(Optional) Configuring LDP Graceful Deletion
Context
LDP graceful deletion can be configured in the synchronization between LDP and IGP or LDP FRR 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, Synchronization between LDP and IGP enables LDP to inform the IGP of the primary link fault, and the IGP configures the maximum cost value for the primary link. LDP then 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 synchronization between LDP and IGP.
Perform the following steps on the LSR configured with synchronization between LDP and IGP.
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 time
The value of the graceful deletion timer is set.
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 LSPs will be kept for a long time, consuming system resources.
- Run commit
The configuration is committed.
