Distributed packet rewriting and its application to scalable server architectures

To construct high performance Web servers, system builders are increasingly turning to distributed designs. An important challenge that arises in such designs is the need to direct incoming connections to individual hosts. Previous methods for connection routing (layer 4 switching) have employed a centralized node to handle all incoming requests. In contrast, we propose a distributed approach, called distributed packet rewriting (DPR), in which all hosts of the distributed system participate in connection routing. DPR promises better scalability and fault-tolerance than the current practice of using centralized special-purpose connection routers. We describe the implementation of four variants of DPR and compare their performance. We show that DPR provides performance comparable to centralized alternatives, measured in terms of throughput and delay. Also, we show that DPR enhances the scalability of Web server clusters by eliminating the performance bottleneck exhibited when centralized connection routing techniques are utilized.