Load sharing in Call Server clusters

A Call Server in a telephone switch is responsible for connecting the calling and called subscribers. A cluster of Call Servers that serves the subscribers in a large geographical area can provide geographic redundancy, scalability, reduced operational cost, fault tolerance and load sharing. This paper focuses on load sharing in Call Server clusters, particularly on strategies for redirecting new calls from one Call Server to the other. It investigates relative performances of static and adaptive approaches for effectively handling the load spike’s occurring on the system. A detailed simulation model is developed using the OPNET tool. The model is used to study the performance of the Call Server clusters under different load conditions. A comparison of the performances of different redirection policies is presented. The impact of different load sharing thresholds on performance is analyzed and various insights gained into system behavior and performance are described.