3.5.5.1.1.2 Dynamic Behavior

At the start of each round (triggered by the expiration of the Block timer) in the Pausing state, a responder MUST sample its random number generator and choose a time that is uniformly distributed between 0 and N times I. If the chosen time is less than Tb, the responder MUST set the Hello timer to the chosen time. If the time is greater than or equal to Tb, the responder MUST NOT send a Hello frame in this round (because the Hello timer will not expire during the round).

During the block, the responder MUST count the Hello and Discover messages on the network (including its own transmission if any) in the variable r, so at the end of the block, the responder can use this information to update its estimate of the number of active responders, as specified in section 3.5.6.2.