Which mechanism provides faster OSPF reconvergence without the CPU cost of reducing hello and dead timers?

Bidirectional Forwarding Detection (BFD) is a lightweight, low-overhead protocol that provides rapid fault detection for forwarding paths. It operates independently of the routing protocol (like OSPF) and can detect failures in milliseconds, significantly faster than typical OSPF hello/dead timer intervals. This allows OSPF to reconverge much more quickly without needing to reduce its own timers, which can consume more CPU and bandwidth. SSO (Stateful Switchover) is a high-availability feature for redundant hardware, not a reconvergence mechanism for routing protocols. Dead Peer Detection (DPD) keepalives are used in IPsec VPNs to detect dead peers, not for general OSPF reconvergence. OSPF demand circuits are used to suppress periodic hellos over expensive links, not to speed up reconvergence.