适用于异构网络的改进TCP协议研究

Research on Improving the Performance of TCP for Heterogeneous Networks

在有线网络中,网络丢包主要是网络拥塞造成的,而传统的TCP协议主要是针对有线网络设计的。对于无线网络,链路错误的随机丢包成为其主要的丢包,传统的TCP已不再适用。为了使TCP适用于有线-无线的异构网络中,提出一种改进的TCP协议(命名为TCP-Ackflag)。此协议通过接收端判断分组数据的相对延迟趋势来判断网络拥塞情况,并在接收端反馈给发送端的ACK包中定义一个拥塞标志位。接收端在接收ACK包中,记录这个拥塞标志位。为了使网络能达到最大吞吐量,发送端只有在发现产生网络丢包现象后再立即对记录的拥塞标志位的值进行检测,通过检测到的拥塞标志位的值来判断网络拥塞情况,最终决定是进入网络拥塞处理过程还是简单地快速重传过程,从而保证了有线-无线异构网络的传输性能。仿真结果表明,此方案对网络拥塞判断准确性和灵敏性都有极大提高,并在此基础上保证了网络传输性能。

In wired network,the packet loss is caused by network congestion.TCP protocol was designed for wired network.But it isn＇t adapted to the wired-wireless networks anymore because packet loss is mainly caused by link errors in wireless networks.So it proposed a new protocol（named TCP-Ackflag） based on TCP.It judges network congestion according to trend of relative time delay in receiver.Then the receiver sends an ACK with network congestion flag bit（NCF） to the sender.For the maximum throughput,the sender checks the NCF in ACK which is received recently when it has found the packet loss.It will deal with network congestion or fast retransmit according to network congestion flag bit in ACK.The simulation results show the accuracy and sensitivity in this programs on the network congestion to determine are greatly improved,and on this basis to ensure the network transmission performance.