Browser. I assume 
>> all clients have the ability to execute the app and have a copy to 
>> execute on their local machine. I need some way of distributing a 
>> message like: “Start up conferencing application XYZ”. This needs to 
>> work for two parties in a point-to-point call as well as a multiple 
>> parties connected through a conference bridge.
>>