Variations in cache behavior.

HTTP cache servers reduce network traffic by storing popular files nearer to the client and have been implemented worldwide. Their reported performance on key metrics such as hit rate varies greatly. In order to optimise the design of the cache network this variation needs to be understood. The variation in hit rate across a number of caches is investigated and is shown to be partly stochastic (i.e caused by insufficient sample size) and partly fractal (i.e deterministic in origin)