Academic Awards 2025 booklet

51 Improving TSN Traffic Shaping with Constant Bandwidth Server Scheduling Ethernet has long since been the prevailing standard in Local Area Networks, and more recently its use has spread to Wide Area Networks and industrial automation. However, Ethernet does not provide timing guarantees, which renders it unsuitable for timing-critical applications. Time-Sensitive Networking (TSN) is a suite of standards designed to address this limitation by defining mechanisms that provide latency guarantees for real-time communication. One such mechanism is Credit- Based Shaper (CBS), which allocates a configurable amount of bandwidth to different types of traffic by using credit. However, CBS does not always fully utilize all available bandwidth, resulting in potential inefficiencies and wasted network capacity. Our research proposes an alternative based on the Constant Bandwidth Server Scheduling (CBSS) algorithm, which is traditionally employed for task scheduling in real-time operating environments. To demonstrate the performance of CBSS, we implemented it in the P4 programming language for an Intel Tofino switch, while also comparing it to CBS on a theoretical level. We found that CBSS achieves higher bandwidth utilization and reduces worst-case and average forwarding delays for network traffic. We also laid the groundwork for an analytical model of CBSS in TSN, which, when expanded upon, can be used to exactly predict its behavior. Figure 1: Network packet transmission of CBSS with two traffic classes, where the priority is dynamically changed by manipulating the deadlines of the classes. Figure 2: Architecture of CBSS implementation in P4, showing the packet forwarding process. Shaper deadline Packet transmission Network switch Data plane Packet sent T raiffc M anager Update credit Update deadline Control Plane Get all deadlines Change class priorities Sort classes by deadline Packet arrives Packet leaves