Presenting a New Method, Using Topology Virtualization for Stabilizing Flow Tables in SDWN

Software Defined Networks split the data plane from the control plane. They can be used in wireless networks and will bring flexibility, less interference, simple management, less energy consumption and load balancing. They can also improve service quality, handover and mobility between different service providers. In previous methods, when link states were changed the controller deleted the stored topology and the tables in switches and updated them. Therefore, the controller should not only build the topology, but also execute the routing algorithms and install the routes in switch tables again. This may not cause any problems in wired networks, since link failure may not happen too often, but in wireless networks this happens frequently. In this paper the problems of (1) dynamic topology, (2) removing the whole flow table due to topology changes, and (3) time consuming routing algorithms are addressed. In the proposed method, after building a virtual topology with virtual node coordinates, the controller executes a heuristic routing algorithm on this topology. When the topology changes, the action of omitting rules from tables is applied only on routes including omitted or modified links and the rules related to missing routes should be deleted. Finally, the proposed method is compared with the L2_multi method (method used in POX controller). Results show that the proposed method decreases the average delay.