Load balancing techniques for scalable web servers

Scalable web servers can be built using a Network of Workstations (NOW) where server capacity can be added by adding new workstations as the workload increases. The task of load balancing Hyper Text Transfer Protocol (HTTP) traffic to scalable web servers is the topic of this paper. We present a classification framework for scalable web servers, and present simulations of a clustered web server. The cluster communication is modeled using a detailed, verified model of TCP/IP processing over Asynchronous Transfer Mode (ATM). The simulator is a trace driven discrete event simulator, and the traces are obtained from the proxy server of a large Internet Service Provider (ISP) in Norway. Various load balancing schemes are simulated for the prototype using remapping in the network and compared with the Rotaing Nameserver approach. We show that the Round Robin load balancing policy implemented in a modified router gives better average response time and better load balancing than the Rotating Nameserver method used in current scalable web servers.