You can develop a preemption strategy whereby a new LSP can claim resources from an existing LSP. Each tunnel can be configured with a setup priority and a hold priority. Priority levels range from 0 (highest priority) through 7 (lowest priority).
If traffic engineering admission control determines that there are insufficient resources to accept a request to set up a new LSP, the setup priority is evaluated against the hold priority of existing LSPs. An LSP with a hold priority lower than the setup priority of the new LSP can be preempted. The existing LSP is terminated to make room (free resources) for the new LSP. You must assign priorities according to network policies to prevent resource poaching and LSP thrashing.