By introducing programmability, automated verification, and innovative debugging tools, SoftwareDefined Networks (SDNs) are poised to meet the increasingly stringent dependability requirements of today’s communication networks. However, the design of faulttolerant SDNs remains an open challenge. This paper considers the design of dependable SDNs through the lenses of self-stabilization—a very strong notion of faulttolerance. In particular, we develop algorithms for an in-band and distributed control plane for SDNs, called Renaissance, which tolerate a wide range of (concurrent) controller, link, and communication failures. Our selfstabilizing algorithms ensure that after the occurrence of an arbitrary combination of failures, (i) every non-faulty SDN controller can eventually reach any switch in the network within a bounded communication delay (in the presence of a bounded number of concurrent failures) and (ii) every switch is managed by at least one non-faulty controller. We evaluate Renaissance through a rigorous worst-case analysis as well as a prototype implementation (based on OVS and Floodlight), and we report on our experiments using Mininet.

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