Load Balancing Control of Web-server Clusters: N-Tanks Model and a CTCT Method

With an increasing of the traffic on Internet, a Web-server usually overloads during a heavy-request period. Web-server cluster architectures have been widely employed to provide high-efficiency Internet services. This paper is concerned with load balancing control of Web-server clusters. A Web-server is modelled as a tank with an inflow and an outflow, and hence a Web-server cluster is modelled as a multiple-tanks system with certain inflow constraint. A control technique, called continuous token control technique (CTCT), which adopts conventional PID approach is proposed to address the issue of the traffic balancing on the Web-server clusters. The principle of the proposed approach is explained and demonstrated. Simulation results show that the proposed CTCT technique is effective and scalable.