MQTT at the Transport Level

[piperoc]

File: /en/202305/a-comparison-of-iiot-protocols-mqtt-sparkplug-vs-opc-ua.md

The MQTT is shows at the Transport Layer of the OSI model. I am not sure this is accurate as it makes it look like an alternative to TCP/IP. I believe MQTT to be at the Application Layer, and requires TCP/IP as transport.

[joey8869]

Agreed, MQTT is indeed an application layer of the OSI. However, MQTT is always used as a transport layer for other protocols like OPC UA and Sparkplug to ensure end-to-end message delivery. To me, it is doubtful that MQTT is an application layer of the OSI.