保证TCP上下行时间公平的ECN标记算法

ECN marking algorithm to achieve time fairness among up/down TCP

在无线局域网络中,针对无线信道的异构性和传输控制协议(transmission control protocol,TCP)闭环拥塞控制的贪婪性,提出了一种基于显式拥塞通告(explicit congestion notification,ECN)标记算法的公平拥塞控制机制(access point congestion control,APCC)。APCC在AP节点结合缓存队列长度和无线信道负载的测量来检测拥塞,依据联合的拥塞测度来实施拥塞控制,通过保证低丢包率和低排队延时得到了高吞吐率;利用ECN显式反馈机制,对通过AP的上行和下行TCP DATA和ACK分组实施ECN标记,实现了上下行公平的双向拥塞控制;同时在多速率信道环境下,依据各流的无线信道速率来调节单流ECN的标记概率,实现不同无线信道速率TCP流之间的时间公平,大大提高了网络的总体效率。

In WLAN,the performance anomaly of wireless channels and the greedy closed loop control nature of TCP congestion control lead to the congestion problem and significant unfair bandwidth distribution among TCP flows.An explicit congestion notification（ECN）-based congestion control scheme called（access point congestion control） APCC is proposed.The main properties of APCC are： Using both wireless channel load and buffer length as congestion indicators,APCC brings low loss rate and low queue delay while keeping high network goodput;APCC achieves the up/down TCP fairness by marking the ECN bit to TCP DATA and ACK packets;and taking into account the wireless channel rate of each TCP flow,APCC sets different ECN marking probability for each flow to guarantee the time fairness of each flow and higher total network goodput.