Improving TCP fairness with the MarkMax policy

We introduce MarkMax a new flow-aware active queue management algorithm for additive increase multiplicative decreases protocols (like TCP). MarkMax sends a congestion signal to a selected connection whenever the total back-log reaches a given threshold. The selection mechanism is based on the state of large flows. Using a fluid model we derive some bounds that can be used to analyze the behavior of MarkMax and we compute the per-flow backlog. We conclude the paper with simulation results, using NS-2, comparing MarkMax with drop tail and showing how MarkMax improves both the fairness and link utilization when connections have significantly different round trip times.