Re: AW: AW: [Sip] Extension of conference procedures

Hi Jerry,

please see my comments in line.

2007/9/12, Jerry Yin <jerry.yin@yahoo.com>:
>
> I think there are two ways to invoke a conference. One is to invoke the
> conference by the conference server. The other is ad-hoc conference invoked
> by the participants. The
> draft-ietf-sip-uri-list-conferencing was trying to solve
> the problem by initiating a conference from the server.
> Here's what I think for the ad-hoc conference.
> Participants: A calls B (a UA or a conference room) and put B on-hold, and
> then A calls C. Now A presses the conf button.
> 1. If B has a conference room url, A will transfer C to B (by REFER), as
> some of you discussed already. It actually is supported by some companies
> already as I know.
> 2. But if B is a UA, when the conf button is pressed, the only SIP messages
> send out by A is the re-Invite (off-hold) to B since most SIP phones support
> 3-way conference locally. Then A will do the audio mixing locally. So far I
> didn't find any solution to transfer the local 3-way conference to a
> centralized conference yet. Currently in our system, we adopted the "Join"
> header (RFC3911). When A sends the re-Invite to B, it also includes a Join
> header contains the C's dialog info. The B2B server will translate the Join
> to a centralized conference. It will Invite C with a Replace header to

[Peili] Solution 2 is interesting, but as my interpretation of
RFC3911, it seems join header should only be added in a new INVITE. I
copy the text here "The UAC places the Call-ID, to-tag, and from-tag
information for the target dialog in a single Join  header field and
sends the new INVITE to the target."

> replace the session between A and C. C will sends a BYE to A. The server
> will update the media to A and B (reInvite). Then all three parties are in
> the centralized conference room.
> I hope the new RFC for conference also capture the behavior described in 2.
> Whether it's Join header or something else. The user should be able to call
> someone first and then decided to setup a conference.Jerry
>

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