Runtime reconfiguration of time-sensitive networking (TSN) schedules for Fog Computing

Fog Computing is about to tremendously impact the industrial automation industry. While, today's industrial automation systems use proprietary technology to provide real-time and dependability guarantees, Fog Computing enables a paradigm shift from this proprietary operations technology (OT) to the usage of standard IT equipment and infrastructure. Thus, Fog Computing is one of the key elements of the Industrial Internet of Things and Industry 4.0. In particular, future Fog Computing will be enabled by: the increased usage of IP-protocols, e.g., standardized Deterministic Ethernet solutions from IEEE Time-Sensitive Networking (TSN) Task Group, upcoming 5G wireless standards, and interoperability standards such as OPC Unified Architecture (OPC UA). In this paper, we address the runtime reconfiguration of TSN-based Fog Computing platforms. We assume that the Fog Computing platform is composed of several heterogeneous Fog Nodes interconnected using TSN. The applications consist of hard real-time control tasks, which have strict timing requirements expressed as hard deadlines. For time-critical traffic, TSN uses the scheduled traffic type, which relies on Gate-Control Lists (GCLs) at each outgoing port of a network switch to decide the transmission of scheduled frames. We propose a heuristic algorithm to determine the GCLs at runtime such that the deadlines are satisfied and the queue usage is minimized, to accommodate non-critical traffic. The scheduling algorithm is part of a configuration agent that reacts to network changes and reconfigures the GCLs using the NETCONF network configuration protocol. Our experimental evaluation shows that the scheduling heuristic is able to quickly find good-quality GCLs.