Hierarchical networks and the LSA N-squared problem in OSPF routing

With N routers in a network running the OSPF routing protocol a network topol ogy update can generate on the order of N LSA packets This phenomenon known as the LSA N Squared Problem severely degrades network performance and scalability Hierarchical OSPF net work architectures have been proposed to reduce the number of LSAs that are gen erated by a network topology update We show that equal size areas minimize the number of LSAs Then we derive the opti mal number of areas and the size of areas to create the network producing the min imal number of LSAs Finally we show that the optimal network architecture re duces the number of LSAs from O N to O p N N