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A Comprehensible Guide to Industrial Ethernet

A Comprehensible Guide to Industrial Ethernet by Wilfried VossA Comprehensible Guide to Industrial Ethernet

The topic of Industrial Ethernet is confusing for the outsider, and even technology experts are similarly puzzled by the wide-ranging and obscure collection of competing systems.

This comprehensible guide explains the basics of various Industrial Ethernet protocols, in this case, Ethernet/IP, Modbus/TCP, EtherCAT®, Ethernet Powerlink, ProfiNet, and Sercos III. The intention is to provide a significant level of educational value through comprehensive, easy-to-read, and easy-to-digest information for the newcomer to Industrial Ethernet, the engineer facing the challenge of picking the technology best suited for his application or to satisfy the curiosity of the technology-savvy person.

The book addresses the fundamentals shared by the various Industrial Ethernet protocols by explaining topics such as challenges and motivation for Industrial Ethernet, the basics and advantages of Fieldbus systems, the OSI Reference Model, the basics of Ethernet TCP/IP, and real-time control considerations.

All these topics are mandatory for understanding the differences between the various choices in the market, and thus, they are presented with a particular focus on Industrial Ethernet technologies by adding specific references.

The core of the book is, nevertheless, the chapters on Ethernet/IP, Modbus/TCP, EtherCAT®, Ethernet Powerlink, ProfiNet, and Sercos III plus a comparison of their characteristics.

Other technologies may be mentioned in passing, but the intention is to concentrate on those most significant to the North American market.

It must be emphasized that a sufficiently detailed description of each protocol involved is clearly outside the scope of this book. Complete documents are provided by the respective manufacturers or standardization/user organizations, but they usually provide little educational value, and some of these standards are only available to the organizations’ members. The intended purpose of this book is to deliver a convenient entry to understanding the topic. Also, in contrast to official documentation, the author takes the liberty of adding honest, sometimes even critical but always fair insights.

This is a work in progress. Please check frequently for updates.

Table of Contents

Chapter 1: Introduction

Chapter 2: Introduction to Fieldbus Systems

Chapter 3: Ethernet And TCP/IP Basics

Chapter 4: Industrial Ethernet Protocols


More to follow...;-)

About the Author

Wilfried Voss is the author of the “Comprehensible Guide” series of technical literature covering topics like Controller Area Network (CAN), SAE J1939, Industrial Ethernet, and Servo Motor Sizing. Mr. Voss has worked in the CAN industry since 1997 and before that was a motion control engineer in the paper manufacturing industry.  He has a master’s degree in electrical engineering from the University of Wuppertal in Germany.

Mr. Voss has conducted numerous seminars on industrial Fieldbus systems such as CAN, CANopen, SAE J1939, Industrial Ethernet, and more during various Real-Time Embedded And Computing Conferences (RTECC), ISA (Instrumentation, Systems, and Automation Society) conferences and various other events all over the United States and Canada.

Mr. Voss has traveled the world extensively, settling in New England in 1989.  He presently lives in an old farmhouse in Greenfield, Massachusetts with his Irish-American wife and their son Patrick.

For more information see his website at


This book is dedicated to my good friend, mentor, and colleague
Dr. Werner Schulze (9.24.1948 – 9.23.2010)

Throughout his professional career, he was a vivid supporter of the CAN Bus technology, and in reference to Industrial Ethernet he coined the saying: “You don’t need a Ferrari to go grocery shopping.”

His statement was not targeted against the use of Industrial Ethernet, but it continues to serve as a reminder to soberly investigate the requirements of an application without giving in to a hype.

As always, I have listened to his advice, and it does reflect in this book.

Contact the Author

Despite all efforts in preparing this book, there is always the possibility that some aspects or facts will not find everybody’s approval, which prompts us, author and publisher, to ask for your feedback. If you would like to propose any amendments or corrections, please send us your comment. We look forward to any support in supplementing this book, and we welcome all discussions that contribute to making the assessments of the various Industrial Ethernet standards as thorough and objective as possible.

To submit amendments and corrections please log on to the author’s website at and leave a note.

From the Author

The best way to become acquainted with a subject is to write a book about it.
Benjamin Disraeli

I vividly remember the first time I was confronted with the (at the time) new Industrial Ethernet protocols, in this specific case EtherCAT® and Ethernet Powerlink. I was at a trade show in Chicago and was about to hold a presentation on CANopen and its ingenious Device Profiles. However, there were two other presentations before mine, and they were about (you may have guessed it) EtherCAT® and Ethernet Powerlink.

Both presentations were held very professionally, provided convincing facts and more than just impressive technical details, and both presenters vividly and convincingly trashed the other’s technology… Oh, and each one of them claimed that their respective technology was at least one thousand times faster than CANopen, which was, of course, challenged by the opponent.

Nobody shed a tear for the real victim of their battle, namely the next presenter who, all of a sudden, was forced to justify a technology that was at least one thousand times slower than EtherCAT® or Ethernet Powerlink (I am trying to stay neutral here). These two presenters were polite enough to join the small crowd and listen to my introduction of the CANopen technology (I believe, the doors were locked).

I must admit, this was by far my worst presentation ever because my brain rotated around the devastating facts I had learned earlier. In my heart, I knew that these guys had put up a great show, however, without revealing potential shortcomings that their technologies might have in common. These guys had just been a bit too slick for my taste, and I am a stickler for honesty when it comes to presenting technical facts.

Right in time with the conclusion of my speech, I realized what they both had omitted. I ended my presentation with the statement that CANopen, despite its “shortcomings,” was still more than sufficient for more than 90% of all motion control applications in the North American market, and all that came with a significantly lower price tag than EtherCAT® or Ethernet Powerlink (Claiming a factor of one thousand was tempting, but I didn’t). The painful expression on both faces, without so much as voicing a protest, was precious.

Nevertheless, times have changed, and I will continue repeating myself by stating that I am far from making a case against Industrial Ethernet technologies, because their advantages over other established networking technologies are too convincing to dismiss them as mere hype. Industrial Ethernet technologies serve a significant number of applications that were not possible with other networking protocols (as this book will explain).

Without a doubt, Ethernet for industrial control and automation tasks is a fascinating technology.

However, and I will continue repeating that view as well, it is advisable to investigate all aspects, specifically when it comes to the determination of the application performance requirements and justification of the attached costs.

Any argument that increased costs should be seen in reference to the benefit of increased performance must pale when the level of performance is in conflicting proportion to what the application requires. To stress the point, you don’t need a Ferrari to go grocery shopping.

In the same sense, the costs of Industrial Ethernet are, without a doubt, justified when it comes to demanding automation tasks that require vast speed and real-time control, the transportation of vast amounts of data in a timely fashion, and the processing of a massive number of I/O signals. This is where Industrial Ethernet reveals its full strength.

In hindsight, I would like to thank the two presenters (who shall remain unnamed) of the EtherCAT® and Ethernet Powerlink technologies. Their introduction to Industrial Ethernet was a wake-up call for me. It reminded me that, as an engineer, you need to work hard to stay on top of new developments, and since the day of their presentations, I have worked hard to write this book.

Among many other insights I gained, my research on the topic of Real-Time Industrial Ethernet also revealed how utterly useless their verbal battle was for the attendees.

First, as this book will explain, a fair comparison of the various Industrial Ethernet protocols based on mere technical data must fail because any test results are overwhelmingly application-specific.

Secondly, while EtherCAT® and Ethernet Powerlink appear to maintain a technological edge over other, TCP/IP-based protocols, namely Ethernet/IP and Modbus/TCP, their global market share is currently at sixteen percent with no tendency to a dramatic change in the near future. “Inferior” protocols such as Ethernet/IP and Modbus/TCP (now integrated into Ethernet/IP) continue to dominate the market with a 47 percent share.

Be that as it may, the topic of Industrial Ethernet remains confusing for the outsider, and even technology experts are puzzled by the wide-ranging and obscure collection of competing systems.

I wrote this comprehensible guide to Industrial Ethernet with the intention of providing comprehensive, easy-to-read, and easy-to-digest information with a definitive emphasis on educational value.


CIP, Common Industrial Protocol, CIP Motion, CIP Safety, CIP Sync, CompoNet, CompoNet CONFORMANCE TESTED, ControlNet, ControlNet CONFORMANCE TESTED, DeviceNet, EtherNet/IP, EtherNet/IP CONFORMANCE TESTED are trademarks of ODVA, Inc. DeviceNet CONFORMANCE TESTED is a registered trademark of ODVA, Inc.

EtherCAT® is registered trademark and patented technology, licensed by Beckhoff Automation GmbH, Germany.

All other trademarks are property of their respective owners.

Limit of Liability / Disclaimer of Warranty

While the publisher and author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties or merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor author shall be liable for any loss or profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

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