Study of oscillations in admission control algorithm for Web servers

Abstract

The work of this thesis is oriented towards solving the problem of system performance oscillations. We first establish the relationship between the number of users in the system and the average response time. Then we study a theoretical model of the oscillation of the number of users in the system. Then we propose a probabilistic approach to admission control where the probability of rejecting a new user increases as the load increases. Using the theoretical model, we prove that with a probabilistic approach, the oscillations will normally be suppressed, and the number of users in the system reaches a stable point. We also test the effect of different probability functions and the impact of different inter-observation time intervals on the oscillation by careful simulation experiment. Finally, the probabilistic approach is used to provide differentiated classes of service to different user groups. (Abstract shortened by UMI.)