This value, in milliseconds, sets how often RSVP Hello messages are sent on this interface to detect neighbor liveness, and per the description it only applies when gmplsInterfaceSignalingCaps has no bits set or includes the rsvpGmpls bit. An admin tunes it to control how quickly the device notices a failed RSVP neighbor versus the overhead of frequent hello traffic, and a value of 0 disables Hello messages on that interface entirely. For example, the MIB's own default of 3000 ms sends a Hello roughly every 3 seconds to each RSVP-GMPLS neighbor on that interface.