This counts the number of MPLS Fast Reroute detour LSPs entering this device, but only reports a meaningful non-zero value when the router is configured for the one-to-one backup protection method -- it always reads zero if facility backup is configured instead. This distinction matters operationally because one-to-one backup creates an individual detour LSP per protected LSP, scaling with LSP count, while facility backup uses a shared bypass tunnel for many LSPs at once, so this counter is specifically useless for gauging FRR protection load on a facility-backup-configured router, and an admin must check the configured protection method before trusting this number. A router protecting 200 individual LSPs under one-to-one backup might show this object at 200, while a neighboring router protecting the same 200 LSPs under facility backup would show this object as a flat 0 despite providing equivalent protection.