Fwd: RTT note in WebRTC 1.0

FYI, forwarding the text, per discussion in RQTF this morning.

- Judy

-------- Forwarded Message --------
Subject:  RTT note in WebRTC 1.0
Date:  Wed, 25 Sep 2019 08:43:10 +0200
From:  Dominique Hazael-Massieux <dom@w3.org>
To:  Judy Brewer <jbrewer@w3.org>
CC:  Bernard Aboba <Bernard.Aboba@microsoft.com>



Hi Judy,

As part of the discussion with the APA WG last Friday [1], we discussed
the possibility of adding an informative note to the WebRTC 1.0 spec
(before its imminent publication as a hopefully-last Candidate
Recommendation) that would discuss our understanding of how RTT can be
today used in combination with WebRTC and point to work that could
enable more in depth integration.

I'm including here is some proposed initial text to that effect that
Bernard (cpoied) and I came up with, with input from Harald as well.

Could you review it to ensure it would address your concern with regard
to demonstrating W3C's cognizance on the topic and informing on existing
work in this space and W3C's future plans?

My plan is to turn that text into a pull request to the WebRTC spec, and
post it for review to the APA WG ASAP.

Thanks,

----------------
Accessibility considerations [New section, informative]

The WebRTC 1.0 specification exposes an API to control protocols
(defined within the IETF) necessary to the establishment of real-time
audio, video and data exchange.

Real-time Text, defined in RFC 4103 and on which among others, people
with disabilities rely on for their communication needs, utilizes T.140
encapsulated in RTP to enable the transition from TDD/TTY devices to
IP-based communications.

Since Real-time Text requires the ability to send and receive data, it
is best supported via the WebRTC 1.0 data channel API. As defined by
the IETF, the data channel protocol utilizes the SCTP/DTLS/UDP protocol
stack, which supports both reliable and unreliable data channel. The
IETF chose to standardize SCTP/DTLS/UDP over proposals for an RTP data
channel which relied on SRTP key management and were focused on
unreliable communications.

Since the IETF chose a different approach than the RTP data channel as
part of the WebRTC suite of protocols, as of the time of the publication
of the WebRTC 1.0 specification, there is no standardized way for the
WebRTC APIs to directly support Real-time Text.

Within the IETF MMUSIC WG, work is ongoing to enable Real-time text to
be sent over the WebRTC data channel, allowing gateways to be deployed
to translate between the SCTP data channel protocol and RFC 4103
Real-time text. This work, once completed, would enable a unified and
interoperable approach for integrating real-time text in WebRTC
user-agents (including browsers) - through a gateway or otherwise.

MMUSIC-T140:
https://tools.ietf.org/html/draft-holmberg-mmusic-t140-usage-data-channel

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

Dom

1. https://www.w3.org/2019/09/20-apa-minutes.html#item02

-- 
Judy Brewer
Director, Web Accessibility Initiative
at the World Wide Web Consortium (W3C)
105 Broadway, Room 7-128, MIT/CSAIL
Cambridge MA 02142 USA
www.w3.org/WAI/