Self-similarity in World Wide Web Traac 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 examine the mechanisms that give rise to the self similarity of network tra c We present a hypothesized explanation for the possible self similarity of tra c by using a particular sub set of wide area tra c tra c due to the World Wide Web WWW Using an extensive set of traces of actual user exe cutions of NCSA Mosaic re ecting over half a million requests for WWW documents we examine the dependence structure of WWW tra c While our measurements are not conclusive 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 empir ically measured distributions both from our traces and from data independently collected at over thirty WWW sites