Performance evaluation of TCP over optical links

Future applications will need steady transfer rates in the order of gigabits or even terabits per second in order to exchange exabytes of data in a reasonable amount of time and support collaborative scientific work. Although it is expected that next generation optical networks, computing and storage technologies will support this scenario, it has been shown that communications protocols, and in particular the widely used TCP protocol, will become the bottleneck. In this paper we present a performance evaluation of TCP Tahoe, Reno, New Reno, SACK, Vegas, Westwood and HighSpeed TCP over optical channels. We compared them in the same environment and found that the window-based mechanism of current TCP implementations is not suitable to achieve high link utilization, and that other congestion control mechanisms, such as the ones utilized by Vegas and Westwood, are more appropriate and provide better performance. In addition, we propose a simple modification to TCP Vegas that further improves its performance.