Facility Location to Maximize Throughput: Networks of Caches and Radiology Archives

Jeff Diamond, TRLabs

Abstract

We consider two similar facility location problems. The first problem involves the placement and sizing of Web caches within a regional Internet service provider network, and the second involves the placement and sizing of archives for digital radiological images amongst hospitals in a metropolitan area. We assume a model for the way in which bandwidth is shared within the network, leading to file transfer times which depend only on overall loads within the network and not on the detailed characterization of arrival processes. We make use of an upper and lower bound for performance under these conditions to construct an objective function for a non-linear programming problem which minimizes the mean time to transmit a file through the network. We solve the optimization problems and investigate the properties of the solution under various capacity constraints on the overall cache or archive capacity. The optimization produces candidate solutions which are investigated through simulation.