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Versions: (draft-hellstrom-language-grouping) 00 01

SLIM                                                        G. Hellstrom
Internet-Draft                                                   Omnitor
Intended status: Standards Track                         January 3, 2018
Expires: July 7, 2018


   Human Language Modality Grouping Semantics in Session Description
                                Protocol
               draft-hellstrom-slim-modality-grouping-01

Abstract

   When setting up a real-time communication session, there may be a
   need to indicate preference for which media and modality (spoken,
   written or signed) to use for language communications or a need to
   indicate preference for receiving the same language content
   simultaneously in two modalities.  This document defines the
   semantics for grouping media for such purposes in the Session
   Description Protocol (SDP).  The semantics defined in this document
   are based on the SDP Grouping Framework.  Applications are for
   example negotiation the most suitable common modality or modalities
   for language communications in a real-time session.  The indications
   are specified for the sending and receiving direction separately.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on July 7, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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   (https://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Requirements for Modality Grouping  . . . . . . . . . . . . .   4
     3.1.  Simultaneous Use of Different Modalities  . . . . . . . .   4
     3.2.  Preference for Language in Different Modality . . . . . .   4
   4.  Modality Grouping . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Simultaneous Use of Different Modalities  . . . . . . . .   4
     4.2.  Preference for Language in Different Modality . . . . . .   5
   5.  SDP Offer/Answer Considerations . . . . . . . . . . . . . . .   5
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  Desire by caller to receive both spoken and written
           language form of media  . . . . . . . . . . . . . . . . .   6
     6.2.  High preference by caller to receive sign language and
           lower preference for text.  . . . . . . . . . . . . . . .   7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   10. Changes from earlier versions . . . . . . . . . . . . . . . .   9
     10.1.  Changes from draft-hellstrom-slim-modality-grouping-00
            to draft-hellstrom-slim-modality-grouping-01 . . . . . .   9
     10.2.  Changes from draft-hellstrom-language-grouping-00 to
            draft-hellstrom-slim-modality-grouping-00  . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     11.2.  Informative References . . . . . . . . . . . . . . . . .  10
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   In certain applications it is of interest to indicate a need for, or
   the availability of, transformed version of the contents of a media
   stream in another media and modality, while still also providing the
   original.

   The application may for example be for indication of rapid subtitling
   of speech either manually or automatically.  It may also be for
   indication of sign language interpretation of speech, or spoken




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   interpretation of sign language when both the original and the
   interpretation is delivered to the user.

   This specification defines an indication that language contents in
   one modality is desired simultaneously with a different modality.
   The mechanism used is based on the Session Description Protocol (SDP)
   Grouping Framework [RFC5888] and used with SDP [RFC4566].  The same
   indication is used for indication of preparedness to send language
   contents in one modality simultaneously with same content in a
   different modality.

   When starting a conversation in a media-rich environment, the users
   may have very specific preferences for using one modality (spoken,
   written or signed) over other possible but less preferred modalities.
   In traditional call establishment, it is the answering part who is
   expected to start the conversation by a greeting.  In the media-rich
   environment, the modality and language of this greeting sets the
   expectations for what modality and language to mainly use in the
   session.  Deviation from this initial expectation is usually possible
   during the session by mutual agreement between the participants, but
   may be time consuming and cause uncertainty.

   A way for the parties to thoroughly describe the desired language
   communication for a session as well as providing information about
   less preferred alternatives is specified.  The indication includes
   information of alternative languages and modalities for the
   communication directions in the session, and also indication of
   preference for specific modalities per direction.  This specification
   defines a mechanism for indicating modality preference based on the
   Session Description Protocol (SDP) Grouping Framework [RFC5888].

   The expected application area is wide.  By old tradition, the most
   common modality for real-time interaction is spoken communication.
   In some settings, e.g. where silence is required, it may be desirable
   to express a preference for using written communication, while still
   leaving a possibility open for traditional spoken communication by an
   indication on lower preference level.  For persons having full
   ability to both use sign language and spoken language, but not
   wanting to force the other party to bring in a sign language
   interpreter in the call, it may be of importance to be able to
   indicate the sign language capability on a lower preference level and
   the spoken language capability on a higher level.  Some persons may
   strongly prefer to conduct a written conversation, while still
   wanting to express that a spoken conversation is possible as a last
   resort.  Many other situations exist in the media-rich communication
   environment when the modality preference indication is of value for a
   smooth initiation of a real-time session.




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   The mechanisms for specifying simultaneous use of language in
   different modalities and preference between modalities specified in
   this document may be combined with a mechanism for specifying
   language use in media specified in other documents.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Requirements for Modality Grouping

3.1.  Simultaneous Use of Different Modalities

   The grouping semantics for indication of simultaneous use of
   different media for different transforms of the same language shall
   have the ability to indicate:

   o  That the language contents of one media is desired or offered also
      simultaneously in a transformed form in other media grouped with
      the first.

   o  The direction of language communication that the indication is
      valid for; sending or receiving as seen from the party providing
      the SDP.

3.2.  Preference for Language in Different Modality

   The grouping semantics for indication of relative preference between
   use for language communication in different media and modalities
   shall have the ability to indicate:

   o  The order of preference for receiving or providing language
      contents in the media included in a grouping.

   o  The direction of language communication that the indication is
      valid for; sending or receiving as seen from the party providing
      the SDP.

4.  Modality Grouping

4.1.  Simultaneous Use of Different Modalities

   The "Human Language Simultaneous Send" (HLSS) and "Human Language
   Simultaneous Receive" (HLSR) grouping semantics and the SDP "group"
   attribute defined in [RFC5888] are used to associate media in which
   it is indicated that different transforms of the same content is



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   either desired to be received by a party or offered for sending by a
   party.

   The "a=group:HLSS" semantics SHOULD be used to indicate media
   grouping for preparedness for sending of same language contents in
   different transforms in all media included in the group.

   The "a=group:HLSR" semantics SHOULD be used to indicate media
   grouping for preference for reception of language contents in
   different transforms in all media in the group.

   The HLSS and HLSR semantics MAY be used together with mechanisms for
   detailing language use in media.  One such mechanism is
   [I-D.ietf-slim-negotiating-human-language].

4.2.  Preference for Language in Different Modality

   The "Human Language Preferred Send" (HLPS) and "Human Language
   Preferred Receive" (HLPR) grouping semantics and the SDP "group"
   attribute defined in [RFC5888] are used to associate media among
   which it is indicated an order of preference for using the media for
   language contents.  The order of preference is that the media
   identity first in the group has highest preference and the following
   have lower preference in the same order as they appear in the group
   definition.

   The "a=group:HLPS" semantics SHOULD be used to indicate media
   grouping for preparedness for sending of language contents with
   preference in the same order as the media identities appear in the
   group with the first having highest preference.

   The "a=group:HLPR" semantics SHOULD be used to indicate media
   grouping for preference for reception of language contents with
   preference in the same order as the media identities appear in the
   group with the first having highest preference.

   The HLPS and HLPR semantics MAY be used together with mechanisms for
   detailing language use in media.  One such mechanism is
   [I-D.ietf-slim-negotiating-human-language].

5.  SDP Offer/Answer Considerations

   The following SDP offer/answer considerations according to [RFC3264]
   apply.

   An application that understands the received HLSR, HLSS, HLPR or HLPS
   grouping semantics SHOULD make efforts to satisfy the preferences
   expressed by the grouping semantic.



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   The answer SHOULD include HLSR, HLSS, HLPR or HLPS grouping semantics
   corresponding to what the answering application prefers to receive
   and what the answering application is prepared to send, best matching
   the received preference indications and its own capabilities.  The
   answering party SHOULD make best effort to transmit language contents
   in media and modality according to the answer.

   The offering party SHOULD analyze the answer and make best effort to
   transmit language contents in media according to the answer.

   The grouping semantics defined in this document are only informing
   about language contents disposition in media and SHOULD NOT be taken
   as reasons to enable or reject media streams.

   Media not included in any HLPR or HLPS grouping are assumed to be
   assigned lower preference for being used for language communication
   than the ones included in HLPR or HLPS grouping.

   If the HLSR, HLSS, HLPR or HLPS grouping semantics are used without
   any further language specifications, video media SHOULD be assumed to
   be used for sign language, audio media for spoken language and text
   media for written language.

   Note that grouping of "m" lines MUST always be requested by the
   offerer, but never by the answerer.  Since SIP provides a two-way SDP
   exchange, an answerer that requested grouping would not know whether
   the "group" attribute was accepted by the offerer or not.  An
   answerer that wants to group media lines SHOULD issue another offer
   after having responded to the first one (in a re-INVITE, for
   instance).

6.  Examples

6.1.  Desire by caller to receive both spoken and written language form
      of media

      v=0

      o=Laura 289083124 289083124 IN IP4 two.example.com

      c=IN IP4 233.252.0.1/127

      t=0 0

      a=group:HLSR 1 2

      m=audio 30000 RTP/AVP 0




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      a=mid:1

      m=text 30002 RTP/AVP 98 97

      a=mid:2

      m=video 30004 RTP/AVP 34

      a=mid:3

   Note that also the video media needs to include a 'mid' attribute
   even when it is not included in any grouping for the grouping to be
   valid.

   An answer can confirm that both desired media will contain the same
   language contents.

      v=0

      o=Laura 289083124 289083124 IN IP4 two.example.com

      c=IN IP4 233.252.0.1/127

      t=0 0

      a=group:HLSS 1 2

      m=audio 30000 RTP/AVP 0

      a=mid:1

      m=text 30002 RTP/AVP 98 97

      a=mid:2

      m=video 30004 RTP/AVP 34

      a=mid:3

6.2.  High preference by caller to receive sign language and lower
      preference for text.

      v=0

      o=Laura 289083124 289083124 IN IP4 two.example.com

      c=IN IP4 233.252.0.1/127




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      t=0 0

      a=group:HLPR 3 2

      m=audio 30000 RTP/AVP 0

      a=mid:1

      m=text 30002 RTP/AVP 98 97

      a=mid:2

      m=video 30004 RTP/AVP 34

      a=mid:3

   Note that also the audio media needs to include a 'mid' attribute
   even when it is not included in any grouping for the grouping to be
   valid.

   An answer can confirm that sign language will be sent in the video
   media.

      v=0

      o=Laura 289083124 289083124 IN IP4 two.example.com

      c=IN IP4 233.252.0.1/127

      t=0 0

      a=group:HLPS 3

      m=audio 30000 RTP/AVP 0

      a=mid:1

      m=text 30002 RTP/AVP 98 97

      a=mid:2

      m=video 30004 RTP/AVP 34

      a=mid:3







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7.  Acknowledgements

   -

8.  IANA Considerations

   IANA is kindly requested to register the following semantics in the
   "Semantics for the "group" SDP Attribute" registry under SDP
   Parameters:

      Semantics Token Reference

      ---------------------------------- ----- ---------

      Human Language Simultaneous Send HLSS TBD: THIS DOCUMENT

      Human Language Simultaneous Receive HLSS TBD: THIS DOCUMENT

      Human Language Preference Send HLPS TBD: THIS DOCUMENT

      Human Language Preference Receive HLPR TBD: THIS DOCUMENT

9.  Security Considerations

   Modality preference information may belong to the kind of sensitive
   user information that some users do not want to be presented to
   anyone.  Measures for protection against unauthorized access to the
   modality preference information should therefore be prepared and
   activated when so required.  Intended callees should be regarded to
   be authorized to access the callers modality preference information.
   The modality preference information should be treated with similar
   security and privacy measures as other user information such as
   addresses and language preferences.

10.  Changes from earlier versions

   RFC EDITOR: Please remove this section prior to publication.

10.1.  Changes from draft-hellstrom-slim-modality-grouping-00 to draft-
       hellstrom-slim-modality-grouping-01

   Corrections of some spelling mistakes.

   Simplification of some sentences.







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10.2.  Changes from draft-hellstrom-language-grouping-00 to draft-
       hellstrom-slim-modality-grouping-00

   Changed name to indicate that this draft has relations to the IETF
   SLIM WG.

   Shortened abstract.

   changed to more polite IANA considerations.

   Introduced a section with changes from earlier versions.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3264]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
              with Session Description Protocol (SDP)", RFC 3264,
              DOI 10.17487/RFC3264, June 2002,
              <https://www.rfc-editor.org/info/rfc3264>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <https://www.rfc-editor.org/info/rfc4566>.

   [RFC5888]  Camarillo, G. and H. Schulzrinne, "The Session Description
              Protocol (SDP) Grouping Framework", RFC 5888,
              DOI 10.17487/RFC5888, June 2010,
              <https://www.rfc-editor.org/info/rfc5888>.

11.2.  Informative References

   [I-D.ietf-slim-negotiating-human-language]
              Gellens, R., "Negotiating Human Language in Real-Time
              Communications", draft-ietf-slim-negotiating-human-
              language-19 (work in progress), December 2017.

Author's Address








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   Gunnar Hellstrom
   Omnitor
   Hammarby Fabriksvag 23
   Stockholm  SE-120 30
   Sweden

   Phone: +46 708 204 288
   Email: gunnar.hellstrom@omnitor.se











































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