Caching schemes for distributed video services

In an on-demand video system, the repository servers storing all the video contents generally have limited streaming capacities and may not be co-located with the users. To achieve higher user capacity and lower network transmission cost, the distributed servers architecture can be used. In such a system, multiple local servers are placed close to the user pools and, according to their local demands, the servers dynamically cache the contents streamed from the repository. We study in this paper a number of caching schemes by considering whether the local servers can exchange their cached contents among themselves or not. All the caching schemes keep a sliding window worth of data for each video being displayed; hence a video can be partially stored. We study the trade-off between the storage capacity required and the network channel used in each scheme, and address how the system cost can be minimised by appropriately sizing the window. We also show the cost advantage in using such a system over a system of request batching and multicasting in providing distributed video services.