Subject: I-D ACTION:draft-leurs-megaco-t38-callflows-00.txt

From: [email-masked]
Date: Fri, 08 Nov 2002 07:33:31 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: Procedures for Megaco/H.248 controlled Voice Media 
                          Gateways for Autonomous Switchover to Fax Relay 
                          Service
	Author(s)	: A. Leurs, C. Waitzmann, A. Schwarz
	Filename	: draft-leurs-megaco-t38-callflows-00.txt
	Pages		: 27
	Date		: 2002-11-7
	
This document describes the handling of realtime fax calls in
Megaco/H.248 controlled MGs. The call setup and capability
negotiation is done with support of the control domain with Megaco
commands. The switch over to fax or modem, upon detection of the
relevant tones, is done in an autonomous way, without intervention
of the control domain.
In the Appendix, the Megaco messages for a call setup scenario with
capability negotiation are shown, to point out the structure of the
to the transmitting MG. Switching to T.38 is done after reception of
V.21 flags.
In the other flows, T.38 is not enabled, both MGs switch to the
fallback case, fax pass-through mode.
This document is based on the superior framework (reference [2]).
The reader should be familiar with [2].
SDP sessions in the local and remote descriptors.
Call flow diagrams are given as example:
In the first flow, a T.30 CNG tone is generated by the transmitting
terminal, the transmitting MG signals the detection towards the
receiving MG. Switching to T.38 is done by both MGs as soon as
possible.
In the second example, a T.30 CED tone is sent by the receiving
terminal. As this tone is no clear indication that a FAX will be
sent, the receiving MG will switch to VBD after signaling this event

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