Refer to the exhibit.

BFD is the correct design feature for detecting a link failure within 200 ms or less without materially increasing OSPF control-plane load. Cisco uses Bidirectional Forwarding Detection as a fast, lightweight failure-detection protocol that can be associated with routing protocols such as OSPF. Instead of relying on aggressive OSPF hello and dead timers, BFD performs rapid forwarding-path checks and notifies OSPF when the path fails. This allows fast convergence while avoiding the additional routing-protocol overhead and instability that can come from very low hello timers. UDLD detects unidirectional Layer 2 fiber failures, but it is not the routing adjacency failure-detection mechanism requested here. Carrier delay can adjust interface state transition timing, but it does not provide a routing-protocol independent liveness session. Fast hellos can reduce detection time, but they increase protocol traffic and can affect overall performance. BFD is therefore the proper design choice for fast and efficient OSPF convergence. Reference topics: BFD, OSPF convergence, fast failure detection, routed campus resiliency, control-plane efficiency.