User`s guide

142 XSR User’s Guide
Implementing Dial Services Chapter 8
Configuring Dialer Services
PPP is the encapsulation method of choice for Dialer Services because it
supports multiple protocols and is used for synchronous or asynchronous
connections. Also, PPP performs address negotiation and authentication and
is interoperable with different vendors.
ISDN Callback
ISDN callback funtionality, also known as dial-back, is a Dial on Demand
application to handle ISDN call charge billing. The benefit of this feature is, if
a caller contacts the XSR, the router will try to call back a pre-configured
number, and in the process reverse the associated charge. A maximum of 32
caller numbers can be set per Dialer port.
ISDN callback is supported for PPP or Multilink PPP traffic and can be
applied in a backup scenario if the retry number is set to 1.
Configured with the
dialer caller <number> callback command, the
functionality employs caller ID screening with ISDN callback to accept calls
from a specified phone number. The XSR matches phone numbers starting
with the last digit.
Typically the ISDN switch does not provide the complete calling number,
only the local number (four to seven of the least significant digits).
NOTE
If the ISDN switch does not provide the calling number, callback will fail.
Callback can be configured in point-to-point or point-to-multipoint
applications with one or multiple neighbors. A neighbor in this context is
considered one hop away from the XSR.
Refer to “Configuring ISDN Callback” on page 148 for configuration
examples.