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.
Context
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.
Procedure
- Configure software preemption in the RSVP-TE tunnel interface view.
- Run system-view
The system view is displayed.
- Run interface interface-type interface-number
The interface view is displayed.
- Run tunnel-protocol mpls te
MPLS TE is configured as a tunneling protocol.
- (Optional) Run mpls te signal-protocol rsvp-te
A signaling protocol is configured for the tunnel.
By default, the signaling protocol of a tunnel is RSVP-TE.
- Run mpls te soft-preemption
Software preemption is configured in the RSVP-TE tunnel interface view.
- Run commit
The configuration is committed.
- Configure software preemption in the MPLS view.
- Run system-view
The system view is displayed.
- Run mpls
The MPLS view is displayed.
- Run mpls te
MPLS TE is globally enabled.
- Run mpls rsvp-te
RSVP-TE is enabled.
- Run mpls te soft-preemption
Software preemption is configured in the MPLS view.
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: including manual tunnels, manual bypass tunnels, auto tunnels, auto bypass tunnels, IP-prefix tunnel, and auto tunnels delivered by a PCE controller.
Manual tunnels whose tunnel interfaces have no mpls te soft-preemption block or mpls te resv-style ff command configured.
If the mpls te soft-preemption command has been run in the view of the manual tunnel interface, this configuration prevails.
- Run commit
The configuration is committed.