A Highly Available Software Defined Fabric

Existing SDNs rely on a collection of intricate, mutually-dependent mechanisms to implement a logically centralized control plane. These cyclical dependencies and lack of clean separation of concerns can impact the availability of SDNs, such that a handful of link failures could render entire portions of an SDN non-functional. This paper shows why and when this could happen, and makes the case for taking a fresh look at architecting SDNs for robustness to faults from the ground up. Our approach carefully synthesizes various key distributed systems ideas -- in particular, reliable flooding, global snapshots, and replicated controllers. We argue informally that it can offer high availability in the face of a variety of network failures, but much work needs to be done to make our approach scalable and general. Thus, our paper represents a starting point for a broader discussion on approaches for building highly available SDNs.