Priorities and preemption are used to allow TE tunnels to be established preferentially to transmit important services, preventing 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 CR-LSP with a higher setup priority can directly preempt resources assigned to a CR-LSP with a lower holding priority. Some traffic is dropped on the CR-LSP with a lower holding priority during the hard preemption process.
- Soft preemption: After a CR-LSP with a higher setup priority preempts bandwidth of a CR-LSP with a lower holding priority, the soft preemption function retains the CR-LSP with a lower holding priority for a specified period of time. If the ingress finds a better path for this CR-LSP after the time elapses, the ingress uses the make-before-break mechanism to reestablish the CR-LSP over the new path. If the ingress fails to find a better path after the time elapses, the CR-LSP goes down.
Procedure
- Configure soft preemption in the P2MP TE tunnel template view.
- Run system-view
The system view is displayed.
- Run mpls te p2mp-template template-name
The P2MP TE tunnel template view is displayed.
- Run soft-preemption
Soft preemption is enabled for the P2MP TE tunnel.
- Run commit
The configuration is committed.
- Configure soft preemption in the P2MP TE tunnel view.
- Run system-view
The system view is displayed.
- Run interface tunnel tunnel-number
The P2MP TE tunnel interface view is displayed.
- Run mpls te soft-preemption
Soft preemption is enabled.
- Run commit
The configuration is committed.