Generations of SCADA Systems
SCADA systems have grown from simple to sophisticated with rapidly changing technology and the time line can be divided into three generations:
1. Monolithic SCADA Systems:
Owing to their origins in times when computing revolved around standalone ‘Mainframe computers’ with networks being virtually non-existent. The communication between RTU and the central computer was a dedicated line solely for that purpose. The protocols developed by vendor were to suit their own market and offered neither flexibility of functionality nor inter-market operatibility. Redundancy was provided by connecting a similar mainframe at the bus level which continuously monitored and took over the main computer in case of failure.
2. Distributed SCADA Systems:
Using the LAN networks to its advantage, the computing load was distributed across multiple systems, each system being given a specific function like communication processor, calculation processor, database server etc. and sharing information in real time. This had a limitation of geographical extent and could not be used for widely distributed systems. The parts where LAN protocols were proprietary, vendors developed their own protocols optimized for SCADA systems. The use of WAN to provide communication between the RTUs and the main distributed system remained unchanged.
3. Networked SCADA Systems:
Based on the second generation, it follows open system architecture than being vendor controlled environment. Using Open standards mitigates many limitations allowing cross vendor compatibility and the use of any off-the-shelf standard product. This made vendors move out of hardware manufacturing and put companies like HP, Compaq and Sun Microsystems in the game of hardware manufacturing. The use of WAN networks like Internet Protocol for communication has separated the Main master station from the network by the use if an intervening communications server, thus adding another layer of security to the data and improved disaster survivability.
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