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Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments



Hi Chad,
 
I agree with Geoff on the question of compliance.
 
My suggestion regarding non-PD impedance statements in the PHY clauses was not intended as a comment against 802.3at, but rather it should be considered as a maintenance item.
 
The question with regard to noise tolerance of the PSE detection criteria still stands. I was there, but not directly involved in the criteria determination. Somebody else have a comment on this?

Dan Dove
----
Principal Engineer, LAN PHY Technology
ProCurve Networking by HP
 


From: owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Geoff Thompson
Sent: Wednesday, July 01, 2009 2:25 PM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments

Chad-

I would assert that your statement is not correct.

While it is true that
"Clause 33 has long been a standard part of 802.3 and compliance to 802.3
means compliance to Clause 33 even if you aren't doing PoE."
Clause 33 has not been part of 802.3 for nearly as long as clause 25 has.
The criteria for what constituted a
"standard compliant 802.3 100BASE-TX device"
was set in stone well before the start of the 802.3af project.
It was the job of the 802.3af project to work with compliant legacy equipment.
100BASE-Tx would fall into that category.

I would be very surprised there is a statement anywhere in the standard that says that all RJ45 twisted pair PHYs that do not implement clause 33 have to comply with the requirements of clause 33.

There certainly is no global statement in the standard that says you have to comply to the portions of the standard that you are not implementing.

Geoff

On 6/30/09 12:52 PM, Chad Jones (cmjones) wrote:
If this is true: 

"If this is a "standard compliant 802.3 100BASE-TX device", it
apparently has a termination network that will lead a PSE to believe
it's a PD." 

doesn't that make it non-compliant? 

Clause 33 has long been a standard part of 802.3 and compliance to 802.3
means compliance to Clause 33 even if you aren't doing PoE.


-Chad

-----Original Message-----
From: owner-stds-802-3-poep@xxxxxxxx
[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Dove, Daniel
Sent: Tuesday, June 30, 2009 11:54 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 -
Power over Ethernet performance in industrial environments

David,

If this is a "standard compliant 802.3 100BASE-TX device", it apparently
has a termination network that will lead a PSE to believe it's a PD.

When 802.3af originally chose the PD detection criteria, it was based
upon broad industry experience and evaluation of many devices, but its
possible that somebody "less experienced in Ethernet design" might
incorporate termination networks that could falsely indicate a PD
signature. 

Perhaps we need to include language in the copper PHY MDI specs that
indicates the impedance between the pairs of a non-PD shall not fall
within a valid PD range of impedances?

Dan Dove
----
Principal Engineer, LAN PHY Technology
HP ProCurve Networking

-----Original Message-----
From: owner-stds-802-3-poep@xxxxxxxx
[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of David Law
Sent: Thursday, June 18, 2009 3:46 AM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 -
Power over Ethernet performance in industrial environments

All,

I have been asked to forward this information by Bob Lounsbury. It
addresses a number of the questions and comments that there have been on
the reflector in respect to this liaison letter.

Best regards,
  David


----- Forwarded by David Law/GB/3Com on 18/06/2009 11:43 -----


Hello David,

I am sending this email to you as I am currently not part of the IEEE
reflector site. Please distribute this email to your committee and any
other IEEE 802.3 sub committee you feel is necessary.

I have gone through the IEEE thread in attempts to extract out the
questions and then attempted to answer them.  First attached is a
picture of the PCB that is mentioned in the letter.
The damage was due to a misapplied POE power.  Reasons unknown, but as
you can see when this happens the result is very destructive (see
Enet_PHY.jpg). If this would have been a POE device it would have been a
PD, however this device is a standard implementation of 802.3 100BaseTx
device.


Answers to comments and questions;

1) The Liaison letter is not asking for application support, the words
"application support" does not exist in the letter.  There is a question
regarding noise isolation back on the cabling caused by POE devices and
how this may have an effect on BER of the channel. The paragraph is
trying to determine if in the development of POE(+), transient noise
caused by the PD's changing load has been considered and if attempts
have been made to limit the noise.  We want to know if there is high
dv/dt noise on the power in a POE channel if this will impact the BER
performance of that specific channel.

I am sorry if we assumed that IEEE members had knowledge of the MICE
environmental concept. This concept has been and become part of the
following standards.  TIA 568C.0, TIA 1005, ISO/IEC 24702, ISO/IEC TR
29106, IEC61918 and some of the IEC fiber specifications.  The "E" of
the MICE details possible noise types and levels in environments ranging
from commercial (office) to harsh industrial environments.

I do not know what standard contains 33.4.1 (I assume IEEE 802.3), the
device pictured below that was mentioned in the liaison letter is a
compliant, standard 802.3 100BaseTX device that does not make use of
POE(+) portion of the standard. There for it is not a PSE or PD device
and never should have received power from the PSE. Why it may have has
had power applied prompted the concerns in IEC SC65C/JWG10.

Regarding the Ideas for response;

I have gone through the email chains and extracted out the questions and
comments.  I have attempted to address each one below.  Also I have
included a picture of at least one device that was damaged by
miss-application of POE power so you can see the results when a PSE
applies power when it should not.

1) It is understood that the primary concern of IEEE 802.3 standard
committees (aside of the protocol) is the technical aspects of the
network performance as a whole. However in the development of the
physical layer
(PMD) portion of the standard, grounding is discussed, shield RJ45
connectors are required and most of all 1500 volt isolation transformers
are specified. In addition there is a mention of BER performance in 1V
pk to pk noise.  Intrinsic to the component specifications defined by
the IEEE
802.3 standard and the standards referenced by IEEE 802.3 are safety
requirements/noise performance requirements.  All of this is irrelevant
to the liaison letter as it does not discuss any safety aspects. The
primary question is "if electrical noise was considered during the
development of the POE(+) standard" specifically during the power
probing process.

2) Not sure what this statement means with regards to the questions in
the letter, however, if environments E2 and E3 cannot be supported by
the IEEE
802.3 standard please let us know ASAP as Ethernet is moving into the
industrial areas where E2 and E3 environments are more common at an
extremely fast pace. The industrial community needs to know if we are at
risk with any part of the network including POE(+). We have asked and
received higher balanced cabling specifications and higher common mode
attenuation specifications to help mitigate some of the noise issues.

3) Yes standards such as IEC 61000 require a certain level of
performance be met in the presence of noise defined in these standards
and test fixturing.  We are asking if IEEE 802.3 has considered these
requirements (or any other) in the design, specification from everything
beginning at the protocol to signaling, adaptive filters and component
definitions.

With regards to "hardening against these kinds of environments being
outside the project scope"  again the as I read the letter, it is not
asking for any change to the specification or requirements, it is asking
if noise was considered, and if it was and POE(+) is not compatible with
these noise types and levels, please indicate that, so we can take the
appropriate action in our standard. If it was not, someone needs to
determine the suitability of POE(+) in high noise environments.

Thanks for your time and I look forward to any additional questions or
comments.


Regards
(Embedded image moved to file: pic27067.gif) Rockwell Automation Bob
Lounsbury - Principal Engineer
   Control and Visualization Business
   1 Allen-Bradley Drive, Mayfield Heights, OH. 44124
   Tel:    +1.440.646.4297
   Fax:   +1.440.646.3076
   Cell:   +1.440.610.4485
   email: relounsbury@xxxxxxxxxxxxxxx



 

 David_Law@

 3com.com

 

 
To 
 06/04/2009          Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx>

 08:34 AM
cc 
                     gwood@xxxxxxx, russof76@xxxxxxxxx,

                     shariff07724@xxxxxxxxx, Terry Cobb

                     <trcobb@xxxxxxxxxxxx>, "McCormack, Michael"

                     <mike_mccormack@xxxxxx>, "Alan Flatman"

                     <a_flatman@xxxxxxxxxxxxx>

 
Subject 
                     Re: Fw: [8023-POEP] Liaison letter from IEC

                     TC65/SC65C/JWG10 - Power over Ethernet performance
in 
                     industrial environments

 

 

 

 

 

 

 






Hi Bob,

Thank you very much for this information.

While the formal consideration of the letter will occur during the IEEE
802.3 plenary in July, to allow maximum time for understanding and
consideration of its contents, I have provided the IEEE P802.3at DTE
Power via MDI Enhancements Task Force email reflector a preview as I
intend to delegate drafting a response to that Task Force. I have also
decided to provide a preview to the IEEE P802.3az Energy-efficient
Ethernet email reflector. While it doesn't directly relate to that
project I know that a number of PHY experts participating in that
project so may be individually interested in the letter.

Based on the above I wonder if you could have a look at the email
archive for the IEEE P802.3at Task Force - it is a public web site. The
thread in response to the preview can be found at the URL [
http://www.ieee802.org/3/poep_study/email/thrd1.html ] and I note there
were a few of questions of clarification from some of the participants.
I therefore wondered if you would like to either add to information
below I supply it to the reflector - or respond to them directly
yourself on the reflector - if you wish to join the reflector please see
the URL [ http://www.ieee802.org/3/at/reflector.html ].

While I understand that IEC TC65/SC65C/JWG10 can't provide anything
formal until they next meet - assistance that you - or anybody else -
can provide as an individual is appreciated.

Thanks and best regards,
 David



Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx> wrote on 04/06/2009
12:28:48:

  
Hello David,

As a member of SC65C/JWG10 and co-author of the letter, I wish to 
clarify the intent and concerns that precipitated the letter. This 
concern has been validated by at least one event where a PSE 
incorrectly applied power to a non-powered device.  The result was a 
burned up board and melted plastics.  The PSE in this system was 
manufactured by a large switch vendor who is active on the IEEE 802.
3 standards.  The intent of the letter is to solicit a response from 
IEEE 802.3at committee whether or not during the development of the
POE(+) standard, if noise was considered specifically during the Power
    

  
Discovery process. Additionally has anybody analyzed and tested the 
power discovery process and algorithms in the presence of noise?

In our industrial environments our expected noise levels are generally
    

  
a magnitude greater than that of the commercial environment.  Below I 
have provided an extracted partial table from the MICE table printed 
in the ISO/IEC24702 standard.  E1 is a typical description of the 
noise levels in a commercial building environment, additionally E3 is 
a typical description of the noise levels in a harsh industrial 
environment. Since the release of this standard the MICE table and 
concept has been adopted by many other standards in IEC and TIA as a 
description of environments ranging from commercial office to harsh 
industrial environments.  Many of the test procedures and requirements
    

  
for the electrical noise
(immunity) tests can be found in a series of IEC 61000 standards.

My personal feeling is that this needs to be addressed before the 
standard is released this year. This is not a cabling issue and cannot
    

  
be solved by the selection of specific types of cabling such as UTP or
    

  
STP/FTP cabling.  Each cable type has it's own noise ingress 
mechanisms that are dependant on cable balance, coupling attenuation 
performance and grounding conditions.  I hope you consider the request
    

  
from SC65C/JWG10 seriously and respond in a appropriate time so we can
    

  
continue to expand the coverage of POE(+) systems in to industrial 
applications with minimal risk to the end users.

Feel free to distribute this email to your committee  We anxiously 
await your response.


[image removed]




Regards
___________________________________________________
Rockwell Automation
Bob Lounsbury - Principal Engineer, Logix/NetLinx
   Automation Control & Information Group (ACIG)
   1 Allen-Bradley Drive, Mayfield Heights, OH. 44124
   Tel:    +1.440.646.4297
   Fax:   +1.440.646.3076
   Cel:   +1.440.610.4485
   email: relounsbury@xxxxxxxxxxxxxxx


    

(See attached file: Enet_PHY.jpg)