Sensitivity Analysis of the Load on an Ethernet Network

In this paper a sensitivity analysis of the load on an ethernet network is presented. Aim is to determine which parameters that characterize the workload have an influence on the performance of an ethernet segment and to get an idea about the magnitude of this influence. The performance ofthe network is indicated by the wai ti ng ti me and the access del ay. The performance is measured using a simulation model. The simulation model is a very accurate description of a real ethernet implementation and has been validated with the results of real life measurements (Van Oorschot and Dekkers [9], Thio [6]). The main advantages of simulation are the detailed infonnation that can be obtained and the absence of expensive laboratory measurements. The importance of this sensitivity analysis is to validate future modelling assumptions and to get a better insight in the behaviour of the ethernet protocol. From the research it can be concluded that the performance is sensitive not just to the load of the ethernet, but also to the distribution of the interal1"iva1 times, the possibility of batch arrivals and the fraction of traffic arriving in large messages of a number of packets. Therefore existing models (e.g. Tobagi and Hunt [11], Lam [5], Bertsekas and Gallager [2]) only yield a rough performance estimation of a real ethernet segment, because they assume Poisson arrivals and do not consider batches. 1 The investigations were supported (in pUlt) by the Foundation for Computer Science in the Netherlands (SIGN) with financial aid from the Netherlands Organization for the Advancement of Scientific Research (NWO). Sensitivity Analysis of the Load on an Ethernet Network 1