In this project, we present the design and implementation of virtual network testbeds for studying routing changes. A virtual network testbed is a computer network that is completely created in software, while routing changes directly impact on the reliability and the reachability information of the network. We used testbeds to emulate a small and a large-scale network on a single Linux machine. These emulated networks allow the study of network behavior and operations which are examined using two routing protocols: Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). We implemented a fifteen-node network to study RIP, and a model of the GÈANT network to examine OSPF in virtual network testbeds. Each testbed represents an autonomous system (AS) or an intra-domain environment. Therefore, these environments provided us with the opportunities to evaluate routing changes in an AS. We used the testbeds to compare the routing of the original network with the new routing of the missing links and routers to see what changes occur. The GÈANT network is the large-scale network used for investigations in this project. We then used our emulation results of the large-scale network to compare with the simulation work for the same network topology-the GÈANT network, and confirmed that our emulation studies also identified important links and routers in the same network. --P.ii.
