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

[Randall Gellens <[e-mail]>]

At 9:57 AM -0800 1/8/18, Randall Gellens wrote:

>  At 9:48 AM -0800 1/8/18, Eric Rescorla wrote:
>
>>   On Mon, Jan 8, 2018 at 9:41 AM, Randall Gellens 
>> <<mailto:[e-mail]>[e-mail]> 
>> wrote:
>>
>>   At 5:56 PM -0800 1/7/18, Eric Rescorla wrote:
>>
>>    On Sun, Jan 7, 2018 at 5:22 PM, Randall Gellens 
>> <<mailto:<mailto:[e-mail]>[e-mail]><mailto:[e-mail]>[e-mail]> 
>> wrote:
>>
>>    At 6:36 AM -0800 1/7/18, Eric Rescorla wrote:
>>
>>     On Sat, Jan 6, 2018 at 7:31 PM, Bernard Aboba 
>> <<mailto:<mailto:<mailto:[e-mail]>[e-mail]><mailto:[e-mail]>[e-mail]><mailto:<mailto:[e-mail]>[e-mail]><mailto:[e-mail]>[e-mail]> 
>> wrote:
>>
>>     On Jan 6, 2018, at 6:55 PM, Eric Rescorla 
>> <<mailto:<mailto:<mailto:[e-mail]>[e-mail]><mailto:[e-mail]>[e-mail]><mailto:<mailto:[e-mail]>[e-mail]><mailto:[e-mail]>[e-mail]> 
>> 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.
>>
>>
>>    I am not clear on what logic we want to add to the draft, or 
>> what about the draft this logic is explaining.
>>
>>
>>    It would be helpful to explain in the draft why you have 
>> deviated from the otherwise near-universal SDP negotiation pattern 
>> of each side advertising what it accepts.
>>
>>
>>   I'm not clear on what you're referring to.  Are you talking about 
>> early offer versus late offer?  To my understanding, the draft 
>> follows a typical offer/answer model: the caller lists the media 
>> and languages it supports, and the callee answers with the media 
>> and languages it supports.
>>
>>
>>   That's not what this draft does. The typical SDP pattern is what 
>> you say here: that the offerer (which might or might not be the 
>> caller) lists what it supports and the answerer lists what it 
>> supports.
>>   So, for instance, the offerer might list "VP8, H.264" and the 
>> answerer might respond with "VP8, H.264", at which point either 
>> side could use either codec (or intermix them). What this draft 
>> does is have the offerer list what it supports and the answerer 
>> picks exactly one. I understood from the previous emails in the 
>> thread that the reason for this design was so that each side then 
>> knew exactly what languages would be used. However, as noted 
>> upthread, this draft does not provide this function if early media 
>> is used, because the media is delivered to the offerer prior to 
>> receiving the answer, so the offerer is in the same position as it 
>> would be with the typical negotiation model.
>
>  Thanks, I think I understand your concern now.  You'd like the 
> draft to explain why the answer contains one language per media 
> stream, which is partly for provide knowledge so both ends know 
> what has been negotiated, but also because supporting languages 
> and/or modalities may require taking extra steps, such as having a 
> call handled by an agent who speaks a requested language and/or can 
> use a requested modality, or bridging external translation or relay 
> resources into the call, etc.  The answerer indicates which 
> additional steps it is committing to.  These steps may or may not 
> be in place in time for early media.  I can add text explaining 
> this to the Introduction.


The third paragraph below is the additional text added to the 
Introduction (the first two paragraphs are unchanged):

    By treating language as another SDP attribute that is negotiated
    along with other aspects of a media stream, it becomes possible to
    accommodate a range of users' needs and called party facilities.  For
    example, some users may be able to speak several languages, but have
    a preference.  Some called parties may support some of those
    languages internally but require the use of a translation service for
    others, or may have a limited number of call takers able to use
    certain languages.  Another example would be a user who is able to
    speak but is deaf or hard-of-hearing and and desires a voice stream
    to send spoken language plus a text stream to receive written
    language.  Making language a media attribute allows the standard
    session negotiation mechanism to handle this by providing the
    information and mechanism for the endpoints to make appropriate
    decisions.

    The term "negotiation" is used here rather than "indication" because
    human language (spoken/written/signed) can be negotiated in the same
    manner as media (audio/text/video) and codecs.  For example, if we
    think of a user calling an airline reservation center, the user may
    have a set of languages he or she speaks, with perhaps preferences
    for one or a few, while the airline reservation center will support a
    fixed set of languages.  Negotiation should select the user's most
    preferred language that is supported by the call center.  Both sides
    should be aware of which language was negotiated.  This is
    conceptually similar to the way other aspects of each media stream
    are negotiated using SDP (e.g., media type and codecs).

    In the offer/answer model used here, the offer contains a set of
    languages per media that the caller is capable of using, and the
    answer contains one language per media that the answerer will
    support.  Supporting languages and/or modalities can require taking
    extra steps, such as having a call handled by an agent who speaks a
    requested language and/or with the ability to use a requested
    modality, or bridging external translation or relay resources into
    the call, etc.  The answerer indicates in the answer which additional
    steps it is committing to.  This model also provides knowledge so
    both ends know what has been negotiated.  Note that additional steps
    required to support the indicated languages or modalities may or may
    not be in place in time for any early media.

>
>>
>>
>>     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.
>>
>>
>>    The draft provides a useful mechanism that will be helpful.  As 
>> an example of the fact that others find it useful, NENA has 
>> included it in it's next-generation emergency call architecture 
>> standards. The draft does not try to solve all problems related to 
>> human language in real-time calling.
>>
>>
>>    I don't think I claimed it wasn't useful.
>>
>>    The rationale provided for this design is that you wish to have 
>> the answerer notify the offerer of which language it would be 
>> providing. The point I am making is that there is at least one 
>> important case where this design does not provide that, which 
>> seems like it's relevant to the design question.
>>
>>
>>   I think I'm still not understanding your concern.  Even without 
>> providing a mechanism for the caller to know the languages used 
>> with any early media, the draft is still meeting a need.
>>
>>
>>   I'm honestly not sure what you're responding to here. I'm not 
>> saying that the draft doesn't meet a need.
>>
>>   -Ekr
>>
>>
>>
>>
>>   --
>>   Randall Gellens
>>   Opinions are personal;    facts are suspect;    I speak for myself only
>>   -------------- Randomly selected tag: ---------------
>>   Imagination is more important than facts. --Albert Einstein
>>
>>
>>
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>
>
>  --
>  Randall Gellens
>  Opinions are personal;    facts are suspect;    I speak for myself only
>  -------------- Randomly selected tag: ---------------
>  Algol was a great improvement on most of its successors.
>                                           --C.A.R Hoare
>
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-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
-------------- Randomly selected tag: ---------------
If we do not change our direction we are likely to end up where we are
headed.