in the provision of IoT services, Cloud Computing (CC) plays a very important role (see my figure: Cloud Computing, Fog Computing and Roof Computing in IoT). In order to enable such IoT services, in which only small latency times are possible, so-called Fog Computing (FC) is used. To realize FC, fogs, a kind of "mini cloud", are installed in a multitude on the Internet border near WSANs.
One can go one step further – namely: In order to enable "content-aware real-time IoT services", a new type of computing, the so-called Roof Computing (RC), can also be realized. The standardization committee
IEEE develops the "Standard 1931.1": Standard for an Architectural Framework for Real-time Onsite Operations Facilitation (ROOF) for the Internet of Things.
To realize Roof Computing, ROOF components, a kind of "roof mini clouds", are installed in the IoT access area in Access Gatewys or even in WSANs. The provision of "content-aware real-time IoT services" creates a hierarchical, tree-like structure of networking clouds, fogs, and ROOFs. To evaluate the availability of distributed systems based on hierarchical structures, my article "Service availability evaluation of hierarchical systems" provides the mathematical formulas. With the formulas presented there, various "Real-time IoT Services" can be evaluated based on hierarchical structures of clouds, fogs and ROOFs.
Good luck and best regards
Anatol Badach
Service availability evaluation of hierarchical systems