mpls te soft-preemption (MPLS view)

Function

The mpls te soft-preemption command enables soft preemption for all RSVP-TE tunnels on the ingress.

The undo mpls te soft-preemption command disables soft preemption for all RSVP-TE tunnels on the ingress.

By default, this function is disabled globally. If soft preemption is disabled globally but enabled in the view of a specified local tunnel interface, the local tunnel is capable of this function.

Format

mpls te soft-preemption

undo mpls te soft-preemption

Parameters

None

Views

MPLS view

Default Level

2: Configuration level

Task Name and Operations

Task Name	Operations
mpls-te	write

Usage Guidelines

Usage Scenario

The setup and holding priorities and the preemption function are configured to allow TE tunnels to be established preferentially to transmit important services, preventing random resource competition during tunnel establishment.

If there is no path meeting the bandwidth requirement of a desired tunnel, a device can tear down an established tunnel and use bandwidth resources assigned to that tunnel to establish a desired tunnel. This is called preemption. The following preemption modes are supported:

Hard preemption: A tunnel with a higher setup priority can preempt resources assigned to a tunnel with a lower holding priority. Consequently, some traffic is dropped on the tunnel with a lower holding priority during the hard preemption process.
Soft preemption: After a tunnel with a higher setup priority preempts the bandwidth of a tunnel with a lower holding priority, the soft preemption function retains the tunnel with a lower holding priority for a specified period of time. If the ingress finds a better path for this tunnel after the time elapses, the ingress uses the make-before-break (MBB) mechanism to reestablish the tunnel over the new path. If the ingress fails to find a better path after the time elapses, the tunnel goes Down.
To enable soft preemption, run the mpls te soft-preemption command.

Prerequisites

MPLS TE has been enabled globally using the mpls te command.

Configuration Impact

The priority and preemption attributes are used in conjunction to determine resource preemption among tunnels. If multiple tunnels are to be established, tunnels with higher setup priorities can be established by preempting resources. If resources, such as bandwidth, are insufficient, a tunnel with a higher setup priority can preempt resources of an established tunnel with a lower holding priority.

Precautions

After the preceding configuration, the device performs soft preemption for tunnels that meet the following conditions:

P2P tunnels that use RSVP-TE as a signaling protocol: include manual tunnels, manual bypass tunnels, auto tunnels, auto bypass tunnels, IP-prefix tunnel, and auto tunnels delivered by a PCE server.
Manual tunnels whose tunnel interfaces have no mpls te soft-preemption block, mpls te resv-style ff command run.
If the mpls te soft-preemption command has been run in the view of the manual tunnel interface, this configuration prevails.

Example

# Configure soft preemption for all RSVP-TE tunnels.

<HUAWEI> system-view
[~HUAWEI] mpls
[*HUAWEI-mpls] mpls te
[*HUAWEI-mpls] mpls te soft-preemption