Increasing Resilience of SD-WAN by Distributing the Control Plane Extended Version

Modern WAN interconnects utilize SD-WAN to automatically respond to network changes and improve link utilization, latency, and availability. Therefore, they incorporate controllers with a centralized view, which collect network state from managed gateways, calculate suitable forwarding actions, and distribute them accordingly. However, this limits the robustness and availability of the network control plane, especially in the event of node or partial network outages. In this paper, we propose a distributed and highly robust SD-WAN control plane without any central or regional controller. Our solution can handle arbitrary device failures as well as network partitioning. The distributed forwarding decisions are based on user-defined, dynamically evaluated path cost functions, and consider not only path quality but also quality fluctuations. The evaluation shows that our approach can handle several thousand SD-WAN gateways and hundreds of network policies in terms of computation. Further, the communication overhead introduced due to its distributed architecture is discussed and shown to be negligible compared to a central approach. This paper is an extended version of our work published in altheide2023. It describes the information transmitted between sites as well as a strategy for deploying policies, discusses approaches reducing communication bandwidth, introduces grouping of multiple flows without requiring explicit coordination, and provides a detailed analysis of the bandwidth required.