Self-Similarity in World Wide Web Tra c: Evidence and Possible Causes

Recently the notion of self-similarity has been shown to apply to wide-area and local-area network tra c. In this paper we show evidence that the subset of network tra c that is due to World Wide Web transfers can show characteristics that are consistent with self-similarity, and we present a hypothesized explanation for that self-similarity. Using a set of traces of actual user executions of NCSA Mosaic, we examine the dependence structure of WWW tra c. First, we show evidence that WWW tra c exhibits behavior that is consistent with self-similar tra c models. Then we show that the self-similarity in such tra c can be explained based on the underlying distributions of WWW document sizes, the e ects of caching and user preference in le transfer, the e ect of user \think time," and the superimposition of many such transfers in a local area network. To do this we rely on empirically measured distributions both from client traces and from data independently collected at WWW servers.