FluidSim: A Tool to Simulate Fluid Models of High-Speed Networks Jos´ e Incera a1 , Raymond Marie b , David Ros b and Gerardo Rubino b a ENST Bretagne, 2 rue de la Chˆ ataigneraie, 35512 Cesson-S´ evign´ e Cedex, France 2 b IRISA, Campus de Beaulieu, 35042 Rennes Cedex, France 3 Abstract In this paper we present a tool for the simulation of fluid models of high-speed telecom- munication networks. The aim of such a simulator is to evaluate measures which can not be obtained through standard tools in reasonable time or through analytical approaches. We follow an event-driven approach in which events are associated with rate changes in fluid flows. We show that, under some loose restrictions on the sources, this suffices to ef- ficiently simulate the evolution in time of fairly complex models. Some examples illustrate the utilization of this approach and the gain that can be observed over standard simulation tools. Key words: Discrete-event simulation, Fluid simulation, Fluid traffic models, Performance evaluation, Network simulation 1 Introduction Computer networks continue to evolve, increasing in size and complexity. When we have to analyze some aspect of the behavior of an existing network or to de- sign a new one, the most widely used tool is simulation, both because of its power in representing virtually every possible mechanism and system, and because of its flexibility. The main price to pay is in programming and computation costs: simula- tion programs are usually difficult to develop; besides, they may need large amounts of resources in time and sometimes also in space. The best alternative to simula- tion is to use analytical techniques. In general, they offer the advantages of being several orders of magnitude less expensive to apply and, moreover, of frequently 1 Partially financed by CONACyT, M´ exico and by CROUS, France. 2 E-mail: Jose.Incera@enst-bretagne.fr 3 E-mail: marie, dros, rubino @irisa.fr Preprint submitted to Elsevier Preprint 7 November 2000