Detour backup establishes backup path with detour sessions from point of local repair (PLR) to merge point (MP).
RSVP FRR LSP with detour backup applies the same algorithm for the backup path computation. The algorithm is designed to follow RFCs to avoid various issues intrinsic to detour backup type such as early session merging and bandwidth sharing.
Note
Fusion devices support FRR failover for RSVP LSPs. If the point of failure is a transit router with respect to the LSP path, then failover can be performed (LSP is repaired, and traffic flow restored) very quickly, in less than 50 milliseconds. When the point of failure is ingress router with respect to the LSP path, FRR failover is not quick enough and it may take more than 50 milliseconds to repair the LSP. Traffic loss will be more than 50 milliseconds.