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Re: [802.3af] My quest for low power PSEs continues


I believe that old hands would argue that the scope of the requirements that you uncovered was restricted to the equipment spec'd in their respective clauses.

Ergo, 7.3.2 would be limited to 10 Mb/s and might well be overridden by some more permissive text in other clauses, e.g.
14.8 MAU labeling
It is recommended that each MAU (and supporting documentation) be labeled in a manner visible to the user
with at least these parameters:
a) Data rate capability in Mb/s,
b) Power level in terms of maximum current drain (for external MAUs),
c) Any applicable safety warnings, and
d) Duplex capabilities.

It was felt by then that mandatory labeling was onerous in terms of space available on newer equipment.


At 03:28 PM 1/22/2003 -0500, Mike_S_McCormack@xxxxxxxx wrote:


One of the persistent complaints about my request to allow small single
port PSEs (see comments 169 and 170) is that the IEEE can not mandate
labeling.  Well, I was casually reading the great opus and as I was closing
in on the first 150 pages of the spellbinding text, I notice the following
little item:

  7.3.2 Signaling rate
    . . . To facilitate the configuration of operational
    systems, DTE and MAU devices shall be labeled with
    the actual signaling rate used with that device . . .

My initial reaction was that this was an obvious mistake, the 802.3 group
would never has required labeling.  While it was obviously for a good
reason, someone must have messed up.

I read on, then to my wonderment I came across: Jacket marking
    The cable jacket shall be marked in a color
    contrasting with the background color of the jacket.
    The markings shall be spaced at 2.5 m 5 cm
    regularly along the entire length of the cable. . . .

Now I was confused, our forbearers not only had committed the sin of
labeling in good faith, but apparently they had done it to the most mundane
level imaginable.  With two "shall"s in adjoining sentences no less!  (Read
after the text I quoted and you find they even request a specific color for
the cable, but that is just a request, not a requirement.)

Well, now I was curious, what else could have been so important that the
giants who walked the standard before us could have deemed it necessary.
Then I found the most interesting text: Power consumption
    . . .
    The FOMAU shall be labeled externally to identify
    the maximum value of power supply current required
    by the device when the AUI mechanical connection
    is implemented.
    . . .

So the founding fathers thought power was so important that they required a
label for it.  As a matter fact, as I slogged through the rest of the
document I discovered that when power was specified on an external
interface, there was just as likely a specification for labeling.

I therefore put forward that there is sufficient precedence within 802.3 to
allow us to require labeling of PSE output capabilities.  If you feel that
a label on the device is not sufficient to warn people about how much power
they can expect, we could also require that vendors documentation contain
the power rating, the precedent for that is:

  27.6 Repeater labeling
    It is required that each repeater (and supporting
    documentation) shall be labeled in a manner visible
    to the user with these parameters:

I think, if informing the user of the limitations of low wattage PSEs is a
barrier to legitimizing them, we can force the disclosure.  Once the user
can look on the device and see if it is suitable for their needs, what is
to keep us from filling that need?