Reviewer: Dale Worley Review result: Ready with Nits I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair. Please treat these comments just like any other last call comments. For more information, please see the FAQ at <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. Document: draft-ietf-slim-negotiating-human-language-06 Reviewer: Dale R. Worley Review Date: 2017-02-17 IETF LC End Date: 2017-02-20 IESG Telechat date: [unknown] Summary: This draft is basically ready for publication, but has nits that should be fixed before publication. * Technical comments A. Call failure If a call fails due to no available language match, in what way(s) does it fail? Section 5.3 says If such an offer is received, the receiver MAY reject the media, ignore the language specified, or attempt to interpret the intent But I suspect it's also allowed for the UAS to fail the call at the SIP level. Whether or not that is allowed (or at least envisioned) should be described. And what response code(s)/warn-code(s) should be used for that? B. Audio/Video coordination 5.2. New 'humintlang-send' and 'humintlang-recv' attributes Note that while signed language tags are used with a video stream to indicate sign language, a spoken language tag for a video stream in parallel with an audio stream with the same spoken language tag indicates a request for a supplemental video stream to see the speaker. And there's a similar paragraph in 5.4: > A spoken language tag for a video stream in conjunction with an audio > stream with the same language might indicate a request for > supplemental video to see the speaker. I think this mechanism needs to be described more exactly, and in particular, it should not depend on the UA understanding which language tags are spoken language tags. It seems to me that a workable rule is that there is an audio stream and a video stream and they specify exactly the same language tag in their respective humintlang attributes. In that case, it is a request for a spoken language with simultaneous video of the speaker, and those requests should be considered satisfied only if both streams can be established. * The following three items are adjustments to the design which I'd like to know have been considered. C. "humintlang" seems long to me Given the excessive length of SDP in practice, it seems to me that a shorter attribute name would be desirable. E.g., "humlang" as was used in some previous versions. Or is there a coordinated usage with other names in the "hum*lang" pattern? D. Use the Accept-Language syntax It seems to me that it would better to use the Accept-Language syntax for the attribute values. This allows (1) specifiying the quality of language experience, allowing clear description of bilingualism, (2) a unified method of specifying whether or not arbitrary languages are acceptable, and (3) abbreviating SDP descriptions. In a way, the fact that the current proposal seems to require (but does not directly specify) the coordinated absence/presence of an asterisk on all of the repetitions of humintlang-send or humintlang-recv is a warning that the syntax doesn't represent the semantics as well as it might. E. Have an attribute to abbreviate the bidirectionally-symmetric case Note that all examples are bidirectionally symmetric, and the text says that requests and responses SHOULD be bidirectionally symmetric. So it would be a very useful abbreviation to define "humintlang=<value>" to be equivalent to the combination of "humintlang-send=<value>" and "humintlang-recv=<value>". Combining proposals C, D, and E, the examples become m=audio 49170 RTP/AVP 0 a=humlang:en m=video 51372 RTP/AVP 31 32 a=humlang:ase,*;q=0.1 m=audio 49250 RTP/AVP 20 a=humlang:es,eu;q=0.9,en;q=0.8,*;q=0.1 m=text 45020 RTP/AVP 103 104 a=humlang:gr which requires about half as many characters as they have now. * Editorial comments and nits Abstract This document describes the need and a solution using new SDP stream attributes. I don't think the term "stream attribute" is used in RFC 4566. Instead, it uses "media attribute". 1. Introduction caller and callee know each other or there is contextual or out of band information from which the language(s) and media modalities can I think this context, it's preferred to hyphenate "out-of-band" to make it clearly be an adjective. This approach has a number of benefits, including that it is generic (applies to all interactive communications negotiated using SDP) and not limited to emergency calls. I think s/and not limited to/and is not limited to/ reads more smoothly. But it is clearly useful in many other cases. For example, someone calling a company call center or a Public Safety Answering Point (PSAP) should be able to indicate if one or more specific signed, written, and/or spoken languages are preferred, the callee should be able to indicate its capabilities in this area, and the call proceed using in-common language(s) and media forms. I think s/preferred, the callee/preferred; the callee/ because the sentence is the concatenation of two sentences. Perhaps s/in-common/shared/. Including the user's human (natural) language preferences in the session establishment negotiation is independent of the use of a relay service and is transparent to a voice service provider. I think it's even broader than "transparent to a voice service provider" -- it's transparent to any serivice provider, assuming that the media are language-neutral. In the case of a call to e.g., an airline, the call could be automatically handled by a Spanish-speaking agent. I think s/handled by/routed to/ is the usual usage. 3. Desired Semantics The desired solution is a media attribute (preferably per direction) that may be used within an offer to indicate the preferred language of each (direction of a) media stream, and within an answer to indicate the accepted language. In this one instance, I think you want to use "language(s)" to drive home that that multiple languages can be specified: "within an offer to indicate the preferred language(s)". (Negotiating multiple simultaneous languages within a media stream is out of scope, as the complexity of doing so outweighs the usefulness.) You might want to say instead "(Negotiating multiple simultaneous languages within a media stream is out of scope for this document.)" to ensure that nobody decides to argue whether "the complexity of doing so outweighs the usefulness". 4. The existing 'lang' attribute RFC 4566 [RFC4566] specifies an attribute 'lang' which appears similar to what is needed here, but is not sufficiently detailed for use here. "for use here" isn't quite right. Maybe "is not sufficiently specific or flexible to satisfy the requirements". In addition, it is not mentioned in [RFC3264] "it" is somewhat ambiguous here, perhaps change to "the 'lang' attribute". 5. Proposed Solution Perhaps /Proposed Solution/Solution/, since once this draft is approved, it becomes the solution. 5.2. New 'humintlang-send' and 'humintlang-recv' attributes a=humintlang-send:<language tag> a=humintlang-recv:<language tag> This is presented as the generic form of the attributes, but there is no indication of the posible asterisk. The values constitute a list of languages in preference order (first is most preferred). "The values" isn't very clear, because the values are in successive attributes. You want to say something like "The sequence of values in the occurrences of one of these attributes constitutes ...". However, see the technical comments above. When placing an emergency call, and in any other case where the language cannot be assumed from context, each media stream in an offer primarily intended for human language communication SHOULD specify both (or in some cases, one of) the 'humintlang-send' and 'humintlang-recv' attributes. Probably s/assumed/inferred/. Could you be more accurate by s/or in some cases/or for unidirectional streams/? 5.3. Advisory vs Required The mechanism for indicating this preference is that, in an offer, if the last character of any of the 'humintlang-recv' or 'humintlang- send' values is an asterisk, this indicates a request to not fail the call (similar to SIP Accept-Language syntax). Either way, the called party MAY ignore this, e.g., for the emergency services use case, a PSAP will likely not fail the call. The construction of this paragraph isn't quite complete. It says that if an asterisk is present, a request shouldn't fail, but it doesn't say that if no asterisk is present, a request should fail if there is no language match. And it's the latter condition that makes the second sentence meaningful. So I think you want to insert between the two sentences one regarding the absence of an asterisk. 5.5. Examples Given that the combined audio/video mechanism is the only irregularity in this system, there ought to be an example of it. E.g., An example of a supplemental video stream with a spoken language audio stream: m=video 51372 RTP/AVP 31 32 a=humintlang-send:en a=humintlang-recv:en m=audio 49250 RTP/AVP 20 a=humintlang-send:en a=humintlang-recv:en 6. IANA Considerations humintlang-value = Language-Tag [ asterisk ] ; Language-Tag defined in RFC 5646 asterisk = "*" s/Language-Tag defined in RFC 5646/Language-Tag as defined in RFC 5646/ But perhaps also s/RFC 5646/BCP 47/, which ensures that "humintlang" tracks the current version of language tags. Appendix A. Historic Alternative Proposal: Caller-prefs This results in a more fragile solution since the media modality and language would be negotiated using SIP, and then the specific media formats (which inherently include the modality) would be negotiated at a different level (typically SDP, especially in the emergency calling cases), making it easier to have mismatches (such as where the media modality negotiated in SIP don't match what was negotiated using SDP). "the media modality and language would be negotiated using SIP" isn't quite the right way to say it because SIP isn't explicitly negotiating the modality. Better would be ... the language (and by implication the media modality) would be negotiated using SIP, and then the specific media (which inherently include the modalities and formats) would be negotiated at a different level ... [END]