(Optional) Configuring LDP Graceful Deletion

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

Context

LDP graceful deletion can be configured in the LDP-IGP synchronization scenario to speed up traffic switching and ensure uninterrupted traffic during traffic switching, improving 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 configures the maximum cost value for the primary link. After that, LDP immediately instructs the upstream device to withdraw labels and allocates labels to the upstream device because a new LSP is set up on the secondary link, prolonging 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 the LDP-IGP synchronization.

Perform the following operations on the LSR configured with LDP-IGP synchronization.

Procedure

Access the system view.
```
system-view
```
Access the MPLS LDP view.
```
mpls ldp
```
Enable LDP graceful deletion.
```
graceful-delete
```
(Optional) Set the value of the graceful deletion timer.
```
graceful-delete timer time
```
After the LDP session goes Down, LDP does not instruct the upstream device to withdraw labels until the graceful deletion timer expires.

By default, the value of the graceful deletion timer is 5 seconds.

If the value of the graceful deletion timer is too large, the invalid LSP will be kept for a long time, consuming system resources.