STN: A Robust and Distributed SDN Control Plane

Abstract

This paper presents the STN, a distributed SDN control plane based on Software Transactional Memory principles that supports concurrent policy updates while ensuring consistent policy composition and high availability. In particular, STN gives network programmers an abstraction that guarantees (1) linearizability: any execution can be transformed into an equivalent sequential history and (2) wait-freeness: the control plane tolerates up to f node failures, for some parameter f. We describe an STN design using a number of tags which is asymptotically minimal to ensure the above properties. Also, we report our progresses in building an STN prototype based on the Pyretic modular programming language.