British Telecommunications Public Limited Company

Benjamin P Niven-Jenkins

John R King

Andrew Lord

Paul W Burke

A partitioned network has several subdomains (,) each having a respective access server () and each serving a plurality of end users (). Each access server () is connected to a respective content cache () or a set of such caches (), which stores content and downloads it to end users on request. An alternative routing () may be available between an access server () and a content cache () other than its associated cache (), for use in exceptional circumstances. All the content caches (), are given the same IP address, 'W.X.Y.Z'. Each access server () operates exclusively in a geographic sub-domain, and recognizes the IP address W.X.Y.Z as relating uniquely to its respective associated content cache, () This means that the configuration of each access server () to handle content caching/distribution/streaming can be the same regardless of its location in the network. Any end user () can therefore obtain content from the cache () 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 () is unable to connect to the associated content server (), it is configured to forward traffic to another content cache (), by tunnelling the request to an access server () associated with that second cache. The second access server () recognizes the address W.X.Y.Z as being that of its own associated content server (), rather than the content server () associated with the first access server (), and forwards the request accordingly. The content can then be returned to the address of the requesting user.

Operation of a content distribution network

A wavelength is selected for use in transmitting optical data along a path in an optical network. Wavelengths that are available for use end-to-end along the path are found, the wavelengths that are available on each link attached to each node on the path are found and a wavelength that is available end-to-end and that is more available on the links attached to the nodes is selected.

Wavelength selection

A path is established through an optical communications network. One or more partial paths are evaluated according to a first criterion, and candidate end-to-end paths are then evaluated according to a second criterion. The end-to-end path evaluation disregards candidate end-to-end paths that include partial paths not meeting the first criterion. A path is established by selecting one of the candidate end-to-end paths on the basis of the second criterion.

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Ipswich, United Kingdom

Benjamin P Niven-Jenkins