In early literature about the performance of telecommunication systems, traf®c was generally modeled as memoryless Poisson streams of packets. In these models the packet arrival processes show no time interdependence. Recent measurements on Web traf®c show that this hypothesis is wrong and that Web traf®c actually experiences what we now call long-term dependence. Long-term dependence is interesting not only because it contradicts Poisson's law, but also because it signi®cantly impacts the perfo