Abstract
Congestion control of TCP protocol will reduce the size of congestion window to insure data transmission and reduce the degree of network congestion when a packet loss event that is regarded as a symbolic event of network congestion occurs. This method can be very effective in the low BER link, but it causes a sharp reduction of data transmission performance of TCP in a high BER link such as wireless link, because the reasons that cause packet loss in wireless link include not only network congestion, but also single attenuation, electromagnetic interference, abrupt change of routing, quick move of network terminal and so on. Network congestion is a gradual process, the change of degree of network congestion is relatively slow, but the packet loss event caused by other reasons is sudden and can resume quickly. When packet loss occurs, we can avoid the unnecessary reduction of congestion window size by tracing and analyzing the change trend of RTT and determining the real reason of packet loss, so that the data transmission performance of TCP is improved dramatically.