The edge gateway

The Edge gateway is the core of the edge device. The main responsibility of the Edge Gateway is to connect to the industrial data source to gather the data and send it to the I-IoT Hub through an internet protocol, such as MQTT, CoAP, HTTPS, or AMQP.

The most important components of the Edge Gateway are the Industrial Adapter and the IoT Adapter. The Industrial Adapter usually subscribes to the data from the industrial field and publishes it on a data bus. Typically, it implements the connector or connectors for the selected device, acting as a data source in our I-IoT data flow and making them available on the Edge data bus. The IoT Adapter, on the other hand, grabs the industrial data from the data bus and forwards it to the IoT Data Hub. An important part of the Edge gateway is the Store-and-Forward component. This is a general mechanism for storing the data in temporary local storage to make the data-transfer resilient to the instability of the network. We discussed this previously when analyzing Historians.

In the Edge gateway, the store-and-forward component is crucial since the data transfer occurs over the internet in a Wide Area Network (WAN) rather than in a Local Area Network (LAN). In a WAN, the instability and the latency of the connectivity channel is very high. The store-and-forward mechanism can either offer a limited memory buffer that covers a short period of connectivity downtime, or a large and specific storage area on a disk drive that can cover a long period of connectivity downtime or a huge flow of data. The range of the time window for which the data transfer must be ensured depends on the specific scenarios and the physical resources of the edge memory and storage.