Performability Evaluation of Software Defined Networking Infrastructures

Software Defined Networking (SDN) has been introduced as a novel paradigm in traffic engineering, aiming to simplify network management and control through programmability concepts. This emerging strategy addresses the recent network challenges by decoupling the packet forwarding features, namely, the data plane, from the decision system, namely, the control plane, through a dedicated protocol named OpenFlow. The controller element of an SDN infrastructure represents the core entity in charge of managing the whole service logic and, being this module failure-prone, its performance and its availability are crucial issues for an accurate plan of an SDN-based network. The approaches considering both performance and availability assessment in data and telecommunication networks are frequently referred to as the performability evaluations. A performability evaluation is presented in this work to the aim of selecting the most convenient redundancy scheme of the SDN controller, where the controller has been modeled by a finite number of virtual operator instances serving different network zones. By assuming that the SDN controlling unit is described by a Continuous-Time Markov Chain with a vector state, the steady-state availability of the SDN controller in parallel redundancy configuration is computed by an approach based on the Universal Generating Function tailored for the vector case, and a redundancy optimization problem for the architecture of the SDN controller is solved.