Re: [MMUSIC] BUNDLE and RTCP

Thomas Stach <thomass.stach@gmail.com> Mon, 19 October 2015 05:50 UTC

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To: Christer Holmberg <christer.holmberg@ericsson.com>, "mmusic@ietf.org" <mmusic@ietf.org>
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From: Thomas Stach <thomass.stach@gmail.com>
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Date: Mon, 19 Oct 2015 07:50:14 +0200
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Archived-At: <http://mailarchive.ietf.org/arch/msg/mmusic/HSMNoD_F9T2L6k3vxcDj_v4115U>
Subject: Re: [MMUSIC] BUNDLE and RTCP
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Christer,

of course there are many possibilities.
However it would be good to have some explicit signalling.
Without inventing new signalling elements, you could use the first RTP 
m-line that appears in the   a=group:BUNDLE attribute in the answer.

So if you have in the offer:

a=group:BUNDLE foo bar baz
m=data channel 10000
a=mid:foo
m=rtp 11111
a=mid:bar
a=rtcp: 15000
m=rtp 11222
a=mid:baz
a=rtcp: 20000

If you get back in the answer:

a=group:BUNDLE foo bar baz
...
then your RTCP port is 15000
If you get back a=group:BUNDLE foo baz bar then RTCP would go to 20000.

Although I haven't thought it through completely it too much this could 
also work reasonably well of the answerer accepts only a subset of the 
offered m-lines.

What do yo think?

Regards
Thomas


Am 18.10.2015 um 19:53 schrieb Christer Holmberg:
>
> Hi,
>
> Note that the issue exists even without bundle-only m- lines:
>
> m=data channel 10000
>
> m=rtp 11111
>
> a=rtcp: 15000
>
> m=rtp 11222
>
> a=rtcp: 20000
>
> Again, if the data channel m-  line is selected as the offerer BUNDLE 
> address, which port will be used for RTCP?
>
> Regards,
>
> Christer
>
> *From:*mmusic [mailto:mmusic-bounces@ietf.org] *On Behalf Of *Christer 
> Holmberg
> *Sent:* 18 October 2015 20:47
> *To:* mmusic@ietf.org
> *Subject:* [MMUSIC] BUNDLE and RTCP
>
> Hi,
>
> During the proto write-up process of BUNDLE, an issue came up.
>
> Assume the following BUNDLE offer, with one non-bundle-only data 
> channel m- line and one bundle-only RTP m- line:
>
> m=data channel 10000
>
> m=rtp 0
>
> a=bundle-only
>
> Now, if bundle is accepted, the RTP m- line will get port 10000, as 
> defined in BUNDLE. So far so good.
>
> Now, if bundle is accepted, the data channel m- line will be selected 
> as the offerer BUNDLE address, and RTP will use port 1000.
>
> So far so good.
>
> Next, assume we want to negotiate an explicit RTCP port for RTP. As 
> the non-bundle-only m- line is not RTP (and therefore cannot contain 
> an rtcp attribute), we have to add the actual RTCP port value to the 
> bundle-only m- line:
>
> m=data channel 10000
>
> m=rtp 0
>
> a=bundle-only
>
> a=rtcp: 20000
>
> So far so good.
>
> Now, assume we also have one non-bundle-only RTP m- line:
>
> m=data channel 10000
>
> m=rtp 11111
>
> a=rtcp: 15000
>
> m=rtp 0
>
> a=bundle-only
>
> a=rtcp: 20000
>
> Now, assume the data channel m- line is selected as the offerer BUNDLE 
> address. It means that port 10000 will also be used for RTP. But, 
> which port will be used for RTCP? 15000 or 20000?
>
> Regards,
>
> Christer
>
>
>
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