OPC Unified Architecture (UA) is a platform-independent, service-oriented protocol design that integrates all the functionality of the individual OPC Classic specifications into one extensible specification framework. This approach accomplishes functional equivalence to OPC Classic, with all COM OPC Classic specifications mapped to UA. It also achieves platform independence with support for ARM/x86, Windows/non-Windows, and security, including encryption, signing, and authentication. Extensibility, the ability to add new features without affecting existing applications, and information modeling, which creates standard and custom information structures from unstructured data, are also key components of OPC UA.
OPC UA provides a single, secure, and reliable cross-platform framework for accessing a variety of data. In OPC “Classic,” each protocol is its own standard with no relation to or compatibility with one another. Services (read, write, etc.) unique to each protocol are used to access unique data within each model. With OPC UA, services are abstracted from the information models they can access. Client applications programmed to be aware of the information model they want to access can use a common set of services to obtain the data.
First released in the mid-1990s, the original OPC standard abstracted PLC-specific protocols (such as Modbus, DeviceNet, etc.) into a common API allowing HMI/SCADA systems to interface with “middleware” that would convert generic OPC read/write requests into device-specific requests. The technology took hold, and an entire industry of products emerged that allowed systems to be implemented using best-of-breed products seamlessly interfacing via OPC. First iterations of the OPC standard were restricted to Windows operating systems, and thus the acronym OPC was derived from “OLE (object linking and embedding) for Process Control.” The OPC Classic specifications, as they are now known, have been widely adopted across multiple industries. As manufacturing systems and organizations evolved, industries faced new challenges, including security and data contextualization. The OPC Foundation developed OPC UA to address these needs and to provide a feature-rich, extensible platform that was scalable and future-proof.
OPC UA was designed to enhance and surpass the benefits of OPC Classic. Though functionally equivalent to OPC Classic, OPC UA is capable of far more.
Platform Independence
OPC UA supports a large range of Windows and non-Windows systems, from devices as small as embedded microcontrollers to large, cloud-based server infrastructure.
Security
OPC UA offers robust security options like user authentication and access controls, as well as the use of industry-standard Transport Layer Security (TLS) for message signing and message encryption.
Functional Equivalence
Just like OPC Classic, OPC UA offers helpful features to speed integrations like OPC server discovery, address space browsing, and data change subscriptions. OPC UA also supports on-demand, procedural commands like explicit reads and writes often critical for process control.
The OPC UA specification offers functionally equivalent features to the individual OPC Classic specifications, as well as many more. OPC UA contains several modeling and behavior specifications, including Data Access, Historical Access, Alarms and Conditions, and the pub/sub communication model, in addition to supporting specifications like Services, Mappings, Profiles, and Security. The extensibility of OPC UA allows for specifications to be added or changed while mitigating the impact on existing UA-enabled applications.
The fast and secure OPC UA Binary TCP protocol offers industrial HMI, SCADA, and other OT systems the security, flexibility, and performance required for modern process control and data acquisition.
OPC UA’s built-in authentication features allow applications to apply granular, roles-based access controls for any object present within the OPC UA server.
OPC UA is well-suited to safely move industrial data through secure network barriers like firewalls. As part of the base standard, OPC UA offers client/server protocol support with only a single, user-selected TCP port utilized to host the connection on the server side. This limits the number of inbound ports required for data access between secure layers and upper network levels, increasing security and reducing business risk.
The flexibility of OPC UA namespaces allows node IDs from external sources, including other OPC UA servers to be automatically sourced and rendered in a single, concise address space, reducing integration time and system complexity.
OPC UA offers critical features necessary for safe and secure connectivity and data acquisition for Industry 4.0 efforts, including access controls, encryption, data contextualization, and modeling.
OPC UA helps to enable good security practices for process control and data acquisition for SCADA/HMI and Industry 4.0/Digital Transformation within modern industrial systems.
The OPC UA specification facilitates the interoperability and information exchange required for successful Industry 4.0 efforts. Its ability to provide modern, secure cross-platform data exchange, coupled with support for client/server and pub/sub messaging types, creates an opportunity for diverse network topologies and application stacks. Its support for standard and custom information models allows an organization to provide structure to unstructured data as close as possible to the systems generating the data in the model and format that best fits the organization’s unique needs.
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