Timing Analysis of TSN-Enabled OPC UA PubSub

Industrial automation is changing towards a flat and highly interconnected architecture, with requirements for end-to-end real-time enabled machine-to-machine communications. Technologies such as time-sensitive networking (TSN) and OPC Unified Architecture (OPC UA) publish-subscribe provide the necessary features. While TSN is well explored, OPC UA's execution time behavior remains unknown. This article presents findings made while extending the open62541 OPC UA Pub Sub stack with the 802.1q VLAN tag to enable IEEE 802.1Qbv time-aware scheduling. The results include end-to-end timing measures and worst-case execution time analyses considering various payloads. Time-predictable T-CREST platforms host the publisher and subscriber, and a TSN network handles message transmission. The paper concludes by outlining further research focusing on dynamic memory access, buffer management, and the inclusion of non-priority access to the Ethernet port.