The main purpose of a SCADA system is provide industrial control and monitoring of processes that are tangible and therefore existent in the real world. This processes monitoring and controlling is capable of being performed remotely, over long distances and in multiple ways of accessibility of the SCADA system itself.
Scada architectures are time based meaning they have changed over the years as a result of development of new technology and the adoption of new technological practices. SCADA architectures are divided into three generational parts: the first generation of SCADA systems with monolithic architecture, the second generation, whose systems architecture was distributed and the third and most recent architecture where the architecture is described as networked.
In the Monolithic architecture consisted of independent systems run on mainframe computers. There was no communication between systems because networks were non existent.
In the distributed architectures, processing was specified to and done by smaller stations communication with each other through local area networks with proprietary protocols.
Adoption of standard protocols for communication gave birth to networked architecture. Systems with this architecture have relatively secure connections and are usually very numerous in a set up.