Advancing user-space networking for DDS message-oriented middleware: Further extensions

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 user-space DDS networking transport extensions, allowing us to fast-track 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). Building on this, we additionally offer two more extensions to the second most performant implementation FastDDS, also based on DPDK and XDP, and realize novel optimizations not present in the original extension implementations. We evaluate each extension’s performance benefits against four existing DDS implementations (OpenDDS, RTI Connext, FastDDS and CycloneDDS). The DPDK-based and XDP-based extensions offer a performance benefit of 31%–38% and 18%–22% reduced mean latency, respectively, as well as an increase in bandwidth and sample rate throughput of at least 160%, while reducing the latency bound by at least 93%, demonstrating the performance and dependability advantages of circumventing the kernel for real-time communications.