DNP3 Unsolicited Responses — Push-Based Data from Outstations

Quick Answer

DNP3 unsolicited responses allow an outstation to send event data to the master immediately when changes occur, without waiting for the master to poll. This reduces alarm latency from seconds to milliseconds — critical for pipeline safety systems, leak detection, and emergency shutdown reporting.

How Unsolicited Responses Work

1. The outstation detects a change (alarm, value change beyond deadband)
2. The outstation immediately sends an unsolicited response containing the event data with timestamp
3. The master receives the response and sends a confirmation
4. If no confirmation is received, the outstation retries (configurable retry count and delay)

Configuration

Enable unsolicited responses on the outstation in the device configuration tool (Telepace Studio, PCCU32, etc.). Configure which event classes trigger unsolicited messages, the confirm timeout, and retry count.

Master Configuration

The SCADA master (Geo SCADA, Ignition) must be configured to accept unsolicited responses from the outstation. The master sends an enable-unsolicited request at startup to activate unsolicited reporting.

When to Use Unsolicited

• Critical alarms requiring immediate notification (ESD, high pressure, leak detection)
• Pipeline SCADA where polling latency is unacceptable for safety events
• Low-bandwidth links where polling creates unnecessary traffic

When to Use Polling Instead

• High-reliability applications where confirmed delivery is critical (polling provides implicit confirmation)
• Networks where unsolicited traffic from many outstations could cause congestion