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

Paul Kyzivat <> Sun, 07 January 2018 17:53 UTC

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Date: Sun, 07 Jan 2018 12:53:25 -0500
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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 1/7/18 12:02 AM, Randall Gellens (IETF) wrote:
> It hasn't been my understanding that language would be sprung on users; 
> if video is requested in an offer to carry ASL, that would be in the 
> offer, and if the answerer can support ASL, the answer includes video 
> with ASL. In North America, callers needing sign language interpretation 
> or text translation usually initiate calls via the interpreter/relay 
> service, but this might not be true elsewhere.

This is a mechanism that has evolved as the path of least resistance and 
based on technology available at the time. But it is sub-optimal. To 
avoid recruiting an unneeded ASL interpreter requires knowing a priori 
that a callee supports ASL natively. Future technology will make it 
easier to discover the need for translation and recruit it dynamically. 
Hence the mechanism should not a priori knowledge of the need.


> In North America, PSAPs 
> have the ability to handle text calls (legacy PSAPs support TTY; 
> next-gen PSAPs support RTT). Calls needing language translation might 
> internally be handled by staff who speak the language or an external 
> language translation service might be bridged in, (e.g., an emergency 
> call routed to a PSAP in San Diego might have call takers who speak 
> Spanish but might need a third-party translator for French, the opposite 
> for a PSAP in Montreal).
> Sent from my iPad
> On Jan 6, 2018, at 7:31 PM, Bernard Aboba < 
> <>> wrote:
>> On Jan 6, 2018, at 6:55 PM, Eric Rescorla < 
>> <>> 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.
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