DNP3
Definition
DNP3 (Distributed Network Protocol) is a SCADA protocol for reliable telemetry and control between a master (control center) and outstations (RTUs/PLCs), supporting time-stamped events, report-by-exception, and robust operations over noisy or long links.
Examples
- A utility control center polls remote substations with class scans while outstations send unsolicited events for alarms.
- An outstation executes a Select-Before-Operate sequence to open a breaker via a control relay output block (CROB).
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DNP3 is widely used in electric, water, and pipeline SCADA because it works well over unreliable or bandwidth-limited links. It separates data into time-stamped events and static snapshots, supports report-by-exception, and provides control actions designed to reduce accidental operations. Classic DNP3 was built for reliability, not security; modern profiles add authentication and, when carried over TCP, can be paired with TLS for confidentiality.
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