Welcome to OPC UA over TSN: A New Frontier in Ethernet Communications

When ICONICS first started developing its IoTWorX™ end-to-end software solution, the company wanted to make sure it had its bases covered in terms of integration with the most popular (and, of course, secure) communication protocols. For IoT gateways, also sometimes referred to as IoT edge devices, this meant ensuring compatibility with a wide variety of both Northbound and Southbound communications technologies.

“Northbound” data connectivity involves communication from connected equipment via the IoT edge devices to the cloud. It needs to be highly secure and utilizes a publish/subscribe (“Pub/Sub”) mechanism. Protocols such as Advanced Message Queuing Protocol (AMQP), Message Queuing Telemetry Transport (MQTT), Hyper Text Transfer Protocol Secure (HTTPS), and Representational State Transfer (REST) / JavaScript Object Notation (JSON) are most often used here.

IoT devices also communicate “Southbound” from the gateway itself to on-premises industrial equipment, sensors, and machines. For process, factory, and building automation applications, the communication protocols involved typically include industry standards such as Modbus, BACnet, SNMP, web services, or other proprietary communications technologies. When development began on ICONICS IoTWorX, the company made certain to include the OPC Unified Architecture (OPC UA) at the core of its architecture.

The combination of IoTWorX with OPC UA allows for continuation of the standard Pub/Sub mechanism and ensures integration of the plant floor with the enterprise. In addition, IoTWorX uses two IIoT messaging protocols recommended by the OPC Foundation itself in AMQP and MQTT.

The OPC UA protocol standard was initially developed to expand and evolve. Recently, the concept of Time-Sensitive Networking (TSN) in conjunction with OPC UA is being discussed more and more in the automation industry. For those not yet familiar with the technology, TSN is an extension of the Ethernet standard involving the recognition of, and appropriate handling between, time-sensitive data and general data being transferred over a shared network. The desired end result is the creation of a deterministic network, where:

  • All clocks on all nodes are synchronized to a uniform network time.
  • Time-critical data can be assured to be transmitted within a guaranteed amount of time, while other non-time-restricted data can be sent as normal.

UA Pub/Sub requires a broker that can distribute messages from publisher to subscriber. The load of the publisher does not depend on the number of subscribers. The broker is responsible for handling that load and is required to scale when the number of subscribers increases. UA Pub/Sub may use a broker such as an IoT Hub or MQTT broker, etc., to send data across the Internet. When using UA Pub/Sub in a LAN (where TSN would typically be integrated), broadcast messages are used and, in that case, the network hardware itself acts as a broker.