A flow control method and system including an algorithm for deciding to transmit an arriving packet into a processing queue or to discard it, or, in the case of instructions or packets that must not be discarded, a similar method and system for deciding at a service event to transmit an instruction or packet into a processing queue or to skip the service event. The transmit probability is increased or decreased in consideration of minimum and maximum limits for each flow, aggregate limits for sets of flows, relative priority among flows, queue occupancy, and rate of change of queue occupancy. The effects include protection of flows below their minimum rates, correction of flows above their maximum rates, and, for flows between minimum and maximum rates, reduction of constituent flows of an aggregate that is above its aggregate maximum. Practice of the invention results in low queue occupancy during steady congestion.