A completely distributed architecture for cluster-based Web servers

While content-aware distribution policies getting more popular in cluster-based Web systems, they make the dispatching node a bottleneck. To achieve scalable server performance, we present a completely distributed architecture named CODA. In CODA, we employ both layer-4 and layer-7 Web switching techniques. While the front-end layer-4 switch distributes the client requests among the server nodes using some simple dispatching algorithm, the server nodes may forward the incoming request to another server node according to some content-aware policy. By eliminating the centralized dispatcher, CODA affords better scalability and fault tolerance. Moreover, we have implemented this architecture on the basis of Linux IP stack and evaluated its performance with trace-based workloads. Our performance results show it can achieve favorable throughput compared to existing architectures.