The Implementation And Experimental Study Of A Self-tune Congestion Control Protocol PI Rate Controller

In the past twenty years, Internet has developed with fast speed, and a great variety of applications upon the Internet, like electronic business and network multimedia, emerge as the times require. With the increasing traffic of network, congestion control turns out to be the most important issue in the research of network. The existed congestion control algorithms are able to alleviate congestion to some aspect, but still there's no perfect solution.The congestion control algorithm that TCP adopts is not smooth enough, and moreover, because of its inherent limitation, TCP is not suitable for network with high delay, since it could not make full use of the bandwidth. In order to solve these problems, Self-tune Proportional-Integral Rate Control Protocol (PI protocol) is proposed according to the modern control theory to achieve high link utilization, low queuing delay, small packets loss rate and excellent fairness by introducing congestion controller to intermediate nodes.In this paper, we have looked into the theory behind the development of PI protocol, and guided by system control model and theoretic formulas, we simplified the expressions following strict mathematical theory, so that they would be fitting for the use of programming. We also analyzed other important issues that need to solve before we could implement the protocol in Linux kernel, like how to choose kernel version, how to make use of kernel module, how to design protocol stack layer, how to solve floating point calculation problem in the kernel, how to decide the controlling time and so on. Also, we compared PI protocol with XCP protocol. Then, we built up a test bed after solving the problems, and designed a specific experimental scenario to test the performance of the protocol and to find any problems that exist. The results showed that controlling process of PI protocol was accurate and efficient, with high bandwidth utilization and preferable stability, fairness, convergence and robustness.At the last part of this paper we point out the direction for improving the PI protocol.