Performance evaluation of hierarchical routing in ATM networks

The hierarchical routing model was proposed for ATM networks to reduce the amount of storage as well as communication overheads that would result if flat routing is used. This is achieved by having each node store and transmit only a partial set of information about the network status instead of a complete one. However this may result in a degradation of the performance of these networks due to the lack of complete information at each node. In this paper we evaluate the performance of the hierarchical routing model in order to compare it to its flat counterpart. This comparison may be helpful in deciding when to use the hierarchical model and when to use the flat one. The comparison is based on both the savings in overheads and the degradation of performance that would result in case of using hierarchical routing. This comparison is done partly through mathematical treatment and partly through simulation of both models on a well-known network (NSF network). The results of this study show that for small size networks where the overhead is not so critical it is better to use the flat model while in case of large networks the overhead becomes a bottleneck and it would be better to use the hierarchical model