John Heidemann

Assessing Affinity Between Users and CDN Sites

TitleAssessing Affinity Between Users and CDN Sites
Publication TypeConference Paper
Year of Publication2015
AuthorsX. Fan, E. Katz-Bassett, and J. Heidemann
Date Publishedapr
Conference LocationBarcelona, Spain

Large web services employ CDNs to improve user performance. CDNs improve performance by serving users from nearby Front-End (FE) Clusters. They also spread users across Front-End Clusters when one is overloaded or unavailable and others have unused capacity. Our paper is the first to study the dynamics of the user-to-Front-End Cluster mapping for Google and Akamai from a large range of client prefixes. We measure how 32,000 prefixes associate with Front-End Clusters in their CDNs every 15 minutes for more than a month. We study geographic and latency effects of mapping changes, showing that 50–70% of prefixes switch between Front-End Clusters that are very distant from each other (more than 1,000\,km), and that these shifts sometimes (28–40% of the time) result in large latency shifts (100\,ms or more). Most prefixes see large latencies only briefly, but a few (2–5%) see high latency much of the time. We also find that many prefixes are directed to several countries over the course of a month, complicating questions of jurisdiction.