PROTOCOLS FOR INDUSTRIAL NETWORKING

The protocols interfacing exchanges of data in a standard and formal way are not all linked with a specific network or technology. Some of these protocols do not have any specifications related to the hardware, or any specifications about the way to transport the data. A protocol can be implemented as a software protocol, as a hardware protocol, or both.

These protocols try answering to specific demands and to specialized needs, while benefiting of network infrastructures in place with the objective of carrying the data from a point towards another. Some of these protocols can be used as they are in well defined contexts, but they are often encapsulated in the protocols of the networks they are using, considering them like a vehicle. A significant part of these protocols can use several very different network infrastructures to dispatch the data towards destination, such as OPC or DNP3 for instance.

Thus, this classification tends to be blurred : many of the protocols used inside the Ethernet network technologies could satisfy this definition. It is the case for the Modbus protocol, which is a « generalist » protocol, and it is the case for IO-link, Drivecom, MACRO and SERCOS which are specialized protocols used in motion control networking or in sensors and actuators networking.

OPC is an open connectivity system for factory automation and for process control that support industry. Interoperability is assured through the creation and maintenance of open standards specifications.

This paper written by Thomas J. BURKE presents the specifications of OPC-UA, the main features including the UML, the XML, the S88 and the S95 standards usage, improving the robustness, the reliability and the flexibility.

iebmedia.com

The OPC foundation supplies the interoperability in factory automation by creating and by maintaining a set of open specifications. Its objectives are to standardize communication for process data, alarms, events, historic data and batch process informations between different control systems and the production devices. These devices could be sensors, actuators, instruments and interfaces, logic controllers ( PLC ), operator panels ( MMI ) or SCADA systems and more.

• What is OPC ?
• White papers.

https://opcfoundation.org

« Opcconnect.com » is a site dedicated to the needs of the software / solutions developers working with OPC where Mr Mike DILLAMORE provides a set of OPC resources.

• OPC and OPC-UA presentation and history.
• Links to others OPC related sites.
• Code samples, components, toolkits, for different languages ( C++, delphi, XML-DA … )

• Training
• DCOM security resources.

www.opcconnect.com

DNP3 is a multi-drop and master-slave distributed network protocol especially designed for SCADA communications for power systems. It was originally developed by GE-Harris in 1993, and then becomes an open standard especially designed and compliant to power industries, particularly for electric power production and distribution. This technology is now controlled by the DNP user group which gathers all the actors in the industry interested in DNP3, including vendors and services.

One particular point according to the SCADA systems in relation with the power supply industries is to need a high level of availability, a high level of measurement accuracy and high security. Another particular point is collecting small quantities of data from a large number of remote sites. To take in account these particularities and in order to obtain efficient communications, the protocol only use the layers 1 ( physical layer ), 2 ( links layer ) and 7 ( application layer ) of the OSI model.

This digital communication system is designed to work with a great interoperability between local area networks ( LAN ) and wide area networks ( WAN ), and allows to collect data towards a master server from concentrators, programmable logic controllers or some other intelligent electronic devices ( IED ).

The organization manages all which concern the protocol. It presents the last news, the evolutions of the protocol, an overview about it, its main features and the benefits we could get with, a list of resources and of documentation.

www.dnp.org

« Triangle microworks » is a commercial company supplying solutions for communication protocols development. It provides freely a list of educational papers such as white papers, overviews, slides, XML usage and more, and a list of educational videos introducing the DNP3 protocol.

www.trianglemicroworks.com

Answering questions about the protocol by the company which built the protocol. It is talked of DNP3 in comparison with other protocols, of the application layer, of interoperability, of openness, of peer-to-peer communications and many other subjects.

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This document reports on the development and the implementation of an automated electric power distribution system using the DNP3 protocol. It has been written by Mr R. P. GUPTA and Mr S. C. SRIVASTAVA.

R. P. Gupta and S. C. Srivastava.

Indian Institute of Technology in Kanpur.