Which characteristic of BFD provides rapid link-failure detection with minimal resource use?

Bidirectional Forwarding Detection (BFD) is designed to provide rapid detection of forwarding path failures between two systems. Its key characteristic for achieving this is using short duration timers, which means it sends frequent, small "hello" packets. This allows for quick detection of a lost connection, often within milliseconds, significantly faster than typical routing protocol hello timers. Despite the frequent packets, BFD is considered to have low overhead because the packets themselves are very small and require minimal processing resources from the network devices. This combination of short duration and low overhead makes BFD an efficient solution for fast fault detection. Long duration timers would lead to slower detection, while high overhead would consume excessive network and device resources, defeating BFD's purpose of efficient, rapid detection.