Developed by the OPC Foundation<\/a> and standardised as IEC 62541, OPC UA has become the de-facto communication standard for Industry 4.0, IIoT (Industrial Internet of Things), and digital transformation programmes across manufacturing, energy, oil and gas, pharmaceuticals, and critical infrastructure.<\/p>\r\n Unlike legacy industrial protocols, OPC UA is:<\/p>\r\n In plain language:<\/strong> OPC UA is the common language that allows a Siemens PLC, a Rockwell SCADA system, a cloud analytics platform, and an AI model to all understand each other – securely and without custom integrations for every pairing.<\/p>\r\n<\/blockquote>\r\n Discover our OPC UA Products<\/a><\/p>\r\n OPC Classic (1996\u20132006)<\/strong> was the original OPC standard. It solved a real problem allowing industrial devices from different manufacturers to share data – but it had a fundamental flaw: it was built on Microsoft’s COM\/DCOM technology, which meant it was Windows-only, hard to secure, and difficult to use across firewalls or wide-area networks.<\/p>\r\n As Industry 4.0 began to take shape in the mid-2000s, manufacturers needed something better. The OPC Foundation responded by designing OPC UA from scratch with a clear mandate: keep everything that worked about OPC Classic, discard the Windows dependency, and make security non-negotiable from the first line of code.<\/p>\r\n The core OPC UA specification (Part 1) was published in 2008. The protocol has been continuously updated since then, with major additions including:<\/p>\r\n Today, OPC UA is implemented by thousands of device vendors and software providers worldwide, including Siemens, Rockwell Automation, Emerson, ABB, Beckhoff, and many others.<\/p>\r\n The protocol uses a service-oriented architecture (SOA)<\/strong> built on two complementary communication models.<\/p>\r\n A client application connects to an OPC UA server, requests data, reads or writes values, subscribes to changes, and receives notifications. This is the right model for:<\/p>\r\n Introduced in OPC UA Part 14, PubSub decouples data producers from consumers. Publishers send data to a message broker (MQTT, AMQP, or UDP multicast) without knowing who is listening. Subscribers receive the data they need without connecting directly to the source. This model scales to thousands of endpoints and is ideal for:<\/p>\r\n One of OPC UA’s most powerful – and often underappreciated – features is its information model. Every piece of data exposed by an OPC UA server lives in a structured address space: a hierarchical, object-oriented model that describes not just values but their types, relationships, methods, and events.<\/p>\r\n This means that when an OPC UA client connects to a server, it can discover what data is available, what it means, and how it relates to other data – automatically and without prior configuration. This is what enables true interoperability between systems from different vendors.<\/p>\r\n Security is not an add-on in OPC UA; it was designed in from the very beginning. This is a fundamental difference from OPC Classic, where DCOM-based communication exposed serious vulnerabilities that are difficult or impossible to remediate without a full protocol migration.<\/p>\r\n Its security architecture operates at three layers:<\/p>\r\n Every connection uses TLS-equivalent encryption (128-bit or 256-bit AES) to protect data in transit. Messages are also signed, preventing tampering. Three security modes are available: None (for isolated test environments only), Sign, and Sign & Encrypt.<\/p>\r\n OPC UA supports multiple identity verification methods:<\/p>\r\n Once authenticated,th protocol enforces role-based access control (RBAC). Different users or applications can be granted different permissions – read-only access to some nodes, read\/write to others, no access to sensitive process data.<\/p>\r\n OPC Classic, introduced in the mid-1990s by OPC Foundation, was one of the first standards aimed at facilitating communications in industrial automation. The OPC specifications provided a common interface for data exchange between different systems and devices, enabling interoperability in a heterogeneous environment.<\/p>\r\n What\u2019s OPC? <\/a><\/p>\r\n Aspect<\/strong><\/p>\r\n<\/td>\r\n OPC Classic<\/strong><\/p>\r\n<\/td>\r\n OPC UA<\/strong><\/p>\r\n<\/td>\r\n<\/tr>\r\n Platform Independence<\/strong><\/p>\r\n<\/td>\r\n Tied to Windows, based on Microsoft\u2019s COM\/DCOM technology<\/p>\r\n<\/td>\r\n Platform-independent, runs on various operating systems including Windows, Linux, and embedded systems<\/p>\r\n<\/td>\r\n<\/tr>\r\n \u00a0<\/strong><\/p>\r\n Architecture<\/strong><\/p>\r\n<\/td>\r\n Uses multiple specifications for different functionalities (DA, AE, HDA)<\/p>\r\n<\/td>\r\n Service-oriented architecture (SOA), integrates all functionalities into a single, extensible framework<\/p>\r\n<\/td>\r\n<\/tr>\r\n \u00a0<\/strong><\/p>\r\n Security<\/strong><\/p>\r\n<\/td>\r\n Limited security features<\/p>\r\n DCOM presents several security vulnerabilities<\/p>\r\n<\/td>\r\n Comprehensive security features including authentication, encryption, and integrity checks<\/p>\r\n<\/td>\r\n<\/tr>\r\n Scalability<\/strong><\/p>\r\n<\/td>\r\n Not well-suited for large-scale systems<\/p>\r\n<\/td>\r\n Scalable architecture supporting a wide range of devices and applications<\/p>\r\n<\/td>\r\n<\/tr>\r\n Information Modeling<\/strong><\/p>\r\n<\/td>\r\n Basic data structures<\/p>\r\n<\/td>\r\n Advanced information modeling capabilities allowing for complex data structures and relationships<\/p>\r\n<\/td>\r\n<\/tr>\r\n \u00a0<\/strong><\/p>\r\n Interoperability <\/strong><\/p>\r\n<\/td>\r\n Compatibility issues with non-Windows platforms and modern IT infrastructures<\/p>\r\n<\/td>\r\n Enhanced interoperability with support for various communication protocols and modern IT systems<\/p>\r\n<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n <\/p>\r\n OPC Classic vs OPC UA<\/em><\/strong><\/p>\r\n\r\n
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The history of OPC UA<\/h2>\r\n
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How OPC UA works: architecture explained<\/h2>\r\n
Client-server model<\/h3>\r\n
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Publish-subscribe (PubSub) model<\/h3>\r\n
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Transport and encoding<\/h3>\r\n
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\r\n \r\nTransport<\/th>\r\n Use case<\/th>\r\n<\/tr>\r\n<\/thead>\r\n \r\n OPC UA TCP (Binary)<\/td>\r\n High-performance, low-latency connections on local networks<\/td>\r\n<\/tr>\r\n \r\n HTTPS<\/td>\r\n Internet-facing applications, firewall-friendly<\/td>\r\n<\/tr>\r\n \r\n WebSockets<\/td>\r\n Browser-based clients and web applications<\/td>\r\n<\/tr>\r\n \r\n MQTT \/ AMQP<\/td>\r\n Cloud and IIoT brokered messaging<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/div>\r\n The address space and information model<\/h3>\r\n
The security model<\/h2>\r\n
Transport security<\/h3>\r\n
Authentication<\/h3>\r\n
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Authorisation<\/h3>\r\n
OPC Classic vs. OPC UA: key differences<\/h2>\r\n
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