TSN and Pub/Sub
Until now, OPC UA has had its limitations when it comes to complex processes with real-time requirements. This is why the OPC Foundation is working on two extensions that aim to give the OPC UA communication standard real-time capability: The first is a publish-subscribe model; the other is utilization of the IEEE 802.1 standard for time-sensitive networking (TSN).
Until now, OPC UA has used a client/server mechanism, where a client requests information and receives a response from a server. This system has its limitations in cases when there are many nodes on the network. The publish-subscribe model, in contrast, enables one-to-many and many-to-many communication. A server sends its data to the network (publish) and every client can receive this data (subscribe).
Real-time capability for standard Ethernet
The publish-subscribe model alone is insufficient for achieving OPC UA real-time capability. That's why the OPC Foundation is also implementing Time-Sensitive Networking (TSN). TSN is an extension of the IEEE 802 Ethernet standard to include various real-time functions. An exact timeframe in which data is transferred can also be specified.
Automotive industry is driving TSN development
With the automotive industry driving development of TSN, the required semiconductor components will be available very quickly and relatively inexpensively. The automotive industry would also like to handle all control tasks and applications that require functional safety over Ethernet. For this to be possible, they will need cycle times in the real-time range and deterministic network behavior.
Additional information concerning TSN can be found in this technical report about OPC UA TSN.