Re: [MMUSIC] BUNDLE: mandate RTP/RTCP multiplexing?

Paul Kyzivat <pkyzivat@alum.mit.edu> Tue, 07 May 2013 18:36 UTC

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Date: Tue, 07 May 2013 14:36:36 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: Re: [MMUSIC] BUNDLE: mandate RTP/RTCP multiplexing?
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I'd just like to point out that AFAIK bundling doesn't *require* ICE.
So lets not make any assumptions that assume ICE is used.

	Thanks,
	Paul

On 5/6/13 2:00 PM, Dale R. Worley wrote:
>> From: Bernard Aboba <bernard_aboba@hotmail.com>
>>
>>> But it doesn't seem that there is much to gain by mandating rtcp-mux
>>> in the first offer/answer, the one where actual bundling is not being
>>> done.  All of the RTP/RTCP routing code that is active at that point
>>> has to support non-rtcp-mux operation already.
>>
>> [BA]  Support for rtcp-mux in the first offer/answer is mandated by
>> RFC 5761 Section 5.1.3:
>>     The initial SDP offer MUST include this
>>     attribute at the media level to request multiplexing of RTP and RTCP
>>     on a single port.
>
> I don't see how 5761 mandates that a=rtcp-mux MUST be used in the
> first offer of a bundle negotiation.  The context of your quote is:
>
>     5.1.3.  Interactions with ICE
>     [...]
>     If it is desired to use both ICE and multiplexed RTP and RTCP, the
>     initial offer MUST contain an "a=rtcp-mux" attribute to indicate that
>     RTP and RTCP multiplexing is desired and MUST contain "a=candidate:"
>     lines for both RTP and RTCP along with an "a=rtcp:" line indicating a
>     fallback port for RTCP in the case that the answerer does not support
>     RTP and RTCP multiplexing.  This MUST be done for each media where
>     RTP and RTCP multiplexing is desired.
>
> That is, if the device desires to use both ICE and multiplex, it has
> to use a=rtcp-mux in the first offer of ICE's set of offers.  But
> we're talking about bundling, which (in the current design) contains
> *two* ICE cycles, since the second offer (in the bundle spec) is going
> to restart ICE.  And the device need not "desire" to use "both ICE and
> multiplexed RTP and RTCP" during the first of the ICE cycles.
>
> Dale
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