This PositiveInteger sets how many seconds of missed Hello packets must elapse before neighbors declare this router down, and it should be some multiple of the Hello interval and must match across all routers on a common network. Setting it too short causes flapping adjacencies over a jittery link; too long delays failure detection. An admin running OSPF over a lossy wireless backhaul would raise this value, along with a proportionally larger Hello interval, to tolerate occasional missed hellos.