Tolerating SDN application failures with LegoSDN

Despite Software Defined Network’s(SDN) provenbenefits, there remains significant reluctance in adopting it. Among the issues that hamper SDN’s adoption two stand out: reliability and fault tolerance. At the heart of these issues is a set of fate-sharing relationships: The first between the SDN-Apps and controllers, where-in the crash of the former induces a crash of the latter, and thereby affecting availability; and, the second between the SDN-App and the network, where-in a byzantine failure e.g., black-holes and networkloops, induces a failure in the network, and thereby affecting network availability. The principal position of this paper is that availability is of utmost concern – second only to security. To this end, we present a re-design of the controller architecture centering around a set of abstractions to eliminate these fate-sharing relationships, and make the controllers and network resilient to SDN-App failures. We illustrate how these abstractions can be used to improve the reliability of an SDN environment, thus eliminating one of the barriers to SDN’s adoption.