An ICS master station repeatedly communicates with field controllers through a process called “polling.” The master station will send a request for updates whereby a field controller, such as an RTU or PLC, responds by sending back the requested information. assets are polled to verify they are still functioning as expected. When the asset is polled, it sends data about it’s state back to the SCADA, and if everything is OK, it will be polled on a regular schedule. If it’s not OK, it will be polled again to determine whether a technician needs to get to the asset to perform maintenance on it.
The poll can contain a general request such as a pressure reading or it can be related to specific metrics. An example could be that the pressure has exceeded required parameters. Has it overheated? Has it seen events that would cause you to believe the life cycle is being degraded? This polling process can happen every couple of seconds, every couple of minutes, every couple of hours, days, months or years. It is dependent on the asset, the role the asset plays in a system, and the risk that asset presents.