Improving the fault-tolerance of software-defined networks with dynamic overlay agreement

Software-Defined Networking (SDN) emerges as one of the leading technologies to address the pressing networking problems such as network virtualization and data center complexity issues using programmable switches and controllers. To well exchange information and have coordinated control for the SDN environment, the multi-controller SDN network has been proposed. Unfortunately, this network architecture still faces the problem of faulty controllers that may forge the command arbitrarily, and then the whole network will be broken down easily. Thus, it is important to propose the fault-tolerance scheme under the SDN network system. In this paper, a new SDN environment called the Multi-Controller Overlay Groups (MCOG) where each device is managed by the controllers is proposed. Besides, the degree of the faulty influence will be revised to define the different bounds of fault tolerance in the MCOG environment. Furthermore, the new protocol named General Dynamic Multi-Controller Agreement (GDMCA) protocol is proposed to solve the Byzantine Agreement (BA) problem in the MCOG environment. Based on the proof of complexity, it can show that the proposed GDMCA protocol is optimal under the MCOG environment.