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Real-time capability for OPC UA

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 expansions that aim to give the OPC UA communication standard real-time capability: The first is a publisher-subscriber model; the other is utilization of the IEEE 802.1 standard for time-sensitive networking (TSN).

Publisher-subscriber model

OPC UA previously worked with a client/server mechanism. 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 publisher-subscriber 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).

With a client-server mechanism, a client requests information and receives a response from a server.
With a publisher-subscriber model, a server sends its data to the network (publish) and every client can receive this data (subscribe).

Real-time capability for standard Ethernet

The publisher-subscriber 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 expansion 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 article about OPC UA TSN.

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