An optimal method for coordinated en-route web object caching

Web caching is an important technology for saving network bandwidth, alleviating server load, and reducing the response time experienced by users. In this paper, we consider the object caching problem of determining the optimal number of copies of an object to be placed among en-route caches on the access path from the user to the content server and their locations such that the overall net cost saving is maximized. We propose an object caching model for the case that the network topology is a tree. The existing method can be viewed as a special case of ours since it considers only linear topology. We formulate our problem as an optimization problem and the optimal placement is obtained by applying our dynamic programming-based algorithm. We also present some analysis of our algorithm, which shows that our solution is globally optimal. Finally, we describe some numerical experiments to show how optimal placement can be determined by our algorithm.