[8023-POEP] Fw: Rejected posting to STDS-802-3-POEP@xxxxxxxxxxxxxxxxx

[Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx>]

----- Message from Robert E Lounsbury <relounsbury@xxxxxxxxxxxxxxx>
on Wed, 8 Jul 2009 06:38:06 -0400 -----

To:	Hugh Barrass <hbarrass@xxxxxxxxx>
cc:	owner-stds-802-3-poep@xxxxxxxx, STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject:	Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments

Hello  Hugh, Dave, 

Please read the liaison letter.  Please disregard the damaged device.
 The damaged device only served to start the discussion in IEC.  The
letter is asking two very basic questions that might precipitate some considerations
in the specification.  First Dave mentions noise coming from the device
loads back onto the channel. This was one of the questions in the letter.
 Dave alludes to violating the specification.  Please point to
where in the specification where noise produced and coupled back to the
PoE channel is defined, limited or otherwise discussed.  Second the
letter asks if the PoE TG has considered analyzed what might happen if
there is Radiated, conducted or other environmental noise in the area where
the PoE system is installed might cause problems during the probing process.
This has nothing to do with any design flaws of a product but merely the
environment.  If you consider Industrial noise levels as defined by
IEC out of the scope for 802.3at, then please respond indicating so. Then
we might be in a position to disallow PoE in industrial.    Thanks
for your time 
  
  
  
Regards

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

Hugh Barrass <hbarrass@xxxxxxxxx>
Sent by: owner-stds-802-3-poep@xxxxxxxx

07/07/2009 01:51 PM

Please respond to
Hugh Barrass <hbarrass@xxxxxxxxx>

To	STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
cc
Subject	Re: [8023-POEP] Liaison letter from IEC TC65/SC65C/JWG10 - Power over Ethernet performance in industrial environments

David,

I can see that the liaison from IEC has caused some interesting 
discussion amongst PoE experts (and myself), however I think that we are
being asked to comment on what may well be design flaws in specific 
products and I do not think that is a healthy discussion within 802.3.

I suggest that we should send a reply along the following lines:

==========================================

The problems described in your liaison spurred some vigorous discussion
amongst our task force members regarding possible causes for the damage
that you describe. However the members are not aware of any similar 
reports that might indicate a systemic problem with 802.3 compliant 
equipment. It is the opinion of the members of IEEE P802.3at Task Force
that the standard allows product manufacturers to build reliable and 
interoperable equipment that will meet the requirements for supplying 
power over Ethernet in many environments. However, the standard does not
define how a manufacturer must build the product to ensure reliability
or how an installer should ensure that the media is suitable for correct
operation within the standard. We suggest that you should work with the
equipment manufacturers involved to determine whether the failure is the
result of a systemic problem with the standard and whether a specific 
amendment may be required.

With respect to the bit error rate performance of 802.3 links when power
is being supplied over the same link, the members of IEEE P802.3at Task
Force believe that a compliant system supplying power over an 802.3 link
will not perturb the channel sufficiently to degrade the performance of
the underlying link. However, it is the responsibility of the product 
manufacturer to ensure that noise introduced by the load does not couple
to the link and violate the power over Ethernet specifications or the 
channel specifications required for the link. Similarly it is the 
responsibility of the system installer that the channel characteristics
are met in the presence of environmental noise.


===========================================

Hugh.

David Law wrote:

>All,
>
>The IEEE 802.3 Working Group has received a liaison letter from IEC
>TC65/SC65C/JWG10, Industrial process measurement, control and 
>automation/Industrial networks with respect to Power over Ethernet
>performance in industrial environments. 
>
>I just wanted to inform you that I intend to delegate the generation
of a 
>draft response to the IEEE P802.3at DTE Power Enhancements Task Force
>during the plenary week in July. The draft response will be consider
and 
>then voted upon at the closing IEEE 802.3 Working Group plenary as
part of 
>the IEEE P802.3at closing report. You therefore may wish to review
the 
>letter prior to the meeting, the letter can be accessed at the URL
[ 
>http://www.ieee802.org/3/minutes/jul09/0709_IEC_SC65C_JWG10_to_802_3.pdf
>].
>
>Best regards,
>  David Law
>  IEEE 802.3 Working Group Chair
>
>  
>