Analysis of scalable TCP congestion control algorithm

In recent years, several more aggressive versions of TCP have been proposed which leave the Additive Increase Multiplicative Decrease (AIMD) paradigm. The motivation is to adapt TCP to networks with very large bandwidth delay products. In this paper, we study the scalable TCP (STCP) which is designed to be a Multiplicative Increase Multiplicative Decrease (MIMD) protocol. We analyze how it shares a bottleneck link with other CBR flows. We identify conditions under which the time varying queueing delay transforms the whole multiplicative increase dynamics of the window size into an additive increase dynamics, which implies that window evolution of STCP behaves as an AIMD protocol. In addition, we analyze and derive expressions for the case of very small buffer. Finally, we validate our results using ns-2 simulations.