Automated Bootstrapping of A Fault-Resilient In-Band Control Plane

Adoption of Software-defined Networking (SDN) in critical environments, such as factory automation, avionics and smart-grid networks, will require in-band control. In such networks, the out-of-band control model, prevalent in data center deployments, is inapplicable due to high wiring costs and installation efforts. Existing designs for seamlessly enabling in-band control plane cater only for single-controller operation, assume proprietary switch modifications, and/or require a high number of manual configuration steps, making them non-resilient to failures and hard to deploy. To address these concerns, we design two nearly completely automated bootstrapping schemes for a multi-controller in-band network control plane resilient to link, switch, and controller failures. One assumes hybrid OpenFlow/legacy switches with (R)STP and the second uses an incremental approach that circumvents (R)STP. We implement both schemes as OpenDaylight extensions, and qualitatively evaluate their performance with respect to: the time required to converge the bootstrapping procedure; the time required to dynamically extend the network; and the resulting flow table occupancy. The proposed schemes enable fast bootstrapping of a robust, in-band managed network with support for seamless redundancy of control flows and network extensions, while ensuring interoperability with off-the-shelf switches. The presented schemes were demonstrated successfully in an operational industrial network with critical fail-safe requirements.