Global revertive mode: The head-end LSR of each tunnel is responsible for reoptimizing the TE LSPs that used the failed resource. There are several potential reoptimization triggers: RSVP error messages, inspection of OSPF LSAs or ISIS LSPs, and timers. Note that this re-optimization process may proceed as soon as the failure is detected. It is not tied to the restoration of the failed resource. Local revertive mode: Upon detecting that the resource is restored, the PLR re-signals each of the TE LSPs that used to be routed over the restored resource. Every TE LSP successfully re-signaled along the restored resource is switched back.