Re: [Slim] Eric Rescorla's No Objection on draft-ietf-slim-negotiating-human-language-19: (with COMMENT)

Eric Rescorla <ekr@rtfm.com> Sun, 07 January 2018 14:36 UTC

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From: Eric Rescorla <ekr@rtfm.com>
Date: Sun, 7 Jan 2018 06:36:12 -0800
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To: Bernard Aboba <bernard.aboba@gmail.com>
Cc: Bernard Aboba <bernard_aboba@hotmail.com>, "slim@ietf.org" <slim@ietf.org>
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Subject: Re: [Slim] Eric Rescorla's No Objection on draft-ietf-slim-negotiating-human-language-19: (with COMMENT)
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On Sat, Jan 6, 2018 at 7:31 PM, Bernard Aboba <bernard.aboba@gmail.com>
wrote:

> On Jan 6, 2018, at 6:55 PM, Eric Rescorla <ekr@rtfm.com> wrote:
>
> For disabled users, the capabilities may not be symmetric.
>
>
> But this is true for ordinary SDP as well. I might be able to receive
> H.264 but not send it.
>
>
> [BA] Thanks. The draft should explain the reasoning. IMHO the argument
> goes sonething like this:
>
> A pure recv/recv negotiation will not necessarily disclose beforehand what
> special services are needed for the call - services (e.g. ASL
> interpretation or RTT handling) that could take time to acquire.
>
> Since the actual video media sent is not labelled as ASL even if the
> answerer has ASL interpreters it can pull in and therefore advertises in
> SDP ASL reception capability in video, a recv/recv negotiation doesn’t tell
> the Answerer that the Offerer will need them, so the Answerer may need to
> (frantically) arrange for ASL interpretation after initial receipt of
> media. In an emergency, that can chew up valuable time.
>

Thanks. I think it would be helpful to put this logic in the draft.

That said, as I noted in my review, it is still possible to get some media
(early media) prior to receiving the answer, so this isn't a complete
solution.

-Ekr