Safety-critical networks often have stringent real-time requirements; they must also be resilient to failures. In this paper, we propose the RealFlow framework that uses commodity software-defined networks (SDNs) to realize networks with end-to-end timing guarantees, while also: (a) increasing resiliency against link/switch failures and (b) increasing network utilization. The use of SDNs in this space also improves the management capabilities of the system due to the global visibility into the network. RealFlow is implemented as a northbound SDN controller application compatible with standard OpenFlow protocols with little to no runtime overheads. We demonstrate feasibility on a real hardware testbed (Pica8 SDN switches+Raspberry Pi endhosts) and a practical avionics case study. Our evaluations show that RealFlow can accommodate 63% more network flows with safety-critical guarantees when compared to current designs and up to 18% when link resiliency (via backup paths) is also considered.

Real-time systems (RTS) require end-to-end delay guarantees for the delivery of network packets. In this paper, we propose a framework to reduce the management and integration overheads for such real-time (RT) network flows by leveraging the capabilities of software-defined networking (SDN) - capabilities that include global visibility and management of the network. Given the specifications of flows that must meet hard real-time requirements, our framework synthesizes paths through the network. To guarantee that these flows meet both, their bandwidth and end-to-end timing requirements, our framework solves a multi-constraint optimization problem using a heuristic algorithm. We use exhaustive emulations and experiments on hardware switches to demonstrate our techniques and feasibility of our approach. As a result of this work, SDNs become “delay-aware” and thus can be adapted for use in safety-critical and other delay-sensitive applications.