OsmoTECH XT Single-Sample Micro-Osmometer Service Guide
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Appendix C:
OPC-UA Features and
Configuration
C.1 OPC-UA overview
1
The Open Platform Communications Unified Architecture
(OPC-UA) is a platform-independent, service-oriented
architecture that integrates all of the functionality of
each OPC Classic
2
specification into one extensible
framework.
This multi-layered approach achieves these original and
enhanced OPC design goals.
Refer to
Functional equivalence
OPC-UA adds these enhancements to the OPC Classic:
•
Support for discovery of available OPC servers on
local PCs and networks.
•
A hierarchical representation of data in the address
space—for example, files and folders—allowing for
discovery of simple and complex structures for use by
OPC clients.
•
Reading and writing of data/information on demand
based on access permissions.
•
Monitoring of data, information, and events, and
report-by-exception when values change based on a
client’s criteria (known as
subscriptions).
•
Clients can execute programs, etc., based on methods
defined on the server.
Cross-platform support
Platform independence is an essential OPC-UA
component. This protocol provides the necessary
infrastructure for interoperability, supporting commonly-
used hardware platforms across the enterprise, from
machine-to-machine, machine-to-enterprise and
everything in-between.
OPC-UA is also cross-platform in terms of software, and
is not tied to any one operating system or programming
language.
1 Source:
https://opcfoundation.org/about/opc-technologies/opc-ua/
2 See
https://opcfoundation.org/about/opc-technologies/opc-classic/
Security
The OPC-UA security implementation is firewall-friendly
while addressing security concerns by providing a suite
of controls, such as:
•
Transport
options,
such as the ultra-fast OPC-binary
transport or the more universally compatible SOAP-
HTTPS.
•
Session encryption
, with messages transmitted
securely using 128-bit or 256-bit encryption levels.
•
Message signing
, which ensures that messages are
received exactly as they were sent.
•
Sequenced packets
, which eliminates the exposure to
message replay attacks.
•
Authentication
using OpenSSL certificates, which
identifies each UA client and server and provides
control over which applications and systems are
permitted to connect with each other.
•
User control
that can require users to authenticate—
through login credentials, certificate, etc.—for use of
applications and data.
•
Auditing
that logs activities by user and/or system and
provides an audit trail.
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. The existing OPC
Classic specifications were modeled into UA profiles
which can also be extended by other organizations.
