A mathematical programming formulation of optimal cache expiration dates in content networks

One of the fundamental decisions in content networks is how the information about the existing contents is deployed and accessed. In particular, there are two main alternatives, either to publish the information when contents are changed, or to search for the contents when a query is received. Even if some networks only use one of these alternatives, in general it is better to employ a mix of both strategies. This implies evaluating the tradeoff between these alternatives, in order to decide the characteristics of the mix. In this work we develop a simplified model of the costs and restrictions associated with cache expiration dates in a cache node in a content network; these expiration dates regulate the proportion of queries which will be answered on the basis of published information, vs. those which will give rise to additional searches in the network backbone. Based on this model, we present a mathematical programming formulation which can be useful to determine the optimal cache expiration dates in order to maximize the total information discovered, while respecting the operational constraints of the network.