Re: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question

Christer Holmberg <christer.holmberg@ericsson.com> Thu, 02 October 2014 12:16 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>, "mmusic@ietf.org" <mmusic@ietf.org>
Thread-Topic: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question
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Date: Thu, 2 Oct 2014 12:16:28 +0000
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Subject: Re: [MMUSIC] draft-ietf-mmusic-sctp-sdp-07 SCTP SDP syntax question
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Hi,

>>> The association-usage is describing how the association as a whole, 
>>> including all of the streams, is used/managed.
>>>
>>> It doesn't provide a means to separately describe how individual 
>>> streams within it are to be used. If that is to be done in SDP then 
>>>> something like draft-ejzak... would be required.
>>
>> [CNG] My comments on this are in the context of the note in cl.10 of 
>> the
>> draft: "[Note] TBD whether a new registry is necessary to register the 
>> different possible "association-usage" values."
>
> Well, the alternatives to establishing a new registry are:
>
> - use an existing registry
>
>- define all the values directly in the draft.
>   (This will then require a revision to define new ones.)

I think we should have a registry (I don't care whether it's new, or an existing one).

> I don't see how we could use an existing one, since the semantics of what are being defined are entirely 
> new. (The websocket protocol registry isn't right for this. It defines a *protocols* that run over a websocket, or 
> at least something similar in nature to a websocket. What we are defining here isn't a protocol in the same sense - it is a
> *convention* for how to use an SCTP association including the many streams it contains. Each of those streams may have its 
> own protocol.)

I agree with that.

Then, IF someone e.g. would like to run RTP over SCTP, I guess they would need a new m= line protocol value. " DTLS/SCTP/RTP/AVP", or something like that...

> We could live without any registry *if* we think there is very low likelihood of needing to define new values. But I think it is already clear that is a bad assumption.

Let's also keep in mind that, while we have been discussing mostly "DTLS/SCTP", the draft also defines "SCTP" and "SCTP/DTLS". Hopefully we could use a single registry for all of them...

Regards,

Christer