Re: [802.3af] My quest for low power PSEs continues
Mike-
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.
geoff
At 03:28 PM 1/22/2003 -0500, Mike_S_McCormack@3com.com wrote:
Ladies/Gentlemen:
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:
8.4.2.2 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:
9.9.3.2 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?
Mike