DNP3 is a version of the Distributed Network Protocol. DNP3 is a set of layered communication protocols used between devices and components in control and automation systems. It is primarily used for SCADA and communications between a master station and RTUs or IEDs. DNP3 is more robust, efficient, and interoperable than Modbus and other protocols. Data is defined in Classes 0, 1, 2 or 3.