Configuring Peer Resynchronization - Juniper JUNOSE 11.1.X - BROADBAND ACCESS CONFIGURATION GUIDE 6-4-2010 Configuration Manual

Configuring Peer Resynchronization

The JUNOSe software enables you to configure the peer resynchronization method
you want the router to use. Peer resynchronization enables L2TP to recover from a
router warm start and to allow an L2TP failed endpoint to resynchronize with its
peer non-failed endpoint.
L2TP peer resynchronization:
To ensure successful peer resynchronization between endpoints, the non-failed
endpoint must support a complete RFC-compliant L2TP implementation.
JUNOSe software supports both the L2TP silent failover method and the L2TP failover
protocol method, which is described in Fail Over extensions for L2TP "failover"
draft-ietf-l2tpext-failover-06.txt. You can configure L2TP to use the failover protocol
method as the primary peer resynchronization method, but then fall back to the
silent failover method if the peer does not support the failover protocol method.
The following list highlights differences between the failover protocol and silent
failover peer resynchronization methods:
NOTE: L2TP silent failover is not supported on E3 ATM and CT1 line modules in
peer-facing configurations.
Prevents the non-failed endpoint from prematurely terminating a tunnel while
the failed endpoint is recovering
Reestablishes the sequence numbers required for the operation of the L2TP
control protocol
Resolves inconsistencies in the tunnel and session databases of the failed endpoint
and the non-failed endpoint
With the L2TP failover protocol method, both endpoints must support the method
or recovery always fails. The L2TP failover protocol method also requires a
non-failed endpoint to wait an additional recovery time period while the failed
endpoint is recovering to prevent the non-failed endpoint from prematurely
disconnecting the tunnel. The additional recovery period makes L2TP less
responsive to the loss of tunnel connectivity.
Silent failover operates entirely within the failed endpoint and does not require
non-failed endpoint support this improves interoperability between peers. Silent
failover does not require additional recovery time by the non-failed endpoint,
which also eliminates the potential for degraded responsiveness to the loss of
tunnel connectivity.
Chapter 13: Configuring an L2TP LNS
Configuring Peer Resynchronization
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