User`s guide

110 XSR User’s Guide
Configuring PPP with a Dialed Backup Line Chapter 6
Configuring PPP
The BACP protocol must reach the Opened state using the standard PPP
mechanism as defined in RFC-1661. Once BACP reaches the Opened state on
a bundle, BAP may transmit packets through this PPP/MLPPP pipeline.
BAP datagrams are encapsulated by the PPP/MLPPP module and
transmitted across the link. Transmission and reception of BAP and BACP
packets is through the same interface procedures used by any other NCP
protocol pair.
Functionality provided by BAP/BACP is summarized as follows:
 To add links:
– Negotiate phone numbers over the bundles through BAP.
– Agree with peer before trying to set up a call.
– Check for available lines before agreeing to add a link.
– Manage race conditions when both peers wish to add a link.
 To delete links:
– Agree with peer to tear down a link before disconnecting the call.
Configuring PPP with a Dialed Backup Line
You can configure PPP on the following types of physical interfaces:
 Asynchronous serial
 Synchronous serial
 T1/E1
By enabling PPP encapsulation on physical interfaces, PPP can also be used
on calls placed by the dialer interfaces that use the physical interfaces. Refer
to Figure 13 for an example of an XSR configured with one backup dial line to
two different sites.