Notes on a control network
A control network is a group of nodeseach with one or more sensors or actuators, plus localized computational capabilitythat communicates over one or more medium using a standard protocol to implement an application.
A control network may have three nodes or 300 or 30,000 or more. It may be a simple alarm controlled by a remote occupancy sensor or a city's traffic management system, monitoring and controlling signal lights, traffic flow, the actions of emergency vehicles, power distribution, or others.
Communication among the nodes may be peer to peer (distributed control) or master/slave (centralized control). Computational capability in the nodes permits the distribution of processing loads (sensors can be intelligent, for example, performing local data analysis, conversion, and normalization and reporting only significant changes in their environment).
By distributing the control functions, the system's performance and reliability are dramatically enhanced.
As to the comparison of control and data networks, although the two have much in common, they also have distinctly different design goals. A data network is concerned primarily with data throughput; a control network considers reliability, responsiveness, and predictability to be of greater concern.