Analysis of Scalable TCP

Scalable TCP [2] is a proposition for a new TCP where both the increase and the decrease rate of the window size are multiplicative. It has been recently proposed in order to improve performance in high speed networks. In this paper, we present a mathematical analysis of such multiplicative increase multiplicative decrease protocols in the presence of random losses. These are typical to wireless networks but can also model losses in wireline networks with very high bandwidth delay product. Our approach is based on showing that the logarithm of the window size evolution has the same behaviour as the workload process in a standard G/G/1 queue. The Laplace-Stieltjes transform of the equivalent queue is shown to provide directly the throughput of Scalable TCP as well as the higher moments of the window size. We validate our findings using ns-2 simulations.