Content Distribution Network

Definition: Content Distribution Network is designed to minimize the network delays when viewing or downloading a multimedia content over the network.

The HTTP client server model does not scale well as the number of clients and the network bandwidth utilization increase. The server is a choke point, and a single point of failure. Adding redundancy and load balancing can help, but this does not deal with overall network load. Content Distribution Networks (CDN) are designed to minimize the delay that the end user experiences when requesting to view or download content such as HTML pages, images, data files, and streaming media. CDNs achieve this goal by deploying and managing a network of edge caches (or proxy caches ) which maintain content replicas that emanate from an origin server . These edge caches are closer to the end user in terms of lower response latency (e.g. smaller number of router hops, higher bandwidth connections) as shown in Figure 1. Algorithms for cache management are employed to optimize resource utilization based on user content consumption patterns. CDNs may also support content management features such as content preloading, prioritization, publication and expiration dates, and digital rights management. Many other CDN architectures are possible including the use of multicast distribution and peer-to-peer caching.