(Optional) Configuring LDP Graceful Deletion

LDP graceful deletion can be configured to speed up LDP FRR traffic switching.

Context

LDP graceful deletion can be configured in the LDP-IGP synchronization or LDP FRR scenario to speed up traffic switching. It helps uninterruptedly transmit traffic during traffic switching, which improves reliability of the entire network.

If the primary link goes Down and the LDP session on the primary link also goes Down, LDP immediately instructs the upstream device to withdraw labels and triggers LDP Auto FRR. LSP convergence on the secondary link requires LDP to assign labels to the upstream device again, which prolongs the convergence time and FRR traffic switching. As a result, packet loss occurs.

If LDP graceful deletion is configured and the LDP session goes Down, LDP delays deleting the LDP session and keeps the relevant labels and LSP. The LSP on the secondary link does not require LDP to assign labels to the upstream device again, which shortens FRR traffic switching and reduces packet loss.

Perform the following steps on the LDP FRR-enabled LSR:

Procedure

Run system-view
The system view is displayed.
Run mpls ldp
The MPLS-LDP view is displayed.
Run graceful-delete
LDP graceful deletion is enabled.
(Optional) Run graceful-delete timer timer
The graceful deletion timer value is set.

After the LDP session goes Down, forwarding entries on the LSR remain before the graceful deletion timer expires.

If the graceful deletion timer value is too large, the invalid LSP will be kept for a long time, which consumes system resources.
Run commit
The configurations are committed.