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SCADA ARCHITECTURES: MONOLITHIC SYSTEM

SCADA ARCHITECTURES: MONOLITHIC SYSTEM
What is a SCADA first generation system known as Monolithic system use for?

SCADA systems have evolved in parallel with the growth and sophistication of modern computing technology. The following sections will provide a description of the following three generations of SCADA systems:


Monolithic SCADA Systems

When SCADA systems were first developed, the concept of computing in general centered on “mainframe” systems. Networks were generally non-existent, and each centralized system stood alone. As a result, SCADA systems were standalone systems with virtually no connectivity to other systems.

The Wide Area Networks (WANs) that were implemented to communicate with remote terminal units (RTUs) were designed with a single purpose in mind–that of communicating with RTUs in the field and nothing else. In addition, WAN protocols in use today were largely unknown at the time.

The communication protocols in use on SCADA networks were developed by vendors of RTU equipment and were often proprietary. In addition, these protocols were generally very “lean”, supporting virtually no functionality beyond that required scanning and controlling points within the remote device. Also, it was generally not feasible to intermingle other types of data traffic with RTU communications on the network.

Connectivity to the SCADA master station itself was very limited by the system vendor. Connections to the master typically were done at the bus level via a proprietary adapter or controller plugged into the Central Processing Unit (CPU) backplane.

Redundancy in these first generation systems was accomplished by the use of two identically equipped mainframe systems, a primary and a backup, connected at the bus level. The standby system’s primary function was to monitor the primary and take over in the event of a detected failure. This type of standby operation meant that little or no processing was done on the standby system. Figure 3.1 shows a typical first generation SCADA architecture.

first generation scada

source: National Communication System, Technical Information Bulletin 04-1
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