A network device monitors the traffic of individual flows through one of its ingress ports and, if the traffic volume exceeds a predetermined threshold, signals for a reduction in data traffic volume transmitted to that ingress port from one or more source devices. Example signals may include without limitation a unicast congestion message sent to the source of a flow, an Explicit Congestion Notification to one or more source devices, and the dropping of packets by the receiving device. In response to such signals, one or more of the source devices decrease the transmission rate of data traffic to the receiving device.