FAST TCP performance under perturbation imposed queueing delay in equilibrium

In this paper, we investigate the performance of FAST TCP under perturbation imposed queueing delay in equilibrium in dumbbell networks. We derive the transfer functions of the delay perturbation to the FAST TCP congestion window, queueing delay, and throughput. By using the transfer functions, the effects of impulse, step, and ramp delay perturbation on the congestion window, queueing delay, and throughput are theoretically analyzed. It is shown by the analysis that ramp delay perturbation makes FAST TCP unstable and step delay perturbation leads to constant errors, while impulse delay perturbation does not influence FAST TCP stability. The throughput of FAST TCP flows under different types of delay perturbations are simulated by ns-2. The simulations agree with our analytical results.