Early fair drop: a new buffer management policy
John L. Bruno, Banu Özden, Abraham Silberschatz, Huzur Saran · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1998
In this paper, we investigate the effectiveness of packet- drop mechanisms in conjunction with fair queuing link scheduling and hierarchical link sharing. Under fair queuing, the link share of a flow changes dynamically due to the arrivals and departures of flows and their bursts. This phenomenon becomes more pronounced in the case of hierarchical link sharing. Packet-drop mechanisms play an integral role for bandwidth-adaptive flows, such as TCP, that are expected to adjust their rates to the flows' changing fair share of the link bandwidth. We show experimentally that, under the existing drop policies (including random early detection and per-flow schemes such as the longest-queue drop) implemented with fair scheduling policies, TCP flows are slow to adjust their rates to their changing share of the link bandwidth. To overcome this problem, we propose a new packet-drop policy that simultaneously exploits two dimensions--when to drop and what to drop. We demonstrate that, under our packet-drop policy and with fair queuing, TCP flows adapt to their changing fair share of the link bandwidth when competing with different types of cross-traffic (e.g., bandwidth adaptive, rate controlled, greedy and on-off). We also illustrate that our drop policy provides isolation and fairness to flows other than TCP (e.g., rate controlled, on- off).