Modeling TCP Window Evolution Process with both Discrete and Fluid Models

Fluid model and discrete-packet model are two approaches to model TCP, where different loss processes are used in different models. In this paper, we present both a discrete SMP model and a fluid model to model the TCP window evolution process. Loss process is I.I.D. in the SMP model, and is a poisson process with window size dependent arrival rate in the fluid model. Analysis shows that the discrete SMP model approaches to the fluid model as 0 p → , which sets up a connection between discrete-packet models and fluid models. It allows us to understand the relationship between several existing fluid models and discrete-packet models, especially the relationship between different loss processes. In addition, we analyze the impact of maximum window size limitation ( lim W ) to the throughput, and a simple relation between the lim W and average window size ( aver W ) is obtained. Finally, a set of experiment is conducted over the real Internet and in simulation to validate the model. Keywords—TCP window evolution process, SMP, Fluid