A Clustered SDN Architecture for Large Scale WSON

Software defined network (SDN) allows the rethinking of traditional approaches to network design and architecture. The distribution of the unified control-plane can be necessary in several SDN scenarios, particularly for large scale inter-domain optical networks. Distribution is necessary in inter-domain networks due to privacy issues, and can be necessary in large networks to improve scalability and management. This paper proposes a new architectural model in which network elements are grouped by proximity (in clusters) around distributed SDN controllers. The Open Flow protocol with wavelength switching extensions is used for intra-cluster control while inter-cluster coordination is performed by a new control application. The proposed model is applied to large-scale wavelength switched optical networks (WSON) and is validated by simulation. The results show that to increase the number of controllers is not justifiable if the only concern is the setup time performance. However, a multi-cluster approach is advantageous when light paths are created more frequently between nearby nodes. Also, the clustered SDN can be successfully used in a multi-administrative domain, because inter-domain light paths can be created while keeping the privacy of the network information within a cluster.