[Ecrit] Drafts on real-time text of interest for ECRIT

["Gunnar Hellstrom" <[e-mail]>]

A point has been included in the ECRIT agenda on drafts for real-time text
handling.
 
This is a brief description of the drafts and motivation for presenting them
in ECRIT.
 
 
Title: Real-time text refinements
 
Presenter: Gunnar Hellstrom
 
Drafts: 
draft-hellstrom-text-conference-01
draft-hellstrom-textpreview-06
draft-hellstrom-text-turntaking-02
draft-hellstrom-textgwy-01
 
 
Links:
http://www.ietf.org/internet-drafts/draft-hellstrom-text-conference-01.txt

 <http://www.ietf.org/internet-drafts/draft-hellstrom-textpreview-06.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-textpreview-06.txt

 
<http://www.ietf.org/internet-drafts/draft-hellstrom-text-turntaking-02.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-text-turntaking-02.txt

 <http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt

Motivation:

Consistent presentation of RFC 4103 real-time text media in SIP sessions
have become essential by its adoption for emergency services in the IETF
ECRIT specifications. Therefore, specifications are needed that nail down
presentation related details so that the view of a text conversation can be
maintained in synchronism at the participants of a session.

One use case is when a relay service is included in the call for translation
between a text conversation with the user and a spoken conversation with the
PSAP, still presenting also the typed dialogue to the PSAP. This scenario
requires a three-party call handling of the real-time text as well as other
media in the call. Text can be used as a single medium in a call, or in
various combinations with video and audio to carry all from the whole
dialogue to small pieces of information that is easier to transfer by text
than by audio or video. 

The following drafts will be presented. The basic information on the use of
real-time text is found in RFC 4103, RFC 5194, RFC 5012,
draft-ietf-ecrit-phonebcp and draft-ietf-ecrit-framework.

1. draft-hellstrom-text-conference-01 gives details on how to use the RTP
translator model and the mixer model for multi-party conferences with
real-time text. Both models have their pros and cons. The translator model
requires no specific marking in the media stream, but instead advanced RTP
handling of multiple SSRC:s in the same RTP session that all RTP
implementations MUST have but in practice seldom has. The mixer model
requires new source marking at the media level but simpler RTP handling. It
is proposed to agree on the use of one of these methods.

2. draft-hellstrom-textpreview-06 gives details on how real-time text
sessions can be presented, and adds details on the scope of erasure and
division of text into paragraphs or messages. These clarifications are
important to keep a common view of a text conversation for the participants.


3. draft-hellstrom-text-turntaking-02 is a registration of a media feature
tag of importance for smooth interoperation with legacy text communication
protocols. Gateways to legacy text communication is important where the
emergency services provide access for legacy text terminals. The feature tag
is needed because the legacy equipment has functional limitations in
simultaneity that the SIP user must consider when in contact with legacy
equipment.
 
4. draft-hellstrom-textgwy-01  specifies call control and media handling for
gateways for real-time text between SIP with RFC 4103 for text  and PSTN
with textphones such as TTY. Gateways to legacy text communication is
important where the emergency services provide access for legacy text
terminals.
 
 
More information on the drafts:
 
----------------------------------------------------------------------------
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1. Title : Text media handling in RTP based real-time conferences

Author(s) : G. Hellstrom, A. Wijk

Filename : draft-hellstrom-text-conference-01.txt

Pages : 9

Date : 2009-07-12

This memo specifies methods for text media handling in multi-party calls,
where the text is carried by the RTP protocol. Real-time text is carried in
a time-sampled mode according to RFC 4103. Centralized multi-party handling
of real-time text is achieved through a media control unit coordinating
multiple RTP text streams into one RTP session, identifying each stream with
its own SSRC. Identification for the streams are provided through the RTCP
messages. This mechanism enables the receiving application to present the
received real-time text medium in different ways according to user
preferences. Some presentation related features are also described
explaining suitable variations of transmission and presentation of text.
Call control features are described for the SIP environment, while the
transport mechanisms should be suitable for any IP based call control
environment using RTP transport. An alternative method using a single RTP
stream and source identification inline in the text stream is also
described.

A URL for this Internet-Draft is:

 
<http://www.ietf.org/internet-drafts/draft-hellstrom-text-conference-01.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-text-conference-01.txt

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

2. Title : Presentation of Text Conversation in realtime and en-bloc form

Author(s) : G. Hellstrom, et al.

Filename : draft-hellstrom-textpreview-06.txt

Pages : 17

Date : 2009-07-11

This specification defines methods for presentation of a text conversation
with focus on the real-time features. The aim is to give the participants in
a conversation a good opportunity to perceive the real-time flow of the
conversation and also provide a display of the history of the conversation
that makes it easy to read. Both two-party and multi-party situations are
defined.

A URL for this Internet-Draft is:

 <http://www.ietf.org/internet-drafts/draft-hellstrom-textpreview-06.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-textpreview-06.txt

----------------------------------------------------------------------------
-----------
 
3 Title : Registration of the Real-time-text Media Feature Tag

Author(s) : G. Hellstrom, A. Wijk

Filename : draft-hellstrom-text-turntaking-02.txt

Pages : 6

Date : 2009-07-12

This memo defines a new Media Feature Tag "real-time-text" for use in SIP
registration and session establishment. This is used to indicate if a device
capable of text communication has full real-time text capabilities or
limitations in its capabilities requiring the users to apply some
turn-taking habits.

A URL for this Internet-Draft is:

 
<http://www.ietf.org/internet-drafts/draft-hellstrom-text-turntaking-02.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-text-turntaking-02.txt

----------------------------------------------------------------------------
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4. Title : Real-time text interworking between PSTN and IP networks

Author(s) : G. Hellstrom, et al.

Filename : draft-hellstrom-txtgwy-01.txt

Pages : 16

Date : 2009-07-13

IP networks can support real-time text communication. SIP-based

real- time text is called Text-over-IP or ToIP. PSTN networks support
real-time text using textphones (or TTYs). When real-time text is supported
by different networks, gateways are needed to provide interoperability.
Real-time text capable gateways may also support real-time voice.

This specification describes procedures for interworking between ToIP and
PSTN textphones using a real-time text capable gateway (RTT gateway). It
also describes ways to route calls to RTT gateways for several call
scenarios.

Procedures that support the phased introduction of RTT gateways and
procedures that support the invocation of text channels at any time during
the call are included. Interworking of PSTN textphones that do not support
simultaneity of voice and text with IP User Agents that support simultaneous
voice and text is also described.

A URL for this Internet-Draft is:

 <http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt

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The drafts have not got any working group assignments yet. They are of
interest for ECRIT, but probably not of such central interest that they
should be made ECRIT working group items.
 
/Gunnar
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Gunnar Hellström
Omnitor
[e-mail]
Tel: [phone]
www.omnitor.se <http://www.omnitor.se/>