What is OPC UA?
The OPC Unified Architecture (UA), released in 2008, is a platform independent service-oriented architecture that integrates all the functionality of the individual OPC Classic specifications into one extensible framework.
This multi-layered approach accomplishes the original design specification goals of:
- Functional equivalence: all COM OPC Classic specifications are mapped to UA
- Platform independence: from an embedded micro-controller to cloud-based infrastructure
- Secure: encryption, authentication, and auditing
- Extensible: ability to add new features without affecting existing applications
- Comprehensive information modeling: for defining complex information
Functional Equivalence
Building on the success of OPC Classic, OPC UA was designed to enhance and surpass the capabilities of the OPC Classic specifications. OPC UA is functionally equivalent to OPC Classic, yet capable of much more:
- Discovery: find the availability of OPC Servers on local PCs and/or networks
- Address space: all data is represented hierarchically (e.g. files and folders) allowing for simple and complex structures to be discovered and utilized by OPC Clients
- On-demand: read and write data/information based on access-permissions
- Subscriptions: monitor data/information and report-by-exception when values change based on a client’s criteria
- Events: notify important information based on client’s criteria
- Methods: clients can execute programs, etc. based on methods defined on the server
Integration between OPC UA products and OPC Classic products is easily accomplished with COM/Proxy wrappers that are available in the download section.
Platform Independence
Given the wide array of available hardware platforms and operating systems, platform independence is essential. OPC UA functions on any of the following and more:
- Hardware platforms: traditional PC hardware, cloud-based servers, PLCs, micro-controllers (ARM etc.)
- Operating Systems: Microsoft Windows, Apple OSX, Android, or any distribution of Linux, etc.
OPC UA provides the necessary infrastructure for interoperability across the enterprise, from machine-to-machine, machine-to-enterprise and everything in-between.
Security
One of the most important considerations in choosing a technology is security. OPC UA is firewall-friendly while addressing security concerns by providing a suite of controls:
- Transport: numerous protocols are defined providing options such as the ultra-fast OPC-binary transport or the more universally compatible SOAP-HTTPS, for example
- Session Encryption: messages are transmitted securely at 128 or 256 bit encryption levels
- Message Signing: messages are received exactly as they were sent
- Sequenced Packets: exposure to message replay attacks is eliminated with sequencing
- Authentication: each UA client and server is identified through OpenSSL certificates providing control over which applications and systems are permitted to connect with each other
- User Control: applications can require users to authenticate (login credentials, certificate, etc.) and can further restrict and enhance their capabilities with access rights and address-space “views”
- Auditing: activities by user and/or system are logged providing an access audit trail
Extensible
The multi-layered architecture of OPC UA provides a “future proof” framework. Innovative technologies and methodologies such as new transport protocols, security algorithms, encoding standards, or application-services can be incorporated into OPC UA while maintaining backwards compatibility for existing products. UA products built today will work with the products of tomorrow.
Information Modeling
The OPC UA information modeling framework turns data into information. With complete object-oriented capabilities, even the most complex multi-level structures can be modeled and extended. Data-types and structures are defined in profiles. For example, the existing OPC Classic specifications were modeled into UA profiles which can also be extended by other organizations:
