One document matched: draft-gellens-negotiating-human-language-00.txt
MMUSIC Working Group R. Gellens
Internet-Draft Qualcomm Technologies, Inc.
Intended status: Standards Track February 15, 2013
Expires: August 17, 2013
Negotiating Human Language Using SDP
draft-gellens-negotiating-human-language-00
Abstract
Users have various human language needs, abilities, and preferences
regarding spoken, written, and signed languages. When establishing
interactive communication "calls" there needs to be a way to
communicate and ideally match (i.e., negotiate) the caller's needs,
abilities, and preferences with the capabilities of the called party.
This is especially important with emergency calling, where a call can
be routed to a PSAP or call taker capable of communicating with the
user, or a translator or relay operator can be bridged into the call
during setup, but this applies to non-emergency calls as well (as an
example, when calling an airline reservation desk).
This document describes the need and expected use, and discusses the
solution using either an existing or new SDP attribute.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on August 17, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
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Internet-Draft Negotiating Human Language February 2013
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Expected Use . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Desired Semantics . . . . . . . . . . . . . . . . . . . . . . 4
5. Proposed Solution . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Possibility: Re-Use existing 'lang' attribute . . . . . . 4
5.2. Possibility: Define new 'humlang' attribute . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . . 6
8.2. Informational References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
When setting up interactive communication sessions, human (natural)
language negotiation is needed in some cases. When the caller and
callee are known to each other or where context implies language,
such language negotiation may not be needed. In other cases, there
is a need for the caller to indicate language preferences, abilities,
or needs, including specific spoken, signed, or written languages.
This need exists when setting up SIP sessions (including emergency
and non-emergency calling). For various reasons, including the
ability to establish multiple streams each using a different media
(e.g., voice, text, video), it makes sense to use a per-stream
negotiation mechanism, using SDP.
This approach has a number of benefits, including that it is generic
and not limited to emergency calls. In some cases such a facility
isn't needed, because the language is known from the context (such as
when a caller places a call to a sign language relay center). But it
seems clearly useful in many other cases. For example, it seems
generally useful that someone calling a company call center be able
to indicate if a specific sign and/or spoken language is needed. The
UE would need to set this, but could default to the language used for
the interface with the user.
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Including the user's natural language requirements in the session
establishment negotiation is independent of the use of a relay
service and is transparent to a voice service provider. For example,
assume a user within the United States who speaks Spanish but not
English places a voice call using an IMS device. It doesn't matter
if the call is an emergency call or not (e.g., to an airline
reservation desk). The language information is transparent to the
carrier, but is part of the session negotiation between the UE and
the terminating entity. In the case of a call to e.g., an airline,
the call can be automatically routed to a Spanish-speaking agent. In
the case of an emergency call, the ESInet and the PSAP may choose to
take the language into account when determining how to route and
process the call (e.g., language and media needs may be considered
within policy-based routing).
By treating language as another session attribute that is negotiated
along with media, it becomes possible to accommodate a wide range of
users' needs and called party facilities. For example, some users
may be able to speak several languages, but have a preference. Some
called parties may support some of those languages internally but
require the use of a bridged translation service for others. The
standard session negotiation mechanism handles this by providing the
information and mechanism for the endpoints to make appropriate
decisions.
Regarding relay services, in the case of an emergency call requiring
sign language such as ASL, there are two common approaches: the
caller initiates the call to a relay center, or the caller places the
call to emergency services (e.g., 911 or 112). In the former case,
the language need is ancillary and supplemental. In the latter case,
the ESInet and/or PSAP may take the need for sign language into
account and bridge in a relay center. In this case, the ESInet and
PSAP have all the standard information available (such as location)
but are able to bridge the relay sooner in the call processing.
By making this facility part of the end-to-end negotiation, the
question of which entity provides or engages the relay service
becomes separate from the call processing mechanics; if the caller
directs the call to a relay service then the natural language
facility provides extra information to the relay service but calls
will still function without it; if the caller directs the call to
emergency services, then the ESInet/PSAP are able to take the user's
natural language needs into account, e.g., by routing to a particular
PSAP or call taker or bridging a relay service or translator.
The term "negotiation" is used here rather than "indication" because
human language (spoken/written/signed) is something that can be
negotiated in the same way as which forms of media (audio/text/video)
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or which codecs.
For example, if we think of non-emergency calls, such as a user
calling an airline reservation center, the user may have a set of
languages he or she speaks, with perhaps preferences for one or a
few, while the airline reservation center will support a fixed set of
languages. Negotiation should select whichever language supported by
the call center is most preferred by the user. Both sides should be
aware of which language was negotiated. This is conceptually similar
to the way other aspects of the session are negotiated using SDP
(e.g., media and codecs).
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 RFC 2119 [RFC2119].
3. Expected Use
This facility is expected to be used by NENA and 3GPP. NENA is
likely to reference it in NENA 08-01 (i3 Stage 3) in describing
attributes of calls presented to an ESInet, and in that or other
documents describing Policy-Based Routing capabilities within a
Policy-Based Routing Function (PCRF). 3GPP is expected to reference
this mechanism in general call handling and emergency call handling.
Recent CRs introduced in SA1 have anticipated this functionality
being provided within SDP.
4. Desired Semantics
The desired solution is a media attribute that may be used within an
offer to indicate preferred language(s) of each media stream, and
within an answer to indicate the accepted language. The semantics of
including multiple values for a media stream within an offer is that
the languages are listed in order of preference.
5. Proposed Solution
An SDP attribute seems the natural choice to negotiate human
(natural) language. The attribute value should be an IANA language
tag from the registry www.iana.org/assignments/language-subtag-
registry [1]
5.1. Possibility: Re-Use existing 'lang' attribute
RFC 4566 [RFC4566] specifies an attribute 'lang' which sounds similar
to what is needed here, the difference being that it specifies that
'a=lang' is declarative with the semantics of multiple 'lang'
attributes being that all of them are used, while we want a means to
negotiate which one is used in each stream. This difference means
that either the existing 'lang' attribute can't be used and we need
to define a new attribute, or we finese/update the semantics of
'lang' (or possibly the author has misunderstood RFC 4566).
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The text from RFC 4566 [RFC4566] is:
a=lang:<language tag>
This can be a session-level attribute or a media-level attribute.
As a session-level attribute, it specifies the default language
for the session being described. As a media- level attribute, it
specifies the language for that media, overriding any session-
level language specified. Multiple lang attributes can be
provided either at session or media level if the session
description or media use multiple languages, in which case the
order of the attributes indicates the order of importance of the
various languages in the session or media from most important to
least important.
The "lang" attribute value must be a single [RFC3066] language tag
in US-ASCII [RFC3066]. It is not dependent on the charset
attribute. A "lang" attribute SHOULD be specified when a session
is of sufficient scope to cross geographic boundaries where the
language of recipients cannot be assumed, or where the session is
in a different language from the locally assumed norm.
The question is: Can the 'lang' attribute be used for our purposes?
Using it to negotiate the language for a media seems at first glance
to violate its semantics as defined in RFC 4566 [RFC4566]. But there
are existing examples of it being used in exactly the way we need.
For example, draft-saintandre-sip-xmpp-chat-04 [I-D.saintandre-sip-
xmpp-chat] contains an example where the initial invitation contains
two 'a=lang' entries for a media stream (for English and Italian) and
the OK accepts one of them (Italian), which matches what we need:
Example: (F1) SIP user starts the session
INVITE sip:juliet@example.com SIP/2.0
To: <sip:juliet@example.com>
From: <sip:romeo@example.net>;tag=576
Subject: Open chat with Romeo?
Call-ID: 742507no
Content-Type: application/sdp
c=IN IP4 s2x.example.net
m=message 7313 TCP/MSRP *
a=accept-types:text/plain
a=lang:en
a=lang:it
a=path:msrp://s2x.example.net:7313/ansp71weztas;tcp
Example: (F2) Gateway accepts session on Juliet's behalf
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SIP/2.0 200 OK
To: <sip:juliet@example.com>;tag=534
From: <sip:romeo@example.net>;tag=576
Call-ID: 742507no
Content-Type: application/sdp
c=IN IP4 x2s.example.com
m=message 8763 TCP/MSRP *
a=accept-types:text/plain
a=lang:it
a=path:msrp://x2s.example.com:8763/lkjh37s2s20w2a;tcp
5.2. Possibility: Define new 'humlang' attribute
Instead of re-using 'lang' we may define a new media-level attribute
'humlang' to negotiate which human language is used in each media
stream:
a=humlang:<language tag>
This is a media-level attribute. In an offer, it specifies the
desired language(s) for the media. Multiple humlang attributes
can be provided in an offer for a media stream, in which case the
order of the attributes indicates the order of preference of the
various languages from most preferred to least preferred. Within
an answer it indicates the accepted language for the media.
The "humlang" attribute value must be a single [RFC3066] language
tag in US-ASCII [RFC3066]. It is not dependent on the charset
attribute. A "humlang" attribute SHOULD be specified when placing
an emergency call (to avoid ambiguity) or in any other case where
the language cannot be assumed from context.
6. IANA Considerations
TBD.
7. Security Considerations
TBD
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3066] Alvestrand, H., "Tags for the Identification of
Languages", RFC 3066, January 2001.
[RFC4566] Handley, M., Jacobson, V. and C. Perkins, "SDP: Session
Description Protocol", RFC 4566, July 2006.
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8.2. Informational References
[I-D.iab-privacy-considerations]
Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M. and R. Smith, "Privacy
Considerations for Internet Protocols", Internet-Draft
draft-iab-privacy-considerations-03, July 2012.
[I-D.saintandre-sip-xmpp-chat]
Saint-Andre, P., Gavita, E., Hossain, N. and S. Loreto,
"Interworking between the Session Initiation Protocol
(SIP) and the Extensible Messaging and Presence Protocol
(XMPP): One-to-One Text Chat", Internet-Draft draft-
saintandre-sip-xmpp-chat-04, October 2012.
Author's Address
Randall Gellens
Qualcomm Technologies, Inc.
5775 Morehouse Drive
San Diego, CA 92121
US
Email: rg+ietf@qti.qualcomm.com
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