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Here we present the results of a study to determine the effects of link failures on network performance. The network studied is a virtual circuit based packet switched wide area network. A generic queueing framework is developed to study the effect of failures, and the subsequent trafic restoration, on network performance. In general, the congestion resulting after a failure is a transient phenomenon. Hence a numerical methods based nonstationary queueing analysis is conducted in order to quantify the effects of failures in terms of the transient behavior of queue lengths and packet loss probabilities. A bounding relationship is developed whereby a network node can determine whether or not congestion will occur as the result of trafic restoration after a failure. Modeling the effects of failuresConsider the arbitrary packet switched wide area network shown in Figure 1. We assume that the network uses virtual circuit service to transport packets and source node routing of the virtual circuits. In source node routing each network node maintains a database of the network topology and determines the route through the network for all virtual circuits originating at the node.The impact of a link or node failure on the network performance will depend on the complex interaction of several factors, some of which are the location of the 9a.2.1

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