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Re: [AVTCORE] Need feedback on RFC5285bis (RTP header extensions) comments

Paul Kyzivat <pkyzivat@alum.mit.edu> Wed, 01 February 2017 18:48 UTC

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To: Roni Even <roni.even@huawei.com>, IETF AVTCore WG <avt@ietf.org>
References: <6E58094ECC8D8344914996DAD28F1CCD770167@DGGEMM506-MBX.china.huawei.com>
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Date: Wed, 01 Feb 2017 13:48:04 -0500
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Cc: David Singer <singer@apple.com>
Subject: Re: [AVTCORE] Need feedback on RFC5285bis (RTP header extensions) comments
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On 2/1/17 5:42 AM, Roni Even wrote:

> 4.       Is it valid to use IDs in the (unusable) range in answers? (I
> guess that would give the offerer info that it could use in a future
> offer.). I am not sure what was meant here. Is it an answer to an offer
> with an ID in the valid range? Or is it about keeping an alternative
> from the offer with the unusable space and not remove it? I assume that
> the answer cannot add extensions to the ones in the offer, will need a
> new offer for that.

Clarifying what I meant:

My first question is: is it valid an extmap attribute with an ID in the 
(unusable) range appear in an SDP answer?

If the answer to that is Yes, then a followon question is: what does 
that mean?

It occurred to me that it might be used by the answerer to indicate to 
the offerer some extensions that it is willing to use that were not 
mentioned in the offer.

I ask this mostly for completeness - the spec is silent on the matter.

	Thanks,
	Paul

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