(Optional) Configuring LDP Graceful Deletion

LDP graceful deletion can be configured to speed up traffic switching using LDP-IGP synchronization, which improves network reliability.

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 physical and protocol status of the primary link is proper but the LDP session on the primary link goes Down, LDP-IGP synchronization enables LDP to inform the IGP of the primary link fault, and the IGP advertises the maximum cost value for the primary link. LDP then immediately instructs the upstream device to withdraw labels and assigns labels to the upstream device because a new LSP is established on the secondary link, which prolongs the LSP convergence time. As a result, packet loss occurs.

After the LDP session on the faulty link goes Down, LDP does not immediately instruct the upstream device to withdraw labels but keeps the labels and LSP and allows traffic to be transmitted on the primary link until the LSP convergence is complete on the secondary link. This ensures uninterrupted traffic and speeds up LDP-IGP synchronization.

Perform the following steps on the LDP-IGP synchronization-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, LDP does not instruct the upstream device to withdraw labels until 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.