Internet DRAFT - draft-hellstrom-slim-modality-grouping
draft-hellstrom-slim-modality-grouping
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
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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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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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