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Re: [MMUSIC] Why do we need rtcp-mux-exclusive?

Roman Shpount <roman@telurix.com> Mon, 21 March 2016 09:59 UTC

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Date: Mon, 21 Mar 2016 05:59:55 -0400
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From: Roman Shpount <roman@telurix.com>
To: Christer Holmberg <christer.holmberg@ericsson.com>
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Cc: "mmusic@ietf.org" <mmusic@ietf.org>, Paul Kyzivat <pkyzivat@alum.mit.edu>
Subject: Re: [MMUSIC] Why do we need rtcp-mux-exclusive?
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On Mon, Mar 21, 2016 at 5:43 AM, Christer Holmberg <
christer.holmberg@ericsson.com> wrote:

> >> In my opinion, a=rtcp-mux PLUS a=rtcp with RTP port would be an easy
> was to indicate mux-exclusive, and it would work both with ICE and non-ICE.
> I don’t think we should define multiple mechanisms for doing the same thing.
> >
> >I would argue that a=rtcp is completely redundant potentially ignored
> information. It does not indicate (at least not yet) that trickle will not
> generate RTCP candidates. If ICE is used, the absence of RTCP candidates is
> enough to indicate that RTCP should not be sent yet. If ICE is not used,
> there is no grantee that a=rtcp is not ignored, so >it does not help. So,
> we can just include rtcp-mux and do not include any RTCP candidates, and we
> will get the result we need without any new specifications.
>
> How does the receiver know that RTCP candidates won’t be trickled later?
>
>
If offer contained rtcp-mux and answer specified rtcp-mux, rtcp-mux will be
used. Because of this, answerer always knows if rtcp-mux is used. Even if
RTCP candidates will be trickled later, they will not be used and can be
safely ignored.
_____________
Roman Shpount

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