THOMSON SpeedTouch, Configuration Manual, Page: 99 / 110

Chapter 10
Routed PPPoI
E-DOC-CTC-20051017-0167 v1.0
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10.3 ISDN Callback
ISDN Backup
The SpeedTouch™ has an ISDN interface that can be used to create an ISDN backup
for the ADSL line. The process is shown in the diagram below:
When the ADSL line fails, the SpeedTouch™ establishes a dial-in connection
towards the ISDN network. A PPP connection is then established over this ISDN
connection which takes over the traffic from the failed ADSL line.
ISDN Callback
If the SpeedTouch™ establishes the ISDN connection from the user end, the user
will be charged with the connection cost. To avoid this, it is possible to use the
callback option (if the other end supports it).
The SpeedTouch™ establishes a dial in connection and provides all necessary
information, and disconnects. The system then waits for a callback to establish the
ISDN connection over which the PPP connection is established.
This is typical for connections which are governed by a Service Level Agreement
(SLA).
More Information
For more information, refer to the WAN Fallback Application Note.
Dial-In Modes
The dial in connection line can operate in one of two modes:
Always on: the backup connection is always on
Dial on demand: the backup connection is established when necessary, i.e.
when the ADSL line fails.
Configuring Callback
In order to configure callback, you need to do the following:
1
Configure the ISDN Dial-In Connection
2
Configure the PPP connection
INTERNET
I S DN
AD S L
I S DN