A Comparative Analysis on Resource Discovery Protocols for The Internet of Things

Resources discovery is a fundamental requirement to the full realization of the vision of Internet of Things. Discovery includes resource properties, capabilities, and metadata. It enables consumers to build IoT applications and services that utilize "smart things" with no prior knowledge about these things. This paper studies three of the most commonly used discovery protocols, CoAP, MQTT, and UPnP. We compare between their performance and behavior in IoT deployments. Each protocol is implemented and deployed on a mobile phone as a client and a Raspberry Pi as a broker/server. The implementation includes a WeMo switch and a TI SensorTag as resources. The paper provides insights on the different features, behavioural attributes, and a comparative analysis between these protocols. We also present performance indexes of each protocol in terms of memory and CPU usage, latency, and traffic exchange between a publisher and a subscriber. Our analysis shows that despite the three protocols are fundamentally different and each one has pros and cons, they are all highly useful in IoT environments. However, CoAP is generally more flexible and scalable, but requires a higher memory footprint.