A Software-Defined Networking (SDN) Assisted Middleware Interconnecting Supervisory Control and Data Acquisition (SCADA) Systems

The reliable operation of critical infrastructure systems is of significant importance to society. The power grid and the water distribution system are two critical infrastructure systems, each of which is facilitated by a cyber-based supervisory control and data acquisition (SCADA) system. Although critical infrastructure systems are interdependent with each other due to coupling (a power grid may be the electrical supply for a water distribution system), the corresponding SCADA systems operated independently and did not share information with each other. Modern critical infrastructure systems tend to cover a larger geographic area, indicating that a SCADA control station supervising a small area is far from meeting the demands.

In this thesis, the above-mentioned problem is addressed by building a middleware to facilitate reliable and flexible communications between two or more SCADA systems. Software Defined Networking (SDN), an emerging technology providing programmable networking, is introduced to assist the middleware. In traditional networks, network configurations required highly skilled personnel for configuring many network elements. However, SDN separates the control plane from the data plane, making network intelligence logically centralized, and leaving the forwarding switches with easy commands to follow. In this way, the underlying network infrastructures can be easily manipulated by programming, supporting the future dynamic network functions.

In this work, an SDN-assisted middleware is designed and implemented with open source platforms Open Network Operating System (ONOS) and Mininet, connecting the power grids emulator and water delivery and treatment system (WDTS) emulator EPANet. Since the focus of this work is on facilitating communications between dedicated networks, data transmissions in backbone networks are emulated. For the interfaces, a multithreaded communication module is developed. It not only enables real-time information exchange between two SCADA control centers but also supports multiple-to-multiple communications simultaneously. Human intervention is allowed in case of emergency.

SDN has many attractive benefits, however, there are still obstacles like high upgrade costs when implementing this technique. Therefore, rather than replace all the routers at once, incremental deployment of hybrid SDN networks consisting of both legacy routers and programmable SDN switches is adopted in this work. We emulate on the ratio of SDN deployment against the performance of the middleware and the results on the real dataset show that a higher fraction of SDN results in a higher reliability and flexibility of data transmissions. The middleware developed may contribute to the development of the next-generation SCADA systems.