Abstract: To solve the problem of RTT fairness in satellite networks which is resulted by long round trip delay and dynamic topology，an improved RTT fairness algorithm，the TCP Riff，is presented.It introduces a reference connection RTT，which makes the evolution of congestion window，and then the transmission rate of connection independent of RTT，and gets improved RTT fairness.NS simulation results show that TCP Riff has an evident superiority with respect to TCP standard，in all of the cases examined，which includes throughput，fairness and friendliness.Finally，it is worth noting that TCP Riff does not infringe the end-to-end semantic of TCP and is fully compatible with other promising enhancement.

Key words: Round Trip Time（RTT） unfairness, satellite networks, reference connection

摘要： 为解决卫星网络中由于链路长时延、网络拓扑动态变化等造成的TCP连接RTT不公平性问题，给出了一个卫星网络中RTT不公平性增强方案TCP Riff。TCP Riff中引入了参考连接RTT的概念，通过一个基准RTT，使得异构RTT的TCP连接窗口的增长，继而传输速率的增长独立于连接的RTT，从而获得了很好的RTT公平性。NS仿真实验表明TCP Riff明显地减少对长RTT连接的性能差异，并且，在出现拥塞和链路差错情况下，相对于TCP标准版本具有明显的吞吐量优势，以及良好的公平性和友好性。值得提出的是TCP Riff没有破坏TCP协议端到端的语义，并且与其他TCP增强方案是兼容的。

关键词: 往返时延（RTT）不公平性, 卫星网络, 参考连接