DNP3 (Distributed Network Protocol) is a set of communications protocols used between components in process automation systems. Its main use is in utilities. The data, examples and diagrams in this manual are included solely for the concept or product description and are not to be deemed as a statement of. This page provides a free overview to DNP3. It is composed of slides excerpted from our DNP3 Subcription video. DNP3 Protocol Layers Overview, 4.

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Introduction to DNP3

DNP3 Distributed Network Protocol is a set of communications protocols used between components in process automation systems. Its main use is in utilities such as electric and water tuorial. Usage in other industries is not common. It was developed for communications between various types of data acquisition and control equipment. Competing standards include the older Modbus protocol and the newer IEC protocol.

While IEC was still under development and had not been standardized, there was a need to create a standard that would allow interoperability between various vendors’ SCADA components for the electrical grid.

The protocol is designed to allow reliable communications in the adverse environments that electric utility automation systems are subjected to, being specifically designed to overcome protofol induced by EMIaging components their expected lifetimes may stretch into decadesand poor transmission media.

Although the protocol was designed to be very reliable, it was not designed tuotrial be secure from attacks by hackers and other malevolent forces that could potentially wish to disrupt control systems to disable critical infrastructure.

Because smart grid applications generally assume access by third parties to the same dnnp3 networks and underlying IP infrastructure of the grid, much work has been done to add Secure Authentication features to the DNP3 protocol. Some vendors support encryption via bump-in-the-wire for serial communications or virtual private networks for Internet Protocol-based communications. This standard was subsequently withdrawn March 27, These include not just encryption but other practices that enhance security against well known intrusion methods.


The DNP3 protocol has significant features that make it more robust, efficient, and interoperable than older protocols such as Modbusat the cost of higher complexity.

It provides multiplexing, data fragmentation, error checking, link control, prioritization, and layer 2 addressing services for user data. It also defines a Transport function protoccol similar to the function of layer 4 and an Application Layer layer 7 that defines functions and generic data types suitable for common SCADA applications.

It makes heavy use of cyclic redundancy check codes to detect errors. The improved bandwidth efficiency is accomplished through event oriented data reporting. The Remote Terminal Unit monitors data points and generates events when it determines that the data should be reported for example, when it changes value.

These events are each placed in one of three buffers, associated with “Classes” 1, 2 and 3. In addition to these, Class 0 is defined as the “static” or current status of the monitored data.

This causes the Remote Terminal Unit to send all buffered events and also all static point data to the Master station.

Following this, the Master polls for the event data by reading Class 1, Class 2 or Class 3. The reading of the classes can all be performed together or each class can be read at a different rate, providing a mechanism to create different reporting priorities for the different classes.

After an Integrity Poll, only significant data changes are sent. This can result in significantly more responsive data retrieval than polling everything, all the time, irrespective of whether it has changed significantly. The Remote Terminal Unit can also be configured to spontaneously report Class 1, 2, or 3 data, when it becomes available.

Overview of the DNP3 Protocol

The DNP Protocol has time stamped variants of all point data objects so that even with infrequent RTU polling, it is still possible to receive enough data to reconstruct a sequence of protocil of what happened in between the polls.


The DNP3 protocol has a substantial library of common point-oriented objects. The focus of this extensive library was to eliminate the need for bit-mapping data over other objects, as is often done in many Modbus installations. For example, floating point number variants are available, so there is no need to map the number on to a pair of protool bit registers. This improves compatibility and pgotocol problems such as endianness.

A Remote Terminal Unit for the DNP3 protocol can be a small, simple embedded device, or it can be a large, complex rack filled with equipment.

The protocol is robust, efficient, and compatible with a wide range of equipment, but has become more complex and subtle over time. Increasingly demanding industrial applications are part of the challenge. Also, SCADA concepts are technically simple but field applications that integrate several types of equipment can become complex to set up or troubleshoot due to variances in vendor implementations. IEEE Std has been deprecated.

The version of the standard includes features for Secure Authentication Version 5. The previous version of secure authentication in IEEE used pre-shared keys only.

The new version is capable of using Public Key Infrastructureand it facilitates remote key changes. From Wikipedia, the free encyclopedia. P P P P P Retrieved from ” https: All articles with unsourced statements Articles with unsourced statements from Portocol Views Read Edit View history.

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