Work out failover time budget instantly with clear inputs, formula shown and shareable results.
Failover time is the sum of detection, convergence and service warm-up, and detection is often the hidden cost: default BFD or keepalive timers of several seconds set a floor no amount of fast routing can beat. Sub-second failover requires aggressive detection intervals, which trade against false positives from transient loss.
Failover budget
total = detection + convergence + service restart; slack = RTO - total
BFD with intervals of tens of milliseconds, or link-state notification from the physical layer. Application-level health checks every 30 seconds cannot support fast failover.
Short timers interpret brief congestion or a control-plane hiccup as a failure, causing unnecessary failovers that are themselves disruptive.