Subject: [Sipping] Re: Sidebars

From: Alan Johnston <[email-masked]>
Date: Wed, 16 Jul 2003 14:01:06 -0500

At 11:09 AM 7/14/2003 -0400, Eric Burger wrote:
>[on XCON list, even though a SIPPING draft]

[Moved to SIPPING where discussion belongs]

>I still don't get the motivation, use case, or reasoning for REQ-7,8,9 
>(sidebars) in draft-ietf-sipping-conferencing-requirements-00.
>
>Why aren't sidebars different dialogs?

Eric,

When talking about sidebars, we usually have audio and video sidebars in 
mind as IM sidebars are somewhat trivial (and common).

The motivation is that many user agents only support a single dialog and 
ones that do support 2 or more dialogs treat the two dialogs as independent 
sessions (i.e. the media is never mixed and you can only work on one dialog 
at a time - the other is usually put on hold).

If the mixing is being done centrally, entering a sidebar just changes the 
mix sent to you.  In distributed mixing, a sidebar will likely result in an 
additional media stream being sent to the participant in addition to the 
other streams.  In both these cases, there is no reason (or advantage) to 
having a separate dialog.

There are some corner cases where a non-participant is invited to a sidebar 
but is not a participant in a conference - look for a discussion of these 
cases in an upcoming I-D on sidebars which is intended to help clarify some 
of these sorts of questions.

Thanks,
Alan Johnston
MCI

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