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

Paul Kyzivat <pkyzivat@alum.mit.edu> Thu, 11 February 2016 21:00 UTC

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To: Flemming Andreasen <fandreas@cisco.com>, mmusic@ietf.org, "DRAGE, Keith (Keith)" <keith.drage@alcatel-lucent.com>, "bradler >> Juergen Stoetzer-Bradler" <Juergen.Stoetzer-Bradler@alcatel-lucent.com>
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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Date: Thu, 11 Feb 2016 16:00:19 -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 2/11/16 3:52 PM, Flemming Andreasen wrote:
>
>
> On 2/8/16 12:09 PM, Paul Kyzivat wrote:
>> 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.
>>
> We are getting closer, but it's still not obvious to me that you cannot
> use an attribute with dcsa if it has not been explicitly defined for the
> attribute in question.

Can you give me an example?

	Thanks,
	Paul

> Clearly, there are attributes that wouldn't make
> sense over data channels, just like there are attributes that don't make
> sense over particular media descriptions.
>
> Again, I'd like to hear from more people on this, including the authors.
>
> Thanks
>
> -- Flemming
>
>
>
>>     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
>>>>>>
>>>>>> _______________________________________________
>>>>>> mmusic mailing list
>>>>>> mmusic@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> mmusic mailing list
>>>>> mmusic@ietf.org
>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
>>
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>
>