Helix: Traffic Engineering for Multi-Controller SDN

ABSTRACTDeploying traffic engineering (TE) in the context of multi-controller SDN (MCSDN) or on WANs is challenging due to state and consistency requirements. For example, using strong consistency to ensure that information is always up-to-date introduces significant performance overheads. However, using eventual consistency to reduce synchronisation time comes at the expense of using outdated information to make decisions. We design and implement Helix, an MCSDN system that supports deployment on WANs. Helix offloads operations closer to the data plane and minimises shared state between devices, allowing it to tolerate high latency and mitigate state consistency concerns. We develop a lightweight TE algorithm that requires minimal state, making it suitable for use with Helix. Our simulation results show that Helix reduces congestion loss by up to 1.6x and performs 12x fewer path changes compared to CSPF.