Real-time text interworking between PSTN and IP networks

Document Type Expired Internet-Draft (individual)
Authors Gunnar Hellstrom  , Barry Dingle  , Arnoud Wijk  , Guido Gybels 
Last updated 2010-03-08
Stream (None)
Intended RFC status (None)
Expired & archived
pdf htmlized (tools) htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state Expired
Telechat date
Responsible AD (None)
Send notices to (None)

This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


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.


Gunnar Hellstrom (
Barry Dingle (
Arnoud Wijk (
Guido Gybels (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)