Re: [rtcweb] draft-ietf-rtcweb-jsep-05 - common attributes

Justin Uberti <juberti@google.com> Mon, 04 November 2013 06:43 UTC

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From: Justin Uberti <juberti@google.com>
Date: Sun, 3 Nov 2013 22:43:25 -0800
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To: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: Re: [rtcweb] draft-ietf-rtcweb-jsep-05 - common attributes
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On Fri, Nov 1, 2013 at 2:18 PM, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:

> Section 5.2.1 says:
>
>    Each m= section, provided it is not being bundled into another m=
>    section, MUST generate a unique set of ICE credentials and gather its
>    own unique set of ICE candidates.  Otherwise, it MUST use the same
>    ICE credentials and candidates that were used in the m= section that
>    it is being bundled into.
>
> But the use of common ICE candidates for bundled m-lines doesn't work
> until it is known that bundling will be used. Seems like a few more words
> about that are called for.
>

Sure. When I say "bundled" here, I mean that the actual bundling has
occurred, i.e. the streams will be sent over the same transport (in which
case they have to use the same ICE info).

>
> Further on:
>
>    Attributes that are common between all m= sections MAY be moved to
>    session-level, if desired.
>
> I presume this is only trying to point out a common feature of SDP. But it
> overstates the real situation. This may only be done for media level
> attributes (not source level), and only those that are defined to also be
> valid at session level as a default for media level.
>
> It might be better to just not say this. Or refer to 4566 for details.
>

Since this section mentions which specific attributes must be added to each
m= section, this is just pointing out that it is also OK if these are added
at session level. But I see that not all attributes are defined as being
valid at session level, regardless of whether the values are common.

I think it is worth mentioning what JSEP endpoints should do here. Assuming
we want to permit this behavior, it sounds like we should simply mention
that this can be done only for media-level attributes that are also defined
to be valid at session-level.

>
>         Thanks,
>         Paul
>
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