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RE: Fwd: RTT note in WebRTC 1.0

From: Scott Hollier <scott@hollier.info>
Date: Wed, 9 Oct 2019 12:08:06 +0000
To: Janina Sajka <janina@rednote.net>, Judy Brewer <jbrewer@w3.org>
CC: RQTF <public-rqtf@w3.org>, Dominique Hazael-Massieux <dom@w3.org>
Message-ID: <SN6PR01MB43499E64DA5206B8C63A99FEDC950@SN6PR01MB4349.prod.exchangelabs.com>
To Janina

Seems really clear to me, good work!


Dr Scott Hollier 
Digital Access Specialist 
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-----Original Message-----
From: Janina Sajka <janina@rednote.net> 
Sent: Wednesday, 9 October 2019 5:58 PM
To: Judy Brewer <jbrewer@w3.org>
Cc: RQTF <public-rqtf@w3.org>; Dominique Hazael-Massieux <dom@w3.org>
Subject: Re: Fwd: RTT note in WebRTC 1.0

Hello All:

I have revised Dom's text somewhat and included suggested language from Josh. Before we send this out to APA for approval, can we please determine I have improved the language--and not impaired it!

Accessibility considerations [New section, informative]

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

Real-time Text, defined in RFC 4103 on which people who are deaf or hard of hearing (among others) rely on for their communication needs, utilizes T.140 encapsulated in RTP to enable the transition from TDD/TTY devices to IP-based communications. Support for RFC 4103 is especially important is it is being established as the new and more reliable mechanism for text communications with emergency service centers.

Since Real-time Text requires the ability to send and receive data in near real time, it can be 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 channels. 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 this publication there is no standardized way for the WebRTC APIs to directly support Real-time Text as defined at IETF and implemented in U.S. (FCC) regulations.  The WebRTC working group will be actively looking to address this gap in future specification revisions, as well as at progressing technical API requirements.  We hope to do this in conjunction with developing IETF protocols.

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.


As of this publication polyfill implementations exist that do enable effective RTT support in WebRTC applications. This is deemed sufficient until such time as future gateways are enabled via IETF protocols such as the SCTP data channel protocol and RFC 4103 Real-time text. This will need to be defined at IETF in conjunction with related work at W3C groups to effectively and consistently standardise RTT support internationally.




Janina Sajka

Linux Foundation Fellow
Executive Chair, Accessibility Workgroup:	http://a11y.org

The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Chair, Accessible Platform Architectures	http://www.w3.org/wai/apa
Received on Wednesday, 9 October 2019 12:08:11 UTC

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