Content delivery networks (CDNs) have become a crucial part of the modern Web infrastructure. This paper studies the performance of the leading content delivery provider – Akamai. It measures the performance of the current Akamai platform and considers a key architectural question faced by both CDN designers and their prospective customers: whether the co-location approach to CDN platforms adopted by Akamai, which tries to deploy servers in numerous Internet locations, brings inherent performance benefits over a more consolidated data center approach pursued by other influential CDNs such as Limelight. We believe the methodology we developed for this study will be useful for other researchers in the CDN arena. Categories and Subject Descriptors C.2.1 [COMPUTER-COMMUNICATION NETWORKS]: Network Architecture and Design General Terms Measurement, Performance, Experimentation Keywords Content Delivery Networks, Akamai, CDN Performance