Modbus/TCP submitted to IETF

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Thread Starter

Marc Leconte

A couple of days ago Modbus/TCP was submitted to IETF as an Internet Draft.

You can find the RFC on the IETF web site at "http://www.ietf.org/internet-drafts/draft-dube-modbus-applproto-00.txt":http://www.ietf.org/internet-drafts/draft-dube-modbus-applproto-00.txt

I believe this is great. Modbus over Ethernet TCP/IP is already widely used in the industry: most of the industrial devices embedding Ethernet TCP/IP support Modbus among their application protocols.

Modbus/TCP covers the communication needs of a wide range of equipment.
Modbus/TCP is a very cost-effective solution in terms of memory/CPU requirement.
Modbus/TCP is also very easy to implement thus reducing development cost.
Establishing Modbus/TCP as an IETF RFC demonstrates that Modbus is now in the public domain.
I think this is great for scalability of Industrial Ethernet protocol stacks.
This could mean that Modbus/TCP will become the first universal application protocol running on every device with embedded Ethernet port?

Any comment on this?
Thanks,

Marc
 
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Yes, it is an "interesting step toward maturity" in the Automation use of TCP/IP.

The "www.modbus.org":http://www.modbus.org site has also been much improved.

We'll have to see how to create enough interest (discussion) at IETF to move it from Draft to formal draft RFC with a number before it expires
in Nov 2002.

Quiet drafts just die & never "earn their RFC numbers". Anyone at Modbus.Org have suggestions?

Best Regards::

Lynn August Linse, Senior IA Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected] www.lantronix.com
Tel: (949)279-3969 Fax: (949)453-7152
 
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Curt Wuollet

I just hope someone looks for patents, otherwise, good luck and Godspeed. I would be much more comfortable with a real standard, published and well.....Standardized.

Regards

cww
--
Free Tools!
Machine Automation Tools (LinuxPLC) Free, Truly Open & Publicly Owned Industrial Automation Software For Linux. mat.sourceforge.net. Day Job: Heartland Engineering, Automation & ATE for Automotive Rebuilders.
Consultancy: Wide Open Technologies: Moving Business & Automation to Linux.
 
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Peter Whalley

Hi all,

One of the ways our community can contribute to the development of an IETF is by cnsidering the issue of patents and other intellectual property that might restrict the use of the proposed Modbus/TCP standard.

Details of the IETF policy on incorporation of intellectual property in standards is documented in Section 10 of RFC 2026 (see
"http://www.ietf.org/rfc/rfc2026.txt":http://www.ietf.org/rfc/rfc2026.txt ). In essence:

1. they invite "... any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights
which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director...". Clause 10.4 B.

2. "...the IETF Executive Director shall attempt to obtain from the claimant of such rights, a written assurance that upon approval by the IESG
of the relevant Internet standards track specification(s), any party will be able to obtain the right to implement, use and distribute the technology or works when implementing, using or distributing technology based upon the
specific specification(s) under openly specified, reasonable, non-discriminatory terms..." Clause 10.3.2 C.

3. the IETF requires that: "..The contributor represents that he has disclosed the existence of any proprietary or intellectual property rights
in the contribution that are reasonably and personally known to the contributor..."

Note that the draft for Modbus/TCP was submitted by an employee of Schneider Automation Inc and an employee of Schneider Automation S.A. and that the document contains the statement "...This document is an Internet-Draft and is in full conformance with all provisions of Section 10
of RFC2026. "

We have the opportunity to:

a) advise the IETF if we think there is undisclosed intellectual property which may inhibit use of the proposed standard

b) comment on the acceptability of any terms and conditions which intellectual property owners might like to impose. The normal standards
advancement process is used to determine if terms are resonable.

In anyone thinks there are applicable undisclosed patents then please make them known to the IETF.

Regards::

Peter Whalley
Magenta Communications Pty Ltd
Melbourne, VIC, Australia
e-mail: peter*no-spam*@magentacomm.com.au
delete *no-spam* before sending
 
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Ralph Mackiewicz

IETF standards aren't real, published or standardized???

I'm curious: how would you do it?

Regards,

Ralph Mackiewicz
SISCO, Inc.
 
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Curt Wuollet

Hi Ralph

IETF standards _are_ about as real and standardized as they can get on paper. What really makes a standard is when the IETF RFC's are widely deployed and implemented in enough ways that backsliding becomes nearly impossible. Then you have an immutable, dependable, standard. This is what keeps the Internet interoperable despite repeated attempts at ownership and foils embrace, extend, and destroy tactics.

Regards

cww
---
Free Tools!
Machine Automation Tools (LinuxPLC) Free, Truly Open & Publicly Owned Industrial Automation Software For Linux. mat.sourceforge.net.
Day Job: Heartland Engineering, Automation & ATE for Automotive Rebuilders.
Consultancy: Wide Open Technologies: Moving Business & Automation to Linux.
 
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Curt Wuollet

Hi Peter.

Sage advice, and much cheaper to find out about now rather than later. How much do you want to bet that XML and SOAP are compromised in some way? .NET?

Regards

cww
---
Free Tools!
Machine Automation Tools (LinuxPLC) Free, Truly Open & Publicly Owned
Industrial Automation Software For Linux. mat.sourceforge.net.
Day Job: Heartland Engineering, Automation & ATE for Automotive
Rebuilders.
Consultancy: Wide Open Technologies: Moving Business & Automation to
Linux.
 
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Marc Leconte

Curt wrote
> IETF standards _are_ about as real and standardized as they can get on paper. What really makes a standard is when the IETF RFC's are widely deployed and implemented in enough ways that backsliding becomes nearly impossible.
--------------
I think I agree with this point.
Don't you all think that Modbus/TCP is already widely deployed and implemented in the industrial control world? Isn't is already a de-facto application protocol in the industrial world?

Modbus protocol was created by Modicon in 1979 (serial line) and ported on TCP around 1996. Since then, everyone can implement Modbus on TCP...
So what are the issues with patents or IP?
Has anyone been blocked for implementing Modbus?
Pushing Modbus as an Internet standard will
- "officialize" the de-facto standard
- formally cut the link between Modbus and Schneider/Modicon.
The benefits of Modbus/TCP becoming a standard RFC are:
- there is a single reference document for Modbus/TCP
- Modicon/Schneider do not own Modbus/TCP: future of Modbus/TCP, protocol change, etc.

Best regards,
Marc Leconte
 
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Curt Wuollet

Hi Marc
To that I say, yea, verily. Unfortunately there are several variations around. Let's hope the standard, if it comes to pass, really does
standardize. The automation world needs to move in that direction.

The patent issues I see are similar to the OPC and Samba treachery where people who adopt "standards" can later be shaken down for
licensing of patents that weren't mentioned up front. None of these Trojan Horses can ever be properly called open and exposures to risks like this will soon destroy any momentum to standardize.

Regards
cww
 
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> Curt wrote
> > IETF standards _are_ about as real and standardized as they can get on
> > paper. What really makes a standard is when the IETF RFC's are widely
> > deployed and implemented in enough ways that backsliding becomes nearly
> > impossible.

Marc Leconte wrote:
> --------------
> I think I agree with this point.
> Don't you all think that Modbus/TCP is already widely deployed and
> implemented in the industrial control world?
Isn't is already a de-facto
> application protocol in the industrial world?

Well, I agree with the statement that Modbus is widely deployed, but I don't agree that it is a 'standard'. There are many variations in the various Modbus implementations, i.e. in which functioncodes are supported, whether broadcast is supported, MSB/LSB sequence, etc.

Although I haven't used it myself, it wouldn't surprise me if similar variations for Modbus/TCP.

> Modbus protocol was created by Modicon in 1979 (serial line) and ported
> on TCP around 1996. Since then, everyone can implement Modbus on TCP...
> So what are the issues with patents or IP?
> Has anyone been blocked for implementing Modbus?
> Pushing Modbus as an Internet standard will
> - "officialize" the de-facto standard
> - formally cut the link between Modbus and Schneider/Modicon.

It depends - are you and me allowed to modify the RFC ? Or, to take the RFC, modify it, and propose it for a new RFC ?

> The benefits of Modbus/TCP becoming a standard RFC are:
> - there is a single reference document for Modbus/TCP

There is already such a document (on the Schneider website)

> - Modicon/Schneider do not own Modbus/TCP: future of Modbus/TCP, protocol
> change, etc.

This is not true. Look at all the other 'standards' that exist, either in the EN or ISO range - many a fieldbus user group has 'standardised' its system, but in the mean time has continued to extend its system. Take AS-i
for example; in the EN 50325 you'll find ASi version 1, but since the last two years we have AS-i 2.11.

Rob Hulsebos
 
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> Well, I agree with the statement that Modbus is widely deployed, but I don't agree that it is a 'standard'. There are many variations in the various Modbus implementations, i.e. in which functioncodes are supported, whether broadcast is supported, MSB/LSB sequence, etc.

I think you are failing to distinguish between the standard (over which the definers can exercise control) and the many implementations (over which the designers have absolutely no control). There *is* undeniably a Modbus standard. Equally undeniably, there are implementations that do not adhere to the standard, often because the standard does not address specific needs of specific users.

You can say much the same thing about many standards; HTML and the 'C' programming language both leap to mind. The published standard from W3C attempts to define quite specifically what is and is not legitimate HTML. Where the standard is ambiguous, or where specific server/browser developers felt they needed more than the standard was offering, the developers defined their own extensions, variations, etc. Similarly, there are several standards for 'C', each one more authoritative than the last. However, every implementer of the language is free to make it as
different as he likes; some make it different enough that they decide to call it something else.

(One benefit of an open standard is that everybody is free to use it. Another attribute - whether it's a benefit or a drawback is a matter of opinion - is that everybody is free to adhere to it as closely or as loosely as he likes.)

Back to Modbus ... I think it's less fruitful to complain that Modbus isn't a standard than it is to promote the formation of a non-partisan committee to manage the standard, consider proposals for change, release subsequent versions of the standard, possibly even certify compliance...

Regards,

Greg Goodman
Chiron Consulting
 
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