Performance of Competing High-Speed TCP Flows

The goal of recent high-speed TCP implementations is to allow scientists who have access to new high-speed networks to efficiently transfer large datasets to their remote colleagues. As of yet, there is no standard high-speed TCP. Because of this, scientists using one high-speed protocol may find themselves sharing a link with scientists using a different high-speed protocol. Previous work has evaluated such inter-protocol performance, but only with both flows starting at the same time – an unlikely situation. We perform an evaluation study using ns-2 to investigate the performance of competing high-speed TCP flows where one flow enters a network in which another high-speed flow has already reached its maximum data rate. The fairest result would be for the existing flow to cede half of its bandwidth to the new flow in order to allow both flows to evenly share the link. Our results show that in most cases this does not happen, but rather one high-speed flow dominates the other. Surprisingly, it is not always the existing flow that dominates.