Caching Strategy and Service Policy Optimization in a Cache-Satellite Distribution Service

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This paper introduces the caching strategy and service policy optimization problem in a cache-satellite distribution service and formulates it as a mathematical optimization problem. A number of system performances like hit rate, cache disk space, bandwidth gain, bandwidth requirements for the satellite channel and latency experienced by the clients were modeled into a mathematical formulation. To show how the optimal caching and service policy responds to the system parameter changes, computational experiments were performed on a hypothetical market having forty ISPs and one billion Web documents. It was found that the correlation between document size and popularity is most influential and the concentration of popularity appeared to be the main factor determining the sensitivity of the optimal caching levels and the corresponding system performances like hit rate and byte hit rate. The achieved hit rate ranged between 64 and 74% with the corresponding caching levels of 25 to 40%. Based on these findings, the importance of caching strategy and service policy optimization was discussed and a number of further research issues were suggested.