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

Flemming Andreasen <fandreas@cisco.com> Thu, 11 February 2016 21:13 UTC

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To: Paul Kyzivat <pkyzivat@alum.mit.edu>, 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: Flemming Andreasen <fandreas@cisco.com>
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Date: Thu, 11 Feb 2016 16:13:35 -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 4:00 PM, Paul Kyzivat wrote:
> 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?
>
How about preconditions ?

-- Flemming
>     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
>>>>>>>
>>>>>>
>>>>>> _______________________________________________
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>>>>>> mmusic@ietf.org
>>>>>> https://www.ietf.org/mailman/listinfo/mmusic
>>>>>>
>>>>>
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>
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