By default an LSP is established based on manual and/or CSPF constraints and remains within this state until a topology change occurs or a new LSP is established through some sort of failure or manual intervention. The objective of LSP optimisation is to provide a periodic timer that that allows CSPF computations to be applied to specific LSPs over the period of the that’s specified in the optimisation timer.
The benefit of this feature is to allow LSPs to become aware of new resources that may become available in the network. For example, should a new link be added to the IGP SFP database, LSPs would not become aware of these new resources unless optimisation is used.
The optimisation timer is configured at an LSP level and can be applied within a range of 0-65535. The default timer is 0 which means no optimisation is used. It is generally considered best practice to vary the optimisation timers for different LSPs; this allows for recomputation at different intervals, reducing load on the control plane.