Controlling High-Bandwidth Flows at the Congested Router

FIFO queueing is simple but does not protect traffic from flows that send more than their share or flows that fail to use end-to-end congestion control. At the other extreme, per-flow scheduling mechanisms provide max-min fairness but are more complex, keeping state for all flows going through the router. This paper proposes RED-PD (RED with Preferential Dropping), a flow-based mechanism that combines simplicity and protection by keeping state for just the high-bandwidth flows. RED-PD uses the packet drop history at the router to detect high-bandwidth flows in times of congestion and preferentially drop packets from these flows. This paper discusses the design decisions underlying RED-PD, and presents simulations evaluating RED-PD in a range of environments. d Ratul is reachable at [email protected], and is also affiliated with the University of Washington. e Sally is reachable at [email protected].