Tinnakornsrisuphap, PeerapolLa, Richard J.We introduce a stochastic model of a bottleneck ECN/RED gateway under a large number of heterogeneous TCP flows, ie flows with diverse round-trips and session dynamics. We investigate the asymptotic behavior of the system and show that as the number of flows becomes large, the buffer dynamics and aggregate traffic simplify and can be accurately described by simple stochastic recursions independent of the number of flows, resulting in a scalable model. Based on the central limit theorem results presented in the paper we analyze the sources of fluctuations in queue size and describe the relationship between the packet marking function and variance of queue size.en-USGlobal Communication SystemsTechnical Report