Reliability side-effects in Internet of Things application layer protocols

With the widespread use of IoT devices in safety-critical applications, new constraints should be addressed in designing IoT infrastructures. Reliability is one of the most important characteristics of an IoT system which should be satisfied with high consideration. The way how IoT devices communicate with each other in different layers of architecture, plays an important role in building a reliable IoT infrastructure. Maintaining the desired level of reliability in IoT applications through application layer protocols, imposes a noticeable amount of overhead to different characteristics of IoT systems. In this paper, we are going to investigate these overheads through practical evaluations on a conventional IoT infrastructure. To this end, we will compare two well-known application layer protocols, i.e., MQTT with many reliable features and CoAP with fewer reliability mechanisms, from different aspects. Conducted experiments in Arduino test-beds illustrate while MQTT provides more reliable and predictable infrastructure for IoT devices, on average, it imposes 364uW of more power consumption than CoAP for delivering the same amount of data. Furthermore, utilizing MQTT as a reliable application layer protocol, imposes 4.99x of more latency in comparison with CoAP.