document: Track globally , deliver locally : improving content delivery networks by tracking geographic social cascades Providers such as YouTube offer easy access to multimedia content to millions , generating high bandwidth and storage demand on the Content Delivery Networks they rely upon . More and more , the diffusion of this content happens on online social networks such as Facebook and Twitter , where social cascades can be observed when users increasingly repost links they have received from others . In this paper we describe how geographic information extracted from social cascades can be exploited to improve caching of multimedia files in a Content Delivery Network . We take advantage of the fact that social cascades can propagate in a geographically limited area to discern whether an item is spreading locally or globally . This informs cache replacement policies , which utilize this information to ensure that content relevant to a cascade is kept close to the users who may be interested in it . We validate our approach by using a novel dataset which combines social interaction data with geographic information : we track social cascades of YouTube links over Twitter and build a proof-of-concept geographic model of a realistic distributed Content Delivery Network . Our performance evaluation shows that we are able to improve cache hits with respect to cache policies without geographic and social information .
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