Content delivery has seen dramatic growth over the last decade, with large publishers typically distributing the load among geographically dispersed edge-servers to improve end-user performance. A massive increase in demand for these services has fostered many centralized content delivery networks or CDNs, as we know them today.
CDNs have been around since the 90's. They have grown in size and added several features, but the underlying mechanism has remained essentially the same. CDN vendors operate hundreds of physical servers (edges) across the world that cache content and direct traffic to the nearest physical server.
Media Network: A Peer-to-Peer Content Delivery Network