In this paper, we first evaluate the performance of recent TCP variants for high-speed and long-delay networks in IEEE 802.11 wireless LAN environment through simulation experiments. We show that some of them still have well-known TCP unfairness property between uplink and downlink flows, and that there is another unfairness problem among uplink flows caused by the loss-based behavior of hybrid TCP variants. We then propose an end-to-end-basis modification to TCP congestion control mechanisms to alleviate the unfairness problems, which activates the congestion control when detecting ACK packet losses. Through simulation experiments, we present that the proposed method is effective not only for TCP fairness among uplink flows but also for fairness between uplink and downlink flows, while keeping the total throughput to be large enough.
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