Workshop on interdisciplinary systems approach in performance
evaluation and design of computer & communication systems

In this paper, we propose TCP Symbiosis, which has a robust, self-adaptive and scalable congestion control mechanism for TCP. Our method is quite different from existing approaches. We change the window size of a TCP connection according to the information of the physical and available bandwidths of the end-to-end network path. The bandwidth information is obtained by an inline network measurement technique we have previously developed. Using the bandwidth information we can resolve the inherent problems in existing AIMD/MIMDbased algorithms such as periodic packet loss and unfairness caused by the difference in RTT. We borrowed algorithms from biophysics to update the window size: the logistic growth model and the Lotka-Volterra competition model. This is because these models describe changes in the population of species dependently on the living environment. The population of a species can be viewed as the window size of a TCP connection and the living environment as bandwidth of the bottleneck link. The greatest advantage of using these models is that we can refer previous discussions and results for various characteristics of the mathematical models, including scalability, convergence, fairness and stability in these models. Through mathematical analysis and extensive simulation experiments, we compare the proposed mechanism with traditional TCP Reno, HighSpeed TCP, Scalable TCP and FAST TCP, and exhibit its effectiveness in terms of scalability to the network bandwidth and delay, convergence time, fairness among competing connections, and stability.