Adopting User-Space Networking for DDS Message-Oriented Middleware

Due to the flexibility it offers, publish-subscribe messaging middleware is a popular choice in Industrial IoT (IIoT) applications. The Data Distribution Service (DDS) is a widely used industry standard for these systems with a focus on versatility and extensibility, implemented by multiple vendors and present in myriad deployments across industries like aerospace, healthcare and industrial automation. However, many IoT scenarios require real-time capabilities for deployments with rigid timing, reliability and resource constraints, while publish-subscribe mechanisms currently rely on components that are not strictly real-time capable, such as the Linux networking stack, making it hard to provide robust performance guarantees without large safety margins. In order to make publish-subscribe approaches viable and efficient also in such real-time scenarios, we introduce userspace DDS networking transport extensions, allowing us to fasttrack the communication hot path by bypassing the Linux kernel. For this purpose, we extend the best-performing vendor implementation from a previous study, CycloneDDS, to include modules for two widespread user-space networking technologies, the Data Plane Development Kit (DPDK) and the eXpress Data Path (XDP), and we evaluate their performance benefits against four existing DDS implementations (OpenDDS, RTI Connext, FastDDS and CycloneDDS). The CycloneDDS-DPDK and CycloneDDS-XDP extensions offer a performance benefit of 31% and 18% reduced mean latency, respectively, as well as an increase in bandwidth and sample rate throughput of up to 59%, while reducing the latency bound by at least 94%, demonstrating the performance and dependability advantages of circumventing the kernel for real-time communications.