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Re: [MMUSIC] 4566bis-36: Ignoring/rejecting session description that contains unknown letter

Paul Kyzivat <pkyzivat@alum.mit.edu> Fri, 26 July 2019 17:02 UTC

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From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Date: Fri, 26 Jul 2019 13:02:35 -0400
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Subject: Re: [MMUSIC] 4566bis-36: Ignoring/rejecting session description that contains unknown letter
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On 7/24/19 5:49 AM, Christer Holmberg wrote:
> Hi,
> 
> Due to my involvement in a large number of other drafts, I haven’t been 
> able to follow the 4566bis work lately.
> 
> I do have a question.
> 
> The text says:
> 
>     “The set of type letters is deliberately small and not intended to be
> 
>     extensible -- an SDP parser MUST completely ignore or reject any
> 
>     session description that contains a type letter that it does not
> 
> understand.”
> 
> Since the syntax does not allow new letters to begin with, why can’t an 
> SDP parser simply discard an unknown letter if received? Why does the 
> parser have to ignore/reject the whole session description?

This has always been part of the description of SDP. It would be odd to 
change it now. AFAIK there has never been another letter added to the 
syntax. (Related to the point that the version has never been changed, 
and there is no mechanism for changing it in a backward compatible way.)

	Thanks,
	Paul

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