After BFD for OSPF is enabled, if a link fails, the router rapidly detects the failure, notifies the OSPF process or interface of the fault, and instructs OSPF to recalculate routes. This speeds up OSPF network convergence.
OSPF enables the router to periodically send Hello packets to a neighboring router for fault detection. Detecting a fault takes more than 1s. As voice, video, and other VOD services are widely used. These services are sensitive to packet loss and delays. When traffic is transmitted at gigabit rates, long-time fault detection will cause packet loss. This cannot meet high reliability requirements of the carrier-class network. BFD for OSPF was introduced to resolve this problem. After BFD for OSPF is configured in a specified process or on a specified interface, the link status can be rapidly detected and fault detection can be completed in milliseconds. This speeds up OSPF convergence when the link status changes.