Early Fair Drop A New Bu er Management Policy

In this paper we investigate the e ectiveness of packet drop mechanisms in conjunction with fair queuing link scheduling and hierarchical link sharing Under fair queuing the link share of a ow changes dynamically due to the arrivals and departures of ows 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 ows such as TCP that are expected to adjust their rates to the ows changing fair share of the link bandwidth We show experimentally that under the existing drop policies including random early detection and per ow schemes such as the longest queue drop implemented with fair scheduling policies TCP ows 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 ows adapt to their changing fair share of the link bandwidth when competing with di erent types of cross tra c e g bandwidth adaptive rate controlled greedy and on o We also illustrate that our drop policy provides isolation and fairness to ows other than TCP e g rate controlled on o