Subject: [dispatch] Real-time text interworking between PSTN and IP networks

From: "Gunnar Hellstrom" <[email-masked]>
Date: Wed, 22 Jul 2009 09:55:34 +0200

A new draft is available at
 <http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt>
http://www.ietf.org/internet-drafts/draft-hellstrom-txtgwy-01.txt

When a feature is offered in one network, it is important to offer
interoperability with other networks. 

Even if real-time text in IP networks overshadow what was avialable in PSTN
in terms of functionality, it is still possible to arrange interoperability
between real-time text in IP networks with the different forms of text
telephony that are available in PSTN networks ( e.g. TTY, EDT, V.21 based,
DTMF based etc ).  Issues on many levels appear when such interoperability
shall be arranged. e.g. on routing, media negotiating, indications to the
users, handling the limitations in media simultaneity in PSTN in contrast
with the full simultaneity possible in IP etc. 

The draft gives guidance on many of these topics and can be seen as an
expansion on this topic from what was specified in RFC 5194..

In my view, it is a typical SIPPING topic, so therefore I turn to Dispatch
with the question of where to discuss it.

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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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Gunnar Hellström
Omnitor
[email-masked]
Tel: +46708204288
www.omnitor.se <http://www.omnitor.se/>