A data processing device for transmitting network packets comprising: packet classification logic for classifying packets according to different packet service classifications, wherein a packet to be transmitted is stored in one or more transmit queues based on the packet service classifications and wherein each packet is associated with a particular flow; and queue management logic for queuing packets in the one or more transmit queues utilizing a flow control policy implemented on a per-flow basis, wherein a number of queued packets for each flow is monitored and when the number of queued packets for a particular flow reaches a specified threshold, then flow control for that particular flow is turned on, and wherein the queue management logic implements a stochastic fair blue (SFB) algorithm to track the number of packets within each transmit queue.