Multi - area intra - domain routing

In this work we study the OSPF protocol focussing our attention on the multi-area architecture. The target of the work is to model the multi-area OSPF and to analyze the complexity it introduces in the intra-domain routing. To make this we propose a model of the OSPF protocol. The aims of the model is to discover the routing choices performed by the routers without reproducing the exchange of information between the routers. The model was implemented in the C-BGP simulator. The prototype is used to validate the model and to study a special situation that we call forwarding deflection. This consists in an inconsistency between the routing plane and the forwarding plane. The cause of the deflection are explained and the condition for it to arise are defined. An algorithm to detect deflection is proposed and implemented in C-BGP. The result of this work consists in the OSPF model and in the deflection detection algorithm implemented in C-BGP. The first can be used in C-BGP to have most realistic models of real networks when these use a multi-area OSPF. The algorithm that detects deflection can be used to discover if deflection arises in a real network. Above all the work allows to show how the complexity introduced with the multiarea OSPF should be induced the operators to use it with care.