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

Paul Kyzivat <pkyzivat@alum.mit.edu> Fri, 12 February 2016 17:39 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: Fri, 12 Feb 2016 12:39:50 -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 4:13 PM, Flemming Andreasen wrote:

>>> 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 ?

I don't see how any of the currently defined precondition types 
(connectivity, qos, security) make sense at the data channel level. But 
all of them could make sense when applied to the overall SCTP 
association over which the channels run.

I suppose *in theory* some hypothetical new precondition type might 
apply to a channel, but we have nothing suggesting that.

I will grant that we could just take the position that any attribute can 
be used anywhere, and that the general "ignore if you don't understand" 
rule will prevent problems.

My basic concern is that when an attribute is used in some context, that 
the semantics for such use are well defined, so that an independent 
observer can determine whether the usage is proper.

	Thanks,
	Paul