Current congestion control approaches that attempt to provide fair bandwidth allocation among competing flows primarily consider only data rate when making decisions on which packets to drop. However, responsive flows with high round-trip times (RTTs) can still receive significantly less bandwidth than responsive flows with low round-trip times. Better bandwidth fairness control can avoid expensive Content Distribution Network deployment cost because CDNs provide improved, uniform performance to all clients regardless of proximity and can improve utilization in the same circumstances. This paper proposes an enhancement to AQM schemes called FIFA that addresses router unfairness in handling flows with significantly different RTTs. Using a best-case estimate of a flowu27s RTT provided in each packet by the flow source or by an edge router, FIFA computes a stabilized average RTT. The average RTT is then compared with the RTT of each incoming packet, dynamically adjusting the drop probability so as to protect the bandwidth of flows with high RTTs while curtailing the bandwidth of flows with low RTTs. We present simulation resutls and analysis that demonstrate FIFA on top of any AQM schemes improves fairness without sacrificing throughput.
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