Operation of a content distribution network

摘要

A partitioned network has several subdomains 1, 2, 3, each having a respective access server 10, 20, 30 and each serving a plurality of end users 11, 12; 21, 22; 31, 32. Each access server 10, 20, 30 is connected to a respective content cache 13, 23 or a set of such caches 130, 131, 132, which stores content and downloads it to end users on request. An alternative routing 19, 29 may be available between an access server 10 and a content cache 23 other than its associated cache 13, for use in exceptional circumstances. All the content caches 13, 23, are given the same IP address, "W.X.Y.Z". Each access server 10, 20, 30 operates exclusively in a geographic sub-domain, and recognises the IP address W.X.Y.Z as relating uniquely to its respective associated content cache 13, (23, 23) This means that the configuration of each access server 10, 20, 30 to handle content caching/distribution/streaming can be the same regardless of its location in the network. Any end user 10 can therefore obtain content from the cache 13 which is topologically closest, using the common IP address W.X.Y.Z . No address translation or mapping is required to route requests to the correct local content server. If the access server 10 is unable to connect to the associated content server 13, it is configured to forward traffic to another content cache 23, by tunnelling the request to an access server 20 associated with that second cache. The second access server 20 recognises the address W.X.Y.Z as being that of its own associated content server 23, rather than the content server 13 associated with the first access server 10, and forwards the request accordingly. The content can then be returned to the address of the requesting user.