Re: [MMUSIC] BUNDLE and RTCP

[Thomas Stach <[e-mail]>]

Christer,

Am 19.10.2015 um 08:41 schrieb Christer Holmberg:
>
> Hi Thomas,
>
> >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?
>
> I am sure we COULD do something like that. I also have some ideas, but 
> I think they are all too hacky and/or complex for what we would gain.
>
> HOWEVER, we could make it SIMPLE and either:
>
> 1)*Mandate usage of rtcp-mux with BUNDLE*. I.e. if BUNDLE is 
> negotiated, rtcp-mux MUST be used.
>
> This was already suggested in the past, but Paul(?) said we should not 
> make such restriction without a good reason. I think the current issue 
> is a good reason :)
>
> m=data channel 10000
>
> m=rtp 11111
>
> a=rtcp-mux
>
> m=rtp 11222
>
> a=rtcp-mux
>
> 2)*Mandate usage of either rtcp-mux OR the default “+1” port with 
> BUNDLE*. I.e. if BUNDLE is negotiated, rtcp-mux or “+1” MUST be used. 
> The selection is based on whether the rtcp-mux attribute was included 
> in the offer/answer or not.
>
> m=data channel 10000             // rtcp-mux
>
> m=rtp 11111
>
> a=rtcp-mux
>
> m=rtp 11222
>
> a=rtcp-mux
>
> m=data channel 10000             // “+1”
>
> m=rtp 11111
>
> m=rtp 11222
>
> The solutions above would not allow explicit negotiation of an RTCP 
> port when BUNDLE is used, but maybe we could live with that?
>
Well, I could live with both of your suggestions, but I thought you 
wanted a solution that can also negotiate which a=rtcp attribute to use.
If nobody really needs something like that , I would prefer 1) as it 
removes the needs for several implementation option that would only be 
needed to cover full backwards compatibility but would hardly be used.
>
> Now, if we can agree on a way forward before Yokohama, you won’t have 
> to sit listening to me talking about BUNDLE at the meeting :)
>
Well, I wouldn't be sitting there anyhow but understand that your 
motivation to speak there about BUNDLE again is probably limited.
Regards
Thomas
>
> Regards,
>
> Christer
>
> 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:[e-mail]] *On Behalf Of
>     *Christer Holmberg
>     *Sent:* 18 October 2015 20:47
>     *To:* [e-mail] <mailto:[e-mail]>
>     *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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