idnits 2.17.1 draft-ietf-slim-negotiating-human-language-21.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to lack the recommended RFC 2119 boilerplate, even if it appears to use RFC 2119 keywords -- however, there's a paragraph with a matching beginning. Boilerplate error? (The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (January 9, 2018) is 2298 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 4566 (Obsoleted by RFC 8866) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Gellens 3 Internet-Draft Core Technology Consulting 4 Intended status: Standards Track January 9, 2018 5 Expires: July 13, 2018 7 Negotiating Human Language in Real-Time Communications 8 draft-ietf-slim-negotiating-human-language-21 10 Abstract 12 Users have various human (natural) language needs, abilities, and 13 preferences regarding spoken, written, and signed languages. This 14 document adds new SDP media-level attributes so that when 15 establishing interactive communication sessions ("calls"), it is 16 possible to negotiate (communicate and match) the caller's language 17 and media needs with the capabilities of the called party. This is 18 especially important with emergency calls, where a call can be 19 handled by a call taker capable of communicating with the user, or a 20 translator or relay operator can be bridged into the call during 21 setup, but this applies to non-emergency calls as well (as an 22 example, when calling a company call center). 24 This document describes the need and a solution using new Session 25 Description Protocol (SDP) media attributes. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on July 13, 2018. 44 Copyright Notice 46 Copyright (c) 2018 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 1.1. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 64 3. Desired Semantics . . . . . . . . . . . . . . . . . . . . . . 5 65 4. The existing 'lang' attribute . . . . . . . . . . . . . . . . 5 66 5. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 5.1. The 'hlang-send' and 'hlang-recv' attributes . . . . . . 5 68 5.2. No Language in Common . . . . . . . . . . . . . . . . . . 7 69 5.3. Usage Notes . . . . . . . . . . . . . . . . . . . . . . . 7 70 5.4. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8 71 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 72 6.1. att-field Table in SDP Parameters . . . . . . . . . . . . 10 73 6.2. Warn-Codes Sub-Registry of SIP Parameters . . . . . . . . 11 74 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 75 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 11 76 9. Changes from Previous Versions . . . . . . . . . . . . . . . 11 77 9.1. Changes from draft-ietf-slim-...-04 to draft-ietf- 78 slim-...-06 . . . . . . . . . . . . . . . . . . . . . . . 11 79 9.2. Changes from draft-ietf-slim-...-02 to draft-ietf- 80 slim-...-03 . . . . . . . . . . . . . . . . . . . . . . . 12 81 9.3. Changes from draft-ietf-slim-...-01 to draft-ietf- 82 slim-...-02 . . . . . . . . . . . . . . . . . . . . . . . 12 83 9.4. Changes from draft-ietf-slim-...-00 to draft-ietf- 84 slim-...-01 . . . . . . . . . . . . . . . . . . . . . . . 12 85 9.5. Changes from draft-gellens-slim-...-03 to draft-ietf- 86 slim-...-00 . . . . . . . . . . . . . . . . . . . . . . . 12 87 9.6. Changes from draft-gellens-slim-...-02 to draft-gellens- 88 slim-...-03 . . . . . . . . . . . . . . . . . . . . . . . 12 89 9.7. Changes from draft-gellens-slim-...-01 to draft-gellens- 90 slim-...-02 . . . . . . . . . . . . . . . . . . . . . . . 13 91 9.8. Changes from draft-gellens-slim-...-00 to draft-gellens- 92 slim-...-01 . . . . . . . . . . . . . . . . . . . . . . . 13 93 9.9. Changes from draft-gellens-mmusic-...-02 to draft- 94 gellens-slim-...-00 . . . . . . . . . . . . . . . . . . . 13 95 9.10. Changes from draft-gellens-mmusic-...-01 to -02 . . . . . 13 96 9.11. Changes from draft-gellens-mmusic-...-00 to -01 . . . . . 13 97 9.12. Changes from draft-gellens-...-02 to draft-gellens- 98 mmusic-...-00 . . . . . . . . . . . . . . . . . . . . . . 14 99 9.13. Changes from draft-gellens-...-01 to -02 . . . . . . . . 14 100 9.14. Changes from draft-gellens-...-00 to -01 . . . . . . . . 15 101 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15 102 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 103 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 104 12.1. Normative References . . . . . . . . . . . . . . . . . . 15 105 12.2. Informational References . . . . . . . . . . . . . . . . 16 106 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 108 1. Introduction 110 A mutually comprehensible language is helpful for human 111 communication. This document addresses the negotiation of human 112 (natural) language and media modality (spoken, signed, written) in 113 real-time communications. A companion document [RFC8255] addresses 114 language selection in email. 116 Unless the caller and callee know each other or there is contextual 117 or out-of- band information from which the language(s) and media 118 modalities can be determined, there is a need for spoken, signed, or 119 written languages to be negotiated based on the caller's needs and 120 the callee's capabilities. This need applies to both emergency and 121 non-emergency calls. For example, it is helpful for a caller to a 122 company call center or a Public Safety Answering Point (PSAP) to be 123 able to indicate preferred signed, written, and/or spoken languages, 124 and for the callee to be able to indicate its capabilities in this 125 area, allowing the call to proceed using the language(s) and media 126 forms supported by both. 128 For various reasons, including the ability to establish multiple 129 streams using different media (e.g., voice, text, video), it makes 130 sense to use a per-stream negotiation mechanism known as the Session 131 Description Protocol (SDP). Utilizing Session Description Protocol 132 (SDP) [RFC4566] enables the solution described in this document to be 133 applied to all interactive communications negotiated using SDP, in 134 emergency as well as non-emergency scenarios. 136 By treating language as another SDP attribute that is negotiated 137 along with other aspects of a media stream, it becomes possible to 138 accommodate a range of users' needs and called party facilities. For 139 example, some users may be able to speak several languages, but have 140 a preference. Some called parties may support some of those 141 languages internally but require the use of a translation service for 142 others, or may have a limited number of call takers able to use 143 certain languages. Another example would be a user who is able to 144 speak but is deaf or hard-of-hearing and and desires a voice stream 145 to send spoken language plus a text stream to receive written 146 language. Making language a media attribute allows the standard 147 session negotiation mechanism to handle this by providing the 148 information and mechanism for the endpoints to make appropriate 149 decisions. 151 The term "negotiation" is used here rather than "indication" because 152 human language (spoken/written/signed) can be negotiated in the same 153 manner as media (audio/text/video) and codecs. For example, if we 154 think of a user calling an airline reservation center, the user may 155 have a set of languages he or she speaks, with perhaps preferences 156 for one or a few, while the airline reservation center will support a 157 fixed set of languages. Negotiation should select the user's most 158 preferred language that is supported by the call center. Both sides 159 should be aware of which language was negotiated. 161 In the offer/answer model used here, the offer contains a set of 162 languages per media (and direction) that the offerer is capable of 163 using, and the answer contains one language per media (and direction) 164 that the answerer will support. Supporting languages and/or 165 modalities can require taking extra steps, such as having a call 166 handled by an agent who speaks a requested language and/or with the 167 ability to use a requested modality, or bridging external translation 168 or relay resources into the call, etc. The answer indicates the 169 media and languages that the answerer is committing to support 170 (possibly after additional steps have been taken). This model also 171 provides knowledge so both ends know what has been negotiated. Note 172 that additional steps required to support the indicated languages or 173 modalities may or may not be in place in time for any early media. 175 Since this is a protocol mechanism, the user equipment (UE client) 176 needs to know the user's preferred languages; while this document 177 does not address how clients determine this, reasonable techniques 178 could include a configuration mechanism with a default of the 179 language of the user interface; in some cases, a UE could tie 180 language and media preferences, such as a preference for a video 181 stream using a signed language and/or a text or audio stream using a 182 written/spoken language. 184 1.1. Applicability 186 Within this document, it is assumed that the negotiating endpoints 187 have already been determined, so that a per-stream negotiation based 188 on the Session Description Protocol (SDP) can proceed. 190 When setting up interactive communications sessions it is necessary 191 to route signaling messages to the appropriate endpoint(s). This 192 document does not address the problem of language-based routing. 194 2. Terminology 196 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 197 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 198 "OPTIONAL" in this document are to be interpreted as described in BCP 199 14 RFC 8174 [RFC8174] when, and only when, they appear in all 200 capitals, as shown here. 202 3. Desired Semantics 204 The desired solution is a media attribute (preferably per direction) 205 that may be used within an offer to indicate the preferred 206 language(s) of each (direction of a) media stream, and within an 207 answer to indicate the accepted language. The semantics of including 208 multiple languages for a media stream within an offer is that the 209 languages are listed in order of preference. 211 (Negotiating multiple simultaneous languages within a media stream is 212 out of scope of this document.) 214 4. The existing 'lang' attribute 216 RFC 4566 [RFC4566] specifies an attribute 'lang' which appears 217 similar to what is needed here, but is not sufficiently specific or 218 flexible for the needs of this document. In addition, 'lang' is not 219 mentioned in [RFC3264] and there are no known implementations in SIP. 220 Further, it is useful to be able to specify language per direction 221 (sending and receiving). This document therefore defines two new 222 attributes. 224 5. Solution 226 An SDP attribute (per direction) seems the natural choice to 227 negotiate human (natural) language of an interactive media stream, 228 using the language tags of BCP 47 [RFC5646]. 230 5.1. The 'hlang-send' and 'hlang-recv' attributes 232 This document defines two media-level attributes starting with 233 'hlang' (short for "human interactive language") to negotiate which 234 human language is selected for use in each interactive media stream. 235 (Note that not all streams will necessarily be used.) There are two 236 attributes, one ending in "-send" and the other in "-recv", 237 registered in Section 6. Each can appear in offers and answers for 238 media streams. 240 In an offer, the 'hlang-send' value is a list of one or more 241 language(s) the offerer is willing to use when sending using the 242 media, and the 'hlang-recv' value is a list of one or more 243 language(s) the offerer is willing to use when receiving using the 244 media. The list of languages is in preference order (first is most 245 preferred). When a media is intended for interactive communication 246 using a language in one direction only (e.g., a user with difficulty 247 speaking but able to hear who indicates a desire to send using text 248 and receive using audio), either hlang-send or hlang-recv MAY be 249 omitted. When a media is not primarily intended for language (for 250 example, a video or audio stream intended for background only) both 251 SHOULD be omitted. Otherwise, both SHOULD have the same value. Note 252 that specifying different languages for each direction (as opposed to 253 the same or essentially the same language in different modalities) 254 can make it difficult to complete the call (e.g., specifying a desire 255 to send audio in Hungarian and receive audio in Portuguese). 257 In an answer, 'hlang-send' is the language the answerer will send if 258 using the media for language (which in most cases is one of the 259 languages in the offer's 'hlang-recv'), and 'hlang-recv' is the 260 language the answerer expects to receive if using the media for 261 language (which in most cases is one of the languages in the offer's 262 'hlang-send'). 264 In an offer, each value MUST be a list of one or more language tags 265 per BCP 47 [RFC5646], separated by white space. In an answer, each 266 value MUST be one language tag per BCP 47. BCP 47 describes 267 mechanisms for matching language tags. Note that [RFC5646] 268 Section 4.1 advises to "tag content wisely" and not include 269 unnecessary subtags. 271 When placing an emergency call, and in any other case where the 272 language cannot be inferred from context, in an offer each media 273 stream primarily intended for human language communication SHOULD 274 specify both (or for asymmetrical language use, one of) the 'hlang- 275 send' and 'hlang-recv' attributes. 277 Clients acting on behalf of end users are expected to set one or both 278 'hlang-send' and 'hlang-recv' attributes on each media stream 279 primarily intended for human communication in an offer when placing 280 an outgoing session, and either ignore or take into consideration the 281 attributes when receiving incoming calls, based on local 282 configuration and capabilities. Systems acting on behalf of call 283 centers and PSAPs are expected to take into account the attributes 284 when processing inbound calls. 286 Note that media and language negotiation might result in more media 287 streams being accepted than are needed by the users (e.g., if more 288 preferred and less preferred combinations of media and language are 289 all accepted). This is not a problem. 291 5.2. No Language in Common 293 A consideration with the ability to negotiate language is if the call 294 proceeds or fails if the callee does not support any of the languages 295 requested by the caller. This document does not mandate either 296 behavior. 298 If the call is rejected due to lack of any languages in common, it is 299 suggested to use SIP response code 488 (Not Acceptable Here) or 606 300 (Not Acceptable) [RFC3261] and include a Warning header field 301 [RFC3261] in the SIP response. The Warning header field contains a 302 warning code of [TBD: IANA VALUE, e.g., 308] and a warning text 303 indicating that there are no mutually-supported languages; the text 304 SHOULD also contain the supported languages and media. 306 Example: 308 Warning: [TBD: IANA VALUE, e.g., 308] proxy.example.com 309 "Incompatible language specification: Requested languages not 310 supported. Supported languages are: es, en; supported media 311 are: audio, text." 313 5.3. Usage Notes 315 A sign-language tag with a video media stream is interpreted as an 316 indication for sign language in the video stream. A non-sign- 317 language tag with a text media stream is interpreted as an indication 318 for written language in the text stream. A non-sign-language tag 319 with an audio media stream is interpreted as an indication for spoken 320 language in the audio stream. 322 This document does not define any other use for language tags in 323 video media (such as how to indicate visible captions in the video 324 stream). 326 In the IANA registry of language subtags per BCP 47 [RFC5646], a 327 language subtag with a Type field "extlang" combined with a Prefix 328 field value "sgn" indicates a sign-language tag. The absence of such 329 "sgn" prefix indicates a non-sign-language tag. 331 This document does not define the use of sign-language tags in text 332 or audio media. 334 This document does not define the use of language tags in media other 335 than interactive streams of audio, video, and text (such as "message" 336 or "application"). Such use could be supported by future work or by 337 application agreement. 339 5.4. Examples 341 Some examples are shown below. For clarity, only the most directly 342 relevant portions of the SDP block are shown. 344 An offer or answer indicating spoken English both ways: 346 m=audio 49170 RTP/AVP 0 347 a=hlang-send:en 348 a=hlang-recv:en 350 An offer indicating American Sign Language both ways: 352 m=video 51372 RTP/AVP 31 32 353 a=hlang-send:ase 354 a=hlang-recv:ase 356 An offer requesting spoken Spanish both ways (most preferred), spoken 357 Basque both ways (second preference), or spoken English both ways 358 (third preference): 360 m=audio 49250 RTP/AVP 20 361 a=hlang-send:es eu en 362 a=hlang-recv:es eu en 364 An answer to the above offer indicating spoken Spanish both ways: 366 m=audio 49250 RTP/AVP 20 367 a=hlang-send:es 368 a=hlang-recv:es 370 An alternative answer to the above offer indicating spoken Italian 371 both ways (as the callee does not support any of the requested 372 languages but chose to proceed with the call): 374 m=audio 49250 RTP/AVP 20 375 a=hlang-send:it 376 a=hlang-recv:it 378 An offer or answer indicating written Greek both ways: 380 m=text 45020 RTP/AVP 103 104 381 a=hlang-send:gr 382 a=hlang-recv:gr 384 An offer requesting the following media streams: video for the caller 385 to send using Argentine Sign Language, text for the caller to send 386 using written Spanish (most preferred) or written Portuguese, audio 387 for the caller to receive spoken Spanish (most preferred) or spoken 388 Portuguese: 390 m=video 51372 RTP/AVP 31 32 391 a=hlang-send:aed 393 m=text 45020 RTP/AVP 103 104 394 a=hlang-send:sp pt 396 m=audio 49250 RTP/AVP 20 397 a=hlang-recv:sp pt 399 An answer for the above offer, indicating text in which the callee 400 will receive written Spanish, and audio in which the callee will send 401 spoken Spanish. The answering party had no video capability: 403 m=video 0 RTP/AVP 31 32 404 m=text 45020 RTP/AVP 103 104 405 a=hlang-recv:sp 407 m=audio 49250 RTP/AVP 20 408 a=hlang-send:sp 410 An offer requesting the following media streams: text for the caller 411 to send using written English (most preferred) or written Spanish, 412 audio for the caller to receive spoken English (most preferred) or 413 spoken Spanish, supplemental video: 415 m=text 45020 RTP/AVP 103 104 416 a=hlang-send:en sp 418 m=audio 49250 RTP/AVP 20 419 a=hlang-recv:en sp 421 m=video 51372 RTP/AVP 31 32 423 An answer for the above offer, indicating text in which the callee 424 will receive written Spanish, audio in which the callee will send 425 spoken Spanish, and supplemental video: 427 m=text 45020 RTP/AVP 103 104 428 a=hlang-recv:sp 430 m=audio 49250 RTP/AVP 20 431 a=hlang-send:sp 432 m=video 51372 RTP/AVP 31 32 434 Note that, even though the examples show the same (or essentially the 435 same) language being used in both directions (even when the modality 436 differs), there is no requirement that this be the case. However, in 437 practice, doing so is likely to increase the chances of successful 438 matching. 440 6. IANA Considerations 442 6.1. att-field Table in SDP Parameters 444 IANA is kindly requested to add two entries to the 'att-field (media 445 level only)' table of the SDP parameters registry: 447 The first entry is for hlang-recv: 449 Attribute Name: hlang-recv 450 Contact Name: Randall Gellens 451 Contact Email Address: rg+ietf@coretechnologyconsulting.com 452 Attribute Value: hlang-value 453 Attribute Syntax: 455 hlang-value = hlang-offv / hlang-ansv 456 ; hlang-offv used in offers 457 ; hlang-ansv used in answers 458 hlang-offv = Language-Tag *( SP Language-Tag ) 459 ; Language-Tag as defined in BCP 47 460 SP = 1*" " ; one or more space (%x20) characters 461 hlang-ansv = Language-Tag 463 Attribute Semantics: Described in Section 5.1 of TBD: THIS 464 DOCUMENT 465 Usage Level: media 466 Mux Category: NORMAL 467 Charset Dependent: No 468 Purpose: See Section 5.1 of TBD: THIS DOCUMENT 469 O/A Procedures: See Section 5.1 of TBD: THIS DOCUMENT 470 Reference: TBD: THIS DOCUMENT 472 The second entry is for hlang-send: 474 Attribute Name: hlang-send 475 Contact Name: Randall Gellens 476 Contact Email Address: rg+ietf@coretechnologyconsulting.com 477 Attribute Value: hlang-value 478 Attribute Syntax: 480 hlang-value = hlang-offv / hlang-ansv 482 Attribute Semantics: Described in Section 5.1 of TBD: THIS 483 DOCUMENT 484 Usage Level: media 485 Mux Category: NORMAL 486 Charset Dependent: No 487 Purpose: See Section 5.1 of TBD: THIS DOCUMENT 488 O/A Procedures: See Section 5.1 of TBD: THIS DOCUMENT 489 Reference: TBD: THIS DOCUMENT 491 6.2. Warn-Codes Sub-Registry of SIP Parameters 493 IANA is requested to add a new value in the warn-codes sub-registry 494 of SIP parameters in the 300 through 329 range that is allocated for 495 indicating problems with keywords in the session description. The 496 reference is to this document. The warn text is "Incompatible 497 language specification: Requested languages not supported. Supported 498 languages and media are: [list of supported languages and media]." 500 7. Security Considerations 502 The Security Considerations of BCP 47 [RFC5646] apply here. In 503 addition, if the 'hlang-send' or 'hlang-recv' values are altered or 504 deleted en route, the session could fail or languages 505 incomprehensible to the caller could be selected; however, this is 506 also a risk if any SDP parameters are modified en route. 508 8. Privacy Considerations 510 Language and media information can suggest a user's nationality, 511 background, abilities, disabilities, etc. 513 9. Changes from Previous Versions 515 RFC EDITOR: Please remove this section prior to publication. 517 9.1. Changes from draft-ietf-slim-...-04 to draft-ietf-slim-...-06 519 o Deleted Section 3 ("Expected Use") 521 o Reworded modalities in Introduction from "voice, video, text" to 522 "spoken, signed, written" 524 o Reworded text about "increasingly fine-grained distinctions" to 525 instead merely point to BCP 47 Section 4.1's advice to "tag 526 content wisely" and not include unnecessary subtags 528 o Changed IANA registration of new SDP attributes to follow RFC 4566 529 template with extra fields suggested in 4566-bis (expired draft) 531 o Deleted "(known as voice carry over)" 533 o Changed textual instanced of RFC 5646 to BCP 47, although actual 534 reference remains RFC due to xml2rfc limitations 536 9.2. Changes from draft-ietf-slim-...-02 to draft-ietf-slim-...-03 538 o Added Examples 540 o Added Privacy Considerations section 542 o Other editorial changes for clarity 544 9.3. Changes from draft-ietf-slim-...-01 to draft-ietf-slim-...-02 546 o Deleted most of Section 4 and replaced with a very short summary 548 o Replaced "wishes to" with "is willing to" in Section 5.1 550 o Reworded description of attribute usage to clarify when to set 551 both, only one, or neither 553 o Deleted all uses of "IMS" 555 o Other editorial changes for clarity 557 9.4. Changes from draft-ietf-slim-...-00 to draft-ietf-slim-...-01 559 o Editorial changes to wording in Section 5. 561 9.5. Changes from draft-gellens-slim-...-03 to draft-ietf-slim-...-00 563 o Updated title to reflect WG adoption 565 9.6. Changes from draft-gellens-slim-...-02 to draft-gellens- 566 slim-...-03 568 o Removed Use Cases section, per face-to-face discussion at IETF 93 570 o Removed discussion of routing, per face-to-face discussion at IETF 571 93 573 9.7. Changes from draft-gellens-slim-...-01 to draft-gellens- 574 slim-...-02 576 o Updated NENA usage mention 578 o Removed background text reference to draft-saintandre-sip-xmpp- 579 chat-04 since that draft expired 581 9.8. Changes from draft-gellens-slim-...-00 to draft-gellens- 582 slim-...-01 584 o Revision to keep draft from expiring 586 9.9. Changes from draft-gellens-mmusic-...-02 to draft-gellens- 587 slim-...-00 589 o Changed name from -mmusic- to -slim- to reflect proposed WG name 591 o As a result of the face-to-face discussion in Toronto, the SDP vs 592 SIP issue was resolved by going back to SDP, taking out the SIP 593 hint, and converting what had been a set of alternate proposals 594 for various ways of doing it within SIP into an informative annex 595 section which includes background on why SDP is the proposal 597 o Added mention that enabling a mutually comprehensible language is 598 a general problem of which this document addresses the real-time 599 side, with reference to [RFC8255] which addresses the non-real- 600 time side. 602 9.10. Changes from draft-gellens-mmusic-...-01 to -02 604 o Added clarifying text on leaving attributes unset for media not 605 primarily intended for human language communication (e.g., 606 background audio or video). 608 o Added new section ("Alternative Proposal: Caller-prefs") 609 discussing use of SIP-level Caller-prefs instead of SDP-level. 611 9.11. Changes from draft-gellens-mmusic-...-00 to -01 613 o Relaxed language on setting -send and -receive to same values; 614 added text on leaving on empty to indicate asymmetric usage. 616 o Added text that clients on behalf of end users are expected to set 617 the attributes on outgoing calls and ignore on incoming calls 618 while systems on behalf of call centers and PSAPs are expected to 619 take the attributes into account when processing incoming calls. 621 9.12. Changes from draft-gellens-...-02 to draft-gellens-mmusic-...-00 623 o Updated text to refer to RFC 5646 rather than the IANA language 624 subtags registry directly. 626 o Moved discussion of existing 'lang' attribute out of "Proposed 627 Solution" section and into own section now that it is not part of 628 proposal. 630 o Updated text about existing 'lang' attribute. 632 o Added example use cases. 634 o Replaced proposed single 'hlang' attribute with 'hlang-send' and 635 'hlang-recv' per Harald's request/information that it was a misuse 636 of SDP to use the same attribute for sending and receiving. 638 o Added section describing usage being advisory vs required and text 639 in attribute section. 641 o Added section on SIP "hint" header (not yet nailed down between 642 new and existing header). 644 o Added text discussing usage in policy-based routing function or 645 use of SIP header "hint" if unable to do so. 647 o Added SHOULD that the value of the parameters stick to the largest 648 granularity of language tags. 650 o Added text to Introduction to be try and be more clear about 651 purpose of document and problem being solved. 653 o Many wording improvements and clarifications throughout the 654 document. 656 o Filled in Security Considerations. 658 o Filled in IANA Considerations. 660 o Added to Acknowledgments those who participated in the Orlando ad- 661 hoc discussion as well as those who participated in email 662 discussion and side one-on-one discussions. 664 9.13. Changes from draft-gellens-...-01 to -02 666 o Updated text for (possible) new attribute "hlang" to reference RFC 667 5646 669 o Added clarifying text for (possible) re-use of existing 'lang' 670 attribute saying that the registration would be updated to reflect 671 different semantics for multiple values for interactive versus 672 non-interactive media. 674 o Added clarifying text for (possible) new attribute "hlang" to 675 attempt to better describe the role of language tags in media in 676 an offer and an answer. 678 9.14. Changes from draft-gellens-...-00 to -01 680 o Changed name of (possible) new attribute from 'humlang" to "hlang" 681 o Added discussion of silly state (language not appropriate for 682 media type) 683 o Added Voice Carry Over example 684 o Added mention of multilingual people and multiple languages 685 o Minor text clarifications 687 10. Contributors 689 Gunnar Hellstrom deserves special mention for his reviews and 690 assistance. 692 11. Acknowledgments 694 Many thanks to Bernard Aboba, Harald Alvestrand, Flemming Andreasen, 695 Francois Audet, Eric Burger, Keith Drage, Doug Ewell, Christian 696 Groves, Andrew Hutton, Hadriel Kaplan, Ari Keranen, John Klensin, 697 Mirja Kuhlewind, Paul Kyzivat, John Levine, Alexey Melnikov, Addison 698 Phillips, James Polk, Eric Rescorla, Pete Resnick, Alvaro Retana, 699 Natasha Rooney, Brian Rosen, Peter Saint-Andre, and Dale Worley for 700 reviews, corrections, suggestions, and participating in in-person and 701 email discussions. 703 12. References 705 12.1. Normative References 707 [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, 708 A., Peterson, J., Sparks, R., Handley, M., and E. 709 Schooler, "SIP: Session Initiation Protocol", RFC 3261, 710 DOI 10.17487/RFC3261, June 2002, . 713 [RFC4566] Handley, M., Jacobson, V., and C. Perkins, "SDP: Session 714 Description Protocol", RFC 4566, DOI 10.17487/RFC4566, 715 July 2006, . 717 [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying 718 Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, 719 September 2009, . 721 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 722 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 723 May 2017, . 725 12.2. Informational References 727 [RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model 728 with Session Description Protocol (SDP)", RFC 3264, 729 DOI 10.17487/RFC3264, June 2002, . 732 [RFC8255] Tomkinson, N. and N. Borenstein, "Multiple Language 733 Content Type", RFC 8255, DOI 10.17487/RFC8255, October 734 2017, . 736 Author's Address 738 Randall Gellens 739 Core Technology Consulting 741 Email: rg+ietf@coretechnologyconsulting.com 742 URI: http://www.coretechnologyconsulting.com