On the performance of OPC UA and MQTT for data exchange between industrial plants and cloud servers

Abstract

The Internet of Things (IoT) is a key technology in the development of Industry 4.0. An increasing number of new industrial devices are expected to communicate with each other by means of local (edge) and cloud computing servers. In this article, two well-known protocols used for IoT and Industrial IoT (IIoT) are compared in terms of their performance when they are used to send/receive data to/from cloud servers. Due to their wide diffusion and suitability, the considered protocols are open platform communication-unified architecture publisher-subscriber (OPC UA PubSub) (purposely developed and maintained by industrial consortia) and message queuing telemetry transport (MQTT), the most well-known message protocol originally developed by IBM. The performance comparison is carried out considering the overall quantity of the data transferred (user payload plus overhead) and the roundtrip time required to send in data and receive a feedback message in return. The experimental results include the evaluation of several cloud computing server and application scenarios, highlighting how each protocol is particularly suitable for certain situations. Finally, conclusions about the best choice for data exchange between devices are given.