Re: [MMUSIC] [rtcweb] Quick comments on draft-roach-rtcweb-glareless-add-00

Paul Kyzivat <pkyzivat@alum.mit.edu> Fri, 10 May 2013 21:20 UTC

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Date: Fri, 10 May 2013 17:20:02 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Cc: "rtcweb@ietf.org" <rtcweb@ietf.org>, "mmusic@ietf.org" <mmusic@ietf.org>
Subject: Re: [MMUSIC] [rtcweb] Quick comments on draft-roach-rtcweb-glareless-add-00
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On 5/10/13 2:37 AM, Stefan Håkansson LK wrote:
...
> But I can easily think of other situations that would lead to glare for
> Plan A.
>
> Just as an example, think about a conference scenario with a centralized
> node. Now, one of the participants wants to mute her/his audio, and as a
> result the audio m-line would go from sendrecv to recvonly. At roughly
> the same time the server wants to disable the high res video and enable
> the low res video (because this user will be moved, based e.g. on the
> recent audio activity, from being displayed in the main video window to
> be in a thumbnail on the screen of the other participants in the
> conference), so it wants to manipulate the direction attribute of other
> m-lines.
>
> So there would be two offers sent at roughly the same time, which means
> we would have glare.

What do you mean by "roughly"?

How long does it take to do an O/A exchange that doesn't require human 
input? Presumably less than a second, maybe considerably less. (Or will 
it be more with RTCWEB and web servers in the path?)

What is the probability that the other side, for independent reasons, 
decides to make a change within that interval? (And it isn't really the 
whole interval - it is only the first part of it.)

There may indeed be realistic cases for glare, but they will probably be 
because both changes are keyed to a common event.

	Thanks,
	Paul