The Gateway Network can be utilized to collect Tags at remote sites and share them with a central Ignition Gateway. However, in some cases it is preferable to use the IIoT Architecture instead. Below are a couple reasons why.
IIoT uses the MQTT protocol, which is incredibly lightweight and efficient, making it ideal in scenarios when connections to a remote PLC are achieved via Satellite or Cellular communication. Additionally, it can safely support a large number of devices without placing a large strain on the network.
Adding new nodes to IIoT Architecture is simple and cost efficient. New Edge Gateways or MQTT-Enabled Devices can be deployed with minimal effort, while keeping costs low.
Is MQTT replacing OPC-UA?
Absolutely not! The two protocols will continue to coexist, as they currently do. MQTT is a great light-weight protocol that is ideal for communicating with devices when available bandwidth is limited. If your Gateway is attempting to communicate with a PLC over a cellular or satellite connection, then an MQTT solution may be a better fit than OPC-UA.
The following are key pieces in the IIoT Architecture.
A Field Device of some sort can be used to connect to a PLC. This device also needs to be able to publish Tag values to an MQTT server. Any of the following hardware can act as a Field Device:
An MQTT Broker is a server that can communicate with your Field Devices via MQTT. This can be an Ignition Gateway with the MQTT Distributor Module installed, or a third-party server, such as a Chariot MQTT Server.
A subscriber is some application that subscribes to topics in the Broker. In regards to Ignition, this is the Gateway with the the MQTT Engine Module installed.
More details on the MQTT modules can be found in the Cirrus LInk documentation.