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
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.
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
c) Any applicable safety warnings, and
d) Duplex capabilities.
- 14.8 MAU labeling
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
port PSEs (see comments 169 and 170) is that the IEEE can not
labeling. Well, I was casually reading the great opus and as I was
in on the first 150 pages of the spellbinding text, I notice the
7.3.2 Signaling rate
. . . To facilitate the configuration of
systems, DTE and MAU devices shall be labeled
the actual signaling rate used with that device . .
My initial reaction was that this was an obvious mistake, the 802.3
would never has required labeling. While it was obviously for a
reason, someone must have messed up.
I read on, then to my wonderment I came across:
188.8.131.52 Jacket marking
The cable jacket shall be marked in a color
contrasting with the background color of the
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
labeling in good faith, but apparently they had done it to the most
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
the cable, but that is just a request, not a requirement.)
Well, now I was curious, what else could have been so important that
giants who walked the standard before us could have deemed it
Then I found the most interesting text:
184.108.40.206 Power consumption
. . .
The FOMAU shall be labeled externally to
the maximum value of power supply current
by the device when the AUI mechanical connection
. . .
So the founding fathers thought power was so important that they required
label for it. As a matter fact, as I slogged through the rest of
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
allow us to require labeling of PSE output capabilities. If you
a label on the device is not sufficient to warn people about how much
they can expect, we could also require that vendors documentation
the power rating, the precedent for that is:
27.6 Repeater labeling
It is required that each repeater (and
documentation) shall be labeled in a manner
to the user with these parameters:
I think, if informing the user of the limitations of low wattage PSEs is
barrier to legitimizing them, we can force the disclosure. Once the
can look on the device and see if it is suitable for their needs, what
to keep us from filling that need?