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

I support this response as well.

-----Original Message-----
From: owner-stds-802-3-poep@xxxxxxxx
[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Hugh Barrass
Sent: Tuesday, July 07, 2009 10:51 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


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.



David Law wrote:

>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
>draft response to the IEEE P802.3at DTE Power Enhancements Task Force 
>during the plenary week in July. The draft response will be consider
>then voted upon at the closing IEEE 802.3 Working Group plenary as part
>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 [ 
>Best regards,
>  David Law
>  IEEE 802.3 Working Group Chair