DNP 3.0

Introduction

Distributed Network Protocol 3 (DNP3) is a set of communications protocols used between components in process automation systems. Its main use is in utilities such as electric and water companies. Usage in other industries is not common. It was developed for communications between various types of data acquisition and control equipment. It plays a crucial role in SCADA systems, where it is used by SCADA Master Stations (a.k.a. Control Centers), Remote Terminal Units (RTUs), and Intelligent Electronic Devices (IEDs). It is primarily used for communications between a master station and RTUs or IEDs. ICCP, the Inter-Control Center Communications Protocol (a part of IEC 60870-6), is used for inter-master station communications.

Source: https://en.wikipedia.org/wiki/DNP3

Elseta’s DNP3 stack has both Master and Slave protocols implemented. Both of them are able to serve multiple serial (over physical RS-485 line), TCP or TLS (over TCP) connections with high efficiency.

IEEE-1815 defines 4 subset levels (1-4) that consist of the objects and function codes that must be supported by the master and outstation. Levels 1-3 are supported fully and level 4 is supported partially. To get more information about how DNP3 works and what capabilities are supported one should get a copy of protocol specification and/or check Slave Interoperability List/Configuration guides for both Master and Slave protocols.

To set up TLS connection for both DNP3 Master and Slave, refer to sections Excel configuration and Certificates. All keys and certificates should be provided in the PEM format.

If no configuration is set up, DNP3 Master and Slave services are not started.

DNP 3.0 Master

Default group and variation sets are used to send commands. If slave devices support different groups and variations, they can be adjusted in Excel configuration. For more information check section Excel configuration.

Table. Default command variations:

Signal Type Command Variation

Binary Output Command 

Group12 Var1
Analog Output Command  Group41 Var1

DNP 3.0 Slave

Default group and variation sets are used to send static and event values. If master devices support different groups and variations, they can be adjusted in Excel configuration. For more information check section Excel configuration.

Table. Default signal variations:

Signal Static Variation Event Variation

Binary

Group1 Var2 Group2 Var1
Analog

Group30 Var1

Group32 Var1

Double Bit Binary

Group3 Var2

Group4 Var1

Binary Output Status

Group10 Var2

Group11 Var1

Counter

Group20 Var1

Group22 Var1

Frozen Counter

Group21 Var1

Group23 Var1

Analog Output Status

Group40 Var1

Group42 Var1

Octet String

Group110 Var0

Group111 Var0