Re: [rtcweb] BUNDLE with implicit rtcp-mux

Justin Uberti <juberti@google.com> Thu, 13 March 2014 16:17 UTC

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From: Justin Uberti <juberti@google.com>
Date: Thu, 13 Mar 2014 09:16:57 -0700
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To: Christer Holmberg <christer.holmberg@ericsson.com>
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Subject: Re: [rtcweb] BUNDLE with implicit rtcp-mux
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On Thu, Mar 13, 2014 at 5:52 AM, Christer Holmberg <
christer.holmberg@ericsson.com> wrote:

> Hi Justin,
>
> > I think rtcp-mux has to be a MUST use when BUNDLE is used between the
> two endpoints. (If the endpoint doesn't support
> > BUNDLE, rtcp-mux is not required.)
> >
> > Otherwise, you get into weird edge cases, such as where you have a data
> channel (no RTCP component), and then want
> > to add audio (with RTP and RTCP components). You could bundle the audio
> RTP over the existing data channel transport,
> > but it's not clear what you should do with the RTCP component. Mandating
> rtcp-mux avoids this issue completely.
>
> According to section 4 in RFC 5761, if you multiplex RTP and RTCP on the
> same port, you need to assign dedicated PT values to the RTCP packets,
> which means that at least PT values 64-95 cannot be used for RTP.
>
> As you have been one of those talking about the risk of running out of PT
> values, I just want to make sure you have taken this into consideration :)
>
>
Yes. The upside of rtcp-mux far outweighs this minor limitation.