Modeling TCP Throughput: A Simple Model and its Empirical Validation Jitendra Padhye, Victor Firoiu, Don Towsley, Jim Kurose ABSTRACT In this paper we develop a simple analytic characterization of the steady state throughput as a function of loss rate and round trip time for a bulk transfer TCP flow, i.e., a flow with an unlimited amount of data to send. Unlike the models in [5, 6, 9], our model captures not only the behavior of TCP's fast retransmit mechanism (which is also considered in [5, 6, 9]) but also the effect of TCP's timeout mechanism on throughput. Our measurements suggest that this latter behavior is important from a modeling perspective, as almost all of our TCP traces contained more timeout events than fast retransmit events. Our measurements demonstrate that our model is able to more accurately predict TCP throughput and is accurate over a wider range of loss rates.