graceful-delete

Function

The graceful-delete command enables LDP graceful deletion.

The undo graceful-delete command disables LDP graceful deletion.

By default, LDP graceful deletion is disabled.

Format

graceful-delete

undo graceful-delete

Parameters

None

Views

MPLS LDP view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

This command is used to resolve the problems in the following scenarios:

In the scenario where links are not backed up, when a non-physical link fault occurs and the LDP session goes Down, if the device immediately instructs the upstream device to withdraw labels, the upstream device will be informed of the fault and the entire network will become unstable.
In the LDP-IGP synchronization scenario, if the physical and protocol status of the primary link is proper but the LDP session on the primary link goes Down, LDP-Interior Gateway Protocol (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 LDP graceful deletion is configured, the preceding problems can be resolved. After the LDP session goes Down, LDP does not immediately instruct the upstream device to withdraw labels but keeps the LSP until LSP switchover is complete, ensuring uninterrupted traffic and preventing LDP LSP flapping on the entire network.

Prerequisites

The mpls ldp (system view) command is used globally to enable MPLS LDP.

Follow-up Procedure

Run the graceful-delete timer command to set the delay value after which LDP instructs the upstream device to withdraw labels.

Example

# Enable LDP graceful deletion.

<sysname> system-view

[sysname] mpls ldp

[sysname-mpls-ldp] graceful-delete