Unleashing the Potential of LEO Constellations in Building Resilient and Low-Latency Control Plane for SD-WANs

Delivering seamless network services (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g.</i>, video streaming, AR/VR, and cloud gaming) in Wide Area Networks (WANs) relies on flexible traffic management, which is facilitated by Software-Defined Wide Area Networks (SD-WANs), or SDN in WANs. In SD-WANs, control and data traffic usually share the same links for cost savings, a practice known as in-band control. The SDN controller can periodically send control messages to switches via control channels for routing policy updates to maintain satisfactory network performance. However, when a link failure occurs, control channels become disconnected. Since the controller can no longer communicate with the switches, the desired flexible traffic management cannot be promised. Although backup paths can be preconfigured to reconnect some control channels, high control latency may be introduced due to the meandering routes. Fortunately, commercial Low-Earth Orbit (LEO) mega-constellations, which provide pervasive and low-latency Internet services, present a promising solution to this control resiliency issue. Inspired by the rapid deployment of these LEO constellations, we propose a novel control plane design called <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SpaceHelper</small> to leverage the LEO satellite network for improving SD-WANs’ control resiliency. <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SpaceHelper</small> smartly integrates the LEO satellite network with terrestrial SD-WAN to reconnect control channels during link failure, which is formulated as an optimization problem to minimize overall control latency. A heuristic algorithm is proposed to solve the problem efficiently and guarantee prompt control channel reconnection. Performance evaluations are conducted using the Starlink constellation and real-world WAN topologies. Compared to the state-of-the-art in-band solution, we show that <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SpaceHelper</small> can not only provide 100% resiliency, but also significantly reduce average control latency by up to 72.6% and 70.2% under GÉANT and Abilene topologies, respectively.