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In this paper, we present a novel technique for the problem of designing a Content Distribution Network (CDN), which is a technology used to efficiently distribute electronic content throughout an existing IP network. Our design proposal consists of jointly deciding on (i) the number and placement of proxy servers on a given set of potential nodes, (ii) replicating content on the proxy servers, and (iii) routing the requests for the content to a suitable proxy server such that the total cost of distribution is minimized. We model the problem using a nonlinear integer programming formulation. The novelty of the proposed formulation lies in simultaneously addressing three interdependent problems in this context as well as explicitly representing the distribution structure of a CDN through the objective function. We offer a linearization for the model, develop an exact solution procedure based on Benders' decomposition and also utilize a variant of this procedure to accelerate the algorithm. In addition, we provide a fast and efficient heuristic that can be used to obtain near-optimal solutions to the problem. Finally, the paper concludes with computational results showing the performance of the decomposition procedure and the heuristic algorithm on randomly generated Internet topologies. © 2006 Elsevier Ltd. All rights reserved

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We propose a simple and a quite efficient separation procedure to identify cover inequalities for the multidimensional knapsack problem. It is based on the solution of a conventional integer programming model. Solving this kind of integer programs is usually considered expensive and the proposed method may have been overlooked because of this assumption. The results of our experiments with a small set of randomly generated problems and problems taken from the literature indicate that the method may be a reasonable alternative to the one currently in use.