Performance evaluation of ATM shortcut connections in overlaid IP/ATM networks

In this paper we present methods to evaluate the benefit of using direct ATM connections (shortcuts) between IP nodes in IP over ATM networks, and we identify the combinations of IP and ATM network topologies where ATM shortcut benefits are likely to be high. We model an IP/ATM network with and without ATM shortcuts as two loss networks. We propose a metric for network performance comparison, the network load ratio, that gives the ratio of the number of flows accepted by two networks at the same network blocking probability. We derive an estimator of this metric, the asymptotic load ratio, that has low computational complexity. This estimator forms the basis of a methodology for network performance comparison. We use this method in simulation experiments using random networks. These experiments indicate that in many cases the utilization of an IP/ATM network increases proportionally to the decrease in the average path length when ATM shortcuts are used. We have also found that there is almost no correlation between the increase in network utilization (when using ATM shortcuts) and the IP to ATM node ratio.