Improvements Of The TCP Performane Over Mobile IP

With the development of network and communications technology, more and more people desire for jumping the traces of restriction of area and space , and accessing the Internet whenever and wherever. Nevertheless, the traditional TCP/IP protocols have all kinds of restrictions deriving from themselves, and can not accomplish the incessant communications during moving. Thus, the Internet Engineering Task Force (IETF) established the Mobile IP for the mobile IP protocol.For that the Mobile IP has the idiographic application environments and the design goals, the TCP performance are inevitably influenced when applying the TCP protocols to the Mobile IP. In the practical application, what influences the TCP performance mainly lies in two aspects: one is the typical environment of using the Mobile IP, namely in the hybrid network consisting of wire- and wireless network. Because the congestion control mechanism of the TCP can not adapt to the situation that high rate of error code leads to the loss of packets of the wireless link in the wireless network, the usage efficiency of the channel will be cut down if directly adopting the congestion control mechanism of the TCP. In addition, in the process of smoothly switch between the mobile nodes, the interruption of the link inevitably occurs and there is potential great difference of the transmission delay between the new link and the old link, which would make the TCP performance dither greatly and then influence the usage efficiency of the channel. All the existing schemes, which are used to ameliorate the TCP performance in the application of the Mobile IP, do not solve the problems of the TCP performance thoroughly.For the sake of solving the above problems from the two aspects, the improvements are implemented as the following two aspects. Firstly, through setting the historical windows of the data package by taking use of the foreign agent, every data package takes the state information of several anterior data packages, which facilitates that the both communicat- ing sides can differentiate the real reason leading to the loss of package. Then different control measures of TCP are taken according to different reasons leading to loss of package. Secondly, The delay in the switch between the mobile nodes is calculated and the time for sending the data packages in the buffer is estimated by taking use of the foreign agent, then the communications opposite is informed and takes corresponding control measure of TCP according to the magnitude of delay. It turns out that with the improvements in the two aspects, the two key problems influencing the TCP performance in the Mobile IP can be solved and the TCP performance in practical application can be enhanced.