Re: [MMUSIC] QUERY: info about a=cat, a=keywds, a=tool

Colin Perkins <csp@csperkins.org> Wed, 06 August 2014 09:48 UTC

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From: Colin Perkins <csp@csperkins.org>
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Date: Wed, 6 Aug 2014 10:48:05 +0100
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Subject: Re: [MMUSIC] QUERY: info about a=cat, a=keywds, a=tool
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Paul,

I think these come from the Mbone tools (Van Jacobson’s sd and Mark Handley’s sdr), which used the combination of SDP and the Session Announcement Protocol (SAP) for multicast session directories, TV guide-style. 

The a=tool: attribute was introduced in draft-ietf-mmusic-sdp-03; the others are both in http://tools.ietf.org/id/draft-ietf-mmusic-sdp-01.txt (draft-ietf-mmusic-sdp-00 is missing from the archive). Mark Handley’s slides from the MMUSIC meeting at IETF 33 have some details ftp://ftp.ietf.org/ietf-online-proceedings/95jul/area.and.wg.reports/tsv/mmusic/mmusic.handley.slides.ps

Colin




On 5 Aug 2014, at 16:48, Paul Kyzivat <pkyzivat@alum.mit.edu> wrote:
> I volunteered to draft ABNF syntax for the attributes defined in RFC4566 (SDP).
> 
> There are some that I have very little information about:
> 
>   a=cat:<category>
>   a=keywds:<keywords>
>   a=tool:<name and version of tool>
> 
> They have all been in SDP since RFC2327 in 1998. And I don't think I have ever seen any of them used. I did a google search over ietf.org looking for usages without luck. And they are all very vague about their syntax.
> 
> The safe answer is to just define the value syntax for each of then as <byte-string>. But at least for a=cat the value (category) is specified as "dot-separated hierarchical category", so it seems reasonable that the syntax ought to involve dots in some way.
> 
> Perhaps these should all be deprecated.
> 
> Is there anybody still here who remembers when these were defined, and what the expectations were about the syntax?
> 
> 	Thanks,
> 	Paul
> 
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-- 
Colin Perkins
http://csperkins.org/