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

Randall Gellens <rg+ietf@randy.pensive.org> Sun, 07 January 2018 03:22 UTC

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Date: Sat, 6 Jan 2018 19:22:36 -0800
To: Eric Rescorla <ekr@rtfm.com>, "The IESG" <iesg@ietf.org>
From: Randall Gellens <rg+ietf@randy.pensive.org>
Cc: slim@ietf.org, draft-ietf-slim-negotiating-human-language@ietf.org, slim-chairs@ietf.org, bernard.aboba@gmail.com
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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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At 5:39 PM -0800 1/6/18, Eric Rescorla wrote:

>  Document: draft-ietf-slim-negotiating-human-language-17.txt
>
>  1. I'm not marking this first point DISCUSS, but I do think it's
>  important it be addressed and I trust the AD will ensure that it is.
>  This document is ambiguous about the contents of the answer
>  attribute. Specifically, it says:
>
>     In an answer, 'hlang-send' is the language the answerer will send if
>     using the media for language (which in most cases is one of the
>     languages in the offer's 'hlang-recv'), and 'hlang-recv' is the
>     language the answerer expects to receive if using the media for
>     language (which in most cases is one of the languages in the offer's
>     'hlang-send').
>
>  However, the next paragraph permits >1 tag, as does the ABNF in S 6.1.
>
>     Each value MUST be a list of one or more language tags per BCP 47
>     [RFC5646], separated by white space.  BCP 47 describes mechanisms for
>     matching language tags.  Note that [RFC5646] Section 4.1 advises to
>     "tag content wisely" and not include unnecessary subtags.
>
>  So, how am I supposed to interpret an answer with >1 tag? Is this
>  forbidden? I can imagine a number of semantics, but it's important
>  it be clear in the document.

Thank you for catching this.  I think the first paragraph is correct 
and the second paragraph and ABNF are in error, they were copied from 
the offer and not fixed.  The intent is that a single language per 
direction be arrived it per media stream.


>  2. The negotiation structure here does not match that which is
>  conventionally used with SDP, where each side indicates the formats it
>  is prepared to receive and the other side can send any of them. Why
>  did you use this structure? One reason you might is that you expect
>  the answer to resolve which language is in use, however because SIP
>  supports early media (i.e., media which is delivered prior to the
>  answer.)

In light of my reply to (1), do you still feel that the negotiation 
structure doesn't match usual offer/answer behavior?

-- 
Randall Gellens
Opinions are personal;    facts are suspect;    I speak for myself only
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