Subject: Re: [MMUSIC] The a=type attribute should not be session-level in SDP

From: Colin Perkins <[email-masked]>
Date: Tue, 02 Apr 2002 17:28:47 -0500

Hi,

--> Xiaotao Wu writes:
>One usage of the a=type attribute is to define a conference as moderated
>as `a=type:moderated'. Based on the sdp-new-07, that should indicate the
>use of a floor control tool and that the media tools are started so as to
>"mute" new sites joining the conference.
>
>A common senario of a conference is, people can always see each other, but
>only one people can talk at a time. That means audio is moderated but not
>video. When a person join the conference, the person should mute his audio
>tool but not video tool so that the other people can see him.

This is common, but not the only possible scenario.

>However, if the a=type attribute is defined as the session-level
>attribute, both the audio tool and video tool of the person will be
>muted. That's not expected. So, defining a=type attribute as session-level
>attribute cannot handle this senario.

I disagree. We don't want "a=type:moderated" to be specific to a particular
floor control policy, rather it should allow the floor control protocol the
flexibility to enforce policy as desired.  The only way this is possible is
if participants start with all media muted, and enable them only after they
have obtained permission from the moderator.

I believe sdp-new-07, and RFC 2327, are correct.

Colin

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From: Xiaotao Wu <[email-masked]>
Date: Tue, 2 Apr 2002 19:12:28 -0500 (EST)

> have obtained permission from the moderator.

Then the moderator will be very busy in a large conference. Think about a
moderated conference with audio and whiteboard. Everybody is allowed to
speak but only one people can draw on the board so that the figure will
not get messed up. If the conference server invite 500 people to join the
conference, the moderator of the conference need to grant permission 501
times when the conference starts. (500 for audio and 1 for whiteboard).
If we allow the a=type:moderated to be media level (only applied to the
whiteboard), the moderator will only need do the grant permission once to
the person who can draw on the whiteboard.

Why not allow the a=type:moderated can be both session level or media
level attribute?

-Xiaotao

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From: Colin Perkins <[email-masked]>
Date: Tue, 02 Apr 2002 22:01:06 -0500

>Why not allow the a=type:moderated can be both session level or media

It's possible, but it's a non-backwards compatible change.

Colin