Häufig gestellte Fragen
What does OPC UA mean and what is the standard used for?
OPC UA stands for Open Platform Communications Unified Architecture and is an open, vendor-independent communication standard defined in the IEC 62541 series of standards and maintained by the OPC Foundation. It governs the exchange of data between machines, controllers and higher-level software, describing not only how data is transferred but also — via an object-oriented information model — what it means. This allows production data to be transported with unambiguous semantics all the way into business systems, which is why OPC UA is regarded as a foundational technology for Industry 4.0. In the ERP environment, the standard typically serves as the interface between manufacturing and order, warehouse and costing data.
Does OPC UA replace older OPC variants?
Yes, OPC UA is increasingly replacing classic OPC (with the DA, A&E and HDA profiles). The main reason is that the old Classic technology was built on Microsoft's COM/DCOM under Windows, whereas OPC UA runs platform-independently on embedded controllers, servers, and in Linux, Windows and cloud environments. Added to this are an integrated security concept and the semantic information model, which Classic OPC does not offer. In practice, some classic OPC installations in existing plants remain in operation, but new projects are as a rule designed for OPC UA.
How much effort does integrating OPC UA into an ERP system involve?
The effort depends above all on whether the machines already provide an OPC UA server and which data is actually needed in the ERP. With modern controllers featuring a native OPC UA server, connecting one machine type is usually manageable; with older machines, a gateway or an OPC UA wrapper often has to be placed in front. In many architectures, OPC UA is not connected directly to the ERP but via a middleware or integration platform that consolidates the data and passes it on, for example via a REST API. Decisive for data quality and maintainability is clean modelling, i.e. defining which OPC UA nodes are mapped to which ERP fields.
How secure is OPC UA and how is the communication encrypted?
OPC UA has security firmly anchored in its specification and provides mechanisms for authentication, encryption and signing via X.509 certificates. The standard defines three security modes: None with no protection at all, Sign with signature only for integrity assurance, and SignAndEncrypt with additional encryption of the payload. Good practice is to use at least SignAndEncrypt with a policy such as Basic256Sha256 in production environments and to disable the insecure None mode. Since many servers offer the native opc.tcp service on TCP port 4840 by default, this should also be restricted to a dedicated production network via firewall rules and not exposed to the internet unprotected.
What is the difference between OPC UA and MQTT?
OPC UA and MQTT pursue different approaches and in practice are often combined rather than played off against each other. MQTT is a lightweight publish-subscribe protocol that distributes messages efficiently via a broker but does not itself define what the transferred data means. OPC UA, by contrast, comes with an extensive semantic information model and describes machines, devices and values in a standardised way, which is why its specification runs to well over a thousand pages across all its parts. In typical Industry 4.0 architectures, OPC UA is frequently used for standardised machine communication while MQTT is used for efficient connection to cloud platforms; with PubSub, OPC UA also supports its own event-driven pattern, which can use MQTT as a transport, among others.
What are OPC UA Companion Specifications?
Companion Specifications are supplementary information models developed by industry and association bodies that define uniform data structures on top of the OPC UA core for specific device or machine types. They ensure that, for example, machine tools, robots or injection moulding machines from different manufacturers use the same terms and structures and can thus be connected in a more interchangeable way. Well-known examples are the umati initiative for machine tools driven by the VDW, and the EUROMAP specifications for plastics processing, which are published under the umbrella of the OPC Foundation. With several dozen Companion Specifications now published and numerous others in development, OPC UA enables broad, cross-industry interoperability beyond pure data transfer.