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Web++ is a prototype system that supports user transparent wide area replication of resources in order to improve the response time and reliability of the HTTP service. Our architecture is based on smart clients, and can be dynamically downloaded as mobile code into a user's application, presents a number of advantages. Clients keep track of the average HTTP latency that they experience from various servers and use that information in order to make to choose the replica of a resource that is expected to deliver the best response time for them. The clients also provide feedback on the observed request latencies to the servers, which allows helps the servers to determine which resources should be replicated and what would be the best locations for the replicas. We describe in this paper a distributed server-initiated approach for resource replication in which all servers can decide autonomously whether to replicate resources and the locations where the replicas should be allocated. In addition to the novel use of smart clients, our algorithm also avoids keeping track of complex network topologies by using the concept of logical segments. We present the results of experiments that show that our algorithm for resource allocation scale well with respect to the number of servers and the number of replicated resources.
Date of Conference: 16-18 April 2003