Re: [MMUSIC] WGLC for draft-ietf-mmusic-data-channel-sdpneg

Paul Kyzivat <pkyzivat@alum.mit.edu> Mon, 08 February 2016 17:09 UTC

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To: Flemming Andreasen <fandreas@cisco.com>, mmusic@ietf.org
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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Date: Mon, 8 Feb 2016 12:09:09 -0500
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Cc: draft-ietf-mmusic-data-channel-sdpneg@ietf.org
Subject: Re: [MMUSIC] WGLC for draft-ietf-mmusic-data-channel-sdpneg
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On 2/8/16 11:09 AM, Flemming Andreasen wrote:
>
>
> On 2/6/16 1:44 PM, Paul Kyzivat wrote:
>> On 2/4/16 10:43 PM, Christian Groves wrote:
>>> Isn't this the approach we're taking today?
>>> draft-ietf-mmusic-data-channel-sdpneg has general text and specific
>>> drafts are used to describe protocols that use the mechanism (i.e.
>>> draft-ietf-mmusic-msrp-usage-data-channel &
>>> draft-ietf-clue-datachannel).
>>
>> It remains to be seen if that will be enough. E.g., there currently
>> aren't any iana considerations in
>> draft-ietf-mmusic-msrp-usage-data-channel.
>>
>> Suppose I encounter some sdp that uses msrp over a data channel, but
>> that usage is unknown to me. How do I find the spec (the reference to
>> draft-ietf-mmusic-msrp-usage-data-channel) that defines that usage?
>>
>> I would like to think that the iana registries will allow me to trace
>> back to the relevant specs.
>>
> No disagreement on that part, however having taken another look at both
> sdpneg and the msrp-usage documents, I still don't agree with your
> original request for all (existing and new) attributes to specify how
> they may or may not be used with the dcsa attribute defined by sdpneg.
>
> As Christian noted, the sub-protocol specifics are defined in individual
> documents (like msrp-usage), which calls your the parameters that are at
> least needed to be supported for that usage. Taking MSRP as an example,
> why isn't that enough, and how do you see the resulting set of
> attributes that may or may not be used with MSRP differ between use in a
> data-channel (and hence encapsulated in dcsa) or as a regular media
> stream ?

Based on this discussion, I conclude that it should be sufficient for 
this draft to say that before an attribute can be used with dcsa, such 
usage must be defined somewhere. This could be either:
- as part of the definition of the attribute, OR
- as part of the definition of the protocol referenced on the m-line.

	Thanks,
	Paul

> Also, it would be good to hear from more people on this, including the
> document authors.
>
> Thanks
>
> -- Flemming
>
>
>>     Thanks,
>>     Paul
>>
>>> Regards, Christian
>>>
>>> On 4/02/2016 3:58 PM, Paul Kyzivat wrote:
>>>> On 2/3/16 5:42 PM, Flemming Andreasen wrote:
>>>>
>>>>> I'm not concerned about the IANA part. I agree that *if* we need to
>>>>> expliclty specify attribute interactions for "dcsa", then it should be
>>>>> part of the IANA registry. What I am not agreeing with at this
>>>>> point is
>>>>> that there is indeed a need to explicitly speficy these
>>>>> interactions as
>>>>> opposed to relying on a more general algorithmic approach (plus the
>>>>> offerer being responsible for generating a valid offer if he wants to
>>>>> establish a data channel).
>>>>
>>>> Well, an obvious one is that the protocol(s) the attribute pertains to
>>>> need to be defined to work over data channels.
>>>>
>>>>     Thanks,
>>>>     Paul
>>>>
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>>>
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>>
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>
>