LSP setup protection using facility backup fast reroute

The facility-backup fast reroute mechanism has been extended to provide setup protection for LSPs that are in the process of being signaled. This feature is applicable in the following scenario:1. A failed link or node is present on the strict explicit path of an LSP before the LSP is signaled.2. There is also a bypass LSP protecting the link or node.3. RSVP signals the LSP through the bypass LSP. The LSP appears as if it was originally set up along its primary path and then failed over to the bypass LSP because of the link or node failure.4. When the link or node has recovered, the LSP can be automatically reverted to the primary path.