Snapshot Simulation of Internet Traffic: queueing of fixed-rate flows

Simulations involving processes at very different time scales can be so slow to converge that starting in one state and waiting for a representative sample of the state space to be explored is not feasible. Under these circumstances we need to explore a representative range of starting states for a collection of simulations in order to obtain valid results in a reasonable time. Internet traffic is an example of this situation. This is due to the fact that it is made up of clearly identifiable flows and a significant proportion of overall bytes occur in long-lived flows, whose overall duration will in many cases be longer than can be simulated. In this paper we develop a method which constructs a “randomly selected state” of Internet traffic from scratch. This paper explores a technique previously applied to fair queueing and optimized queueing of bottle-necked flows, this time studying the buffering of an aggregation of flows with a common fixed rate (due to limitations of the source or elsewhere along the path of the flow). Direct and importance sampled simulations are validated and compared to an analytical model of the same system.