The IoT Hub: a Fog Node for Seamless Management of Heterogeneous Connected Smart Objects

The Internet of Things (IoT) will interconnect billions of devices, denoted as "smart objects," deployed pervasively, which will be extremely heterogeneous, in terms of hardware (i.e., computational power and available memory), software (i.e., operating systems, applications), and communication interfaces. Traditional Internet actors, such as personal computers, mobile devices, and cloud servers, will also communicate with smart objects, thus creating even more complexity. The IoT has so far grown as several vertical silos, with the purpose of demonstrating the concept of the IoT, rather than focusing on the actual construction of a highly interoperable infrastructure for the development of applications. The Internet Protocol (IP) stack (in particular, HTTP and CoAP) has been foreseen as the driver for integration and interoperability among devices and basis for the evolution of the Web of Things. However, in order to manage the physical diversity of devices and to create an IP-based infrastructure, the presence of network elements able to bridge different networks to enable direct end-to-end communication is required. Moreover, effective interaction with applications might require the presence of intermediaries, such as proxies, which may optionally implement protocol and data format translation functionalities. Given the above considerations, we propose a Fog node, denoted as " IoT Hub," placed at the edge of multiple networks, which enhances the networks capabilities by implementing the following functions: border router; cross-proxy; cache; and resource directory. An implementation of the IoT Hub is presented together with a performance evaluation in a real-world IoT testbed.