A Multi-level TCP Model with Heterogeneous RTTs

This paper studies TCP performance focusing on the mean flow transfer delay and the average number of concurrent flows in the system. This is done for a dynamic population of users, rather than a static number of permanent flows. The modeling approach relies on using idealized processor sharing models as a starting point and modifying their properties to take into account some of TCP’s non-ideal behavior. To this end, a model is derived that incorporates the effect of packet losses and RTTs on the goodput, as well as limited sending rates. Also, the unequal sharing of bandwidth between flows with different RTTs can be treated. The delay estimates take into account the initial slow start. Extensive ns2 simulations are used to verify the accuracy of the models.