Re: [MMUSIC] bundle-11: BUNDLE accpeted, but RTCP Mux rejected

"Stach, Thomas" <thomas.stach@unify.com> Wed, 08 October 2014 10:06 UTC

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From: "Stach, Thomas" <thomas.stach@unify.com>
To: Christer Holmberg <christer.holmberg@ericsson.com>, Harald Alvestrand <harald@alvestrand.no>, "Cullen Jennings (fluffy)" <fluffy@cisco.com>
Thread-Topic: bundle-11: BUNDLE accpeted, but RTCP Mux rejected
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Date: Wed, 8 Oct 2014 10:06:25 +0000
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Subject: Re: [MMUSIC] bundle-11: BUNDLE accpeted, but RTCP Mux rejected
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Christer,

From: Christer Holmberg [mailto:christer.holmberg@ericsson.com]
Sent: Dienstag, 7. Oktober 2014 20:35
To: Stach, Thomas; Harald Alvestrand; Cullen Jennings (fluffy)
Cc: mmusic
Subject: RE: bundle-11: BUNDLE accpeted, but RTCP Mux rejected

Hi Thomas,

>BUNDLE can be used separate from RFC5761 RTCP-Multiplexing.
>I can't find text in bundle-11 where the answerer would send its RTCP packets if it accepted BUNDLE, but rejected RTCP-muxing.
>I see two options:
>1. The answerer sends all RTCP packets to the shared RTP-port+1 of the negotiated shared address.
>2. The answerer sends the RTCP packets to separate ports based on the unique addresses in the m-lines of the offer?

Alternative 1) is correct. I guess we could add some text to clarify that.
[TS] Yes, please. The current text is not sufficiently clear.

>The offerer on the other hand will only receive a shared address. I assume it then has to send all its RTCP packets
>to the shared RTP-port+1 of the answerer.

Yes.

>Is my understanding correct or am I completely off-track?

Assuming my understanding is correct, your understanding is correct :)

>Supposed I'm correct, then independent from the response, I'm asking if there really is a use case for that.
>In case 1, one would have to demux the RTP streams and RTCP streams from two separate ports instead of a single port. How much implementation effort >is saved in that case?

I am not sure what you mean. Are you asking how much implementation effort is saved if you don't have to de-mux RTP and RTCP?
[TS] Yes.  I was questioning myself what benefit there is in not mandating RTCP-mux.
In the meantime I looked up again the discussion on "Q14" that led to having rtcp-mux optional. I agree with the outcome.
Thanks!

>In case 2 the RTCP handling at offerer and answerer is completely different. In addition, you still need "a lot" of RTCP ports and take advantage of only half >of the BUNDLE benefits.

Correct. But, case 2 is not applicable (unless the endpoints choose not to use BUNDLE to begin with, that is...).

Regards,

Christer