There are some types of communication media are supported from PLC/RTU to central distributed SCADA systems via local and wide area networks as in any data communication network. A local area network is consisted with in a local geographical area such as a building or a campus and consists of few buildings with in closed proximity. It means a wide area network is a network that connects many local area networks spread across different cities at least 100 kilometers apart.
There are some types of wide area networks include:
• Analog multi point and point to point modem networks.
• Multi point and frame relay/cell relay type point networks.
• Satellite networks and wireless radio.
• Fiber optic based on networks.
Recently, the SCADA network may be built around many of the above possible combinations of transmission protocols and networks. It will be more computer power is to be provided from the SCADA hosts since more data is required to meet the information demands of the current day corporate networks. The network and communication environment they operate are to be continuously evaluated for improvements and upgraded as time goes by.
To meet the higher demand for the data, users, system designers and SCADA manufacturers started looking for higher speed devices. A very large existing infrastructure of microwave, phone lines, and private wire that operate at voice grade frequencies.