Unified approach for analyzing persistent, non-persistent and ON-OFF TCP sessions with RED control and exogenous traffic

Abstract

We first look at a router with multiple TCP and UDP connections. The UDP stream has pre-emptive resume or non pre-emptive priority over the TCP connections. The UDP stream is modeled as a Markov modulated Poisson process and can actually be a superposition of several UDP streams. The packet lengths of different streams can be iid with general distributions. We obtain the stability and expressions for various performance parameters: the throughput of various TCP streams with different propagation delays and other parameters, their mean sojourn times and the mean sojourn time of the UDP stream. Next we obtain all the above results when the router deploys the RED congestion control algorithm. Our approximations are verified through extensive simulation results. We further investigate the case when the TCP flows pass through a tandem of routers with each router having exogenous cross traffic. We also look at the case when the router deploys class based queuing (CBQ). Both of the above systems we study for the case when the router has infinite or very large size buffer and also for the case when the router deploys the RED congestion control algorithm. We next consider the situation when a large number (100’s) of TCP connections share the router with exogenous UDP traffic. We obtain the bandwidth sharing and hence the mean file download times of each of these TCP connections, when all of them are having different propagation delay, packet size and max window size parameters. In this model the TCP flows can be of two types either Persistent ON-OFF or Non-Persistent where a TCP connection arrives, sends a finite size file and then leaves. We have modeled the TCP slow start phase. We also obtain the mean sojourn times of the UDP packets. Here also we study the system for the infinite buffer case and when the RED control is deployed. Our approximations are verified via extensive simulations.