An Analysis of Hierarchical Software-Defined Network Control Plane: A Reliability Approach

Present-day computer systems have drastically transformed from the ones in days of basic file sharing, peripheral sharing or the hosting of companywide applications on a server to much more sophisticated, small and faster systems. These systems have further expanded to include cloud-based networks, virtualized desktops, servers, etc. The capabilities of evolving heterogeneous computer systems require advanced control plane. Software-defined networking (SDN) proposes to control the network from a centralized controller instead of a distributed configuration. SDN makes it easier for network operators to evolve network capabilities. Even though SDN proposes a logically centralized system, the controllers may not represent a single, centralized device, instead the control plane may consist of logically centralized but physically distributed controllers wherein each controller manages different administrative domains of the network or different parts of the flow space. There are mainly two types of control plane architecture: flat control plane and hierarchical control plane. In this paper, we have analyzed the reliability and availability of the hierarchical SDN control plane. We take into consideration workload capacities of the controllers, link failures, node failures and controller-end failures to determine the reliability of the system.