Scalability of Kura-extended Gateways via MQTT-CoAP Integration and Hierarchical Optimizations

The introduction of innovative Internet of Things (IoT) gateways, powered by efficient support protocols and tools, has the potential to boost IoT development and related opportunities. Some first open-source platforms and solutions have been developed along that direction, primarily with the goals of targeting device limitations in terms of available resources and of simplifying management operations in heterogeneous environments. This paper originally proposes a multi-protocol IoT gateway solution with the specific and main goals of enabling efficiency and scalability via proper MQTT-CoAP integration. To this purpose, we have extended the Kura framework, which exploits only MQTT for machine-to-machine communication, by implementing a significant CoAP support for scalable hierarchy-based coordination, capable of externally exposing any kind of resource with REST APIs. The paper also reports an extensive set of in-the-field measurements that show the scalability of the proposed prototype that, to achieve the desired performance, also exploits some original optimizations introduced by our work on both Kura and Californium frameworks.