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Steve and all, Regardless of the discussion now it is
clear from last IEEE meeting presentations the following:
Yair From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Mike, As I wrote to Yair this morning, the Task
Force already agreed (almost unanimously if I recall correctly) that the new
standard would definitely allow “medium” power (up to 30W) on
2P. A 2P PD would still need to work with either endspan or midspan,
therefore 2P=SS (and SS will never go away completely for reasons of backward
compatibility with 802.3af). However, nobody (that I’m aware of)
is still talking about using SS for high power. That debate seems to be
over, and DS won. So 4P=DS. But DS would be required only for
high-power (>30W) PDs. Let’s recap:
These bullets reflect my best
understanding of the general consensus of the group at present. (If
anyone thinks this doesn’t reflect the general consensus, please let me
know.) BTW, I use 30W for this example, but of
course that is still tentative on the decision about the max allowable current
on 2P. So this number will probably change. And “13W”
is how much an Af-PSE can supply, at the PD-end of the cable. Steve From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Steve, This seems like (yet another) another
problem with SS, not DS. The problem with identification as you diagramed
on your slide#5 is that the PD has a SS input. If the PD has separate signature control
over each pair, then it would take power from whichever PSE could supply it, as
determined in the classification stage. …/Mike
From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Yair, I think you missed the point. The solution is NOT to
“…mandate separate signatures for each 2P…” because we
also want “medium power” on 2P. The Task Force already
agreed to this. So there will be some PDs in the 15W to 30W(?)
range that have an input structure like an Af-PD (SS with diode bridges). The obvious upgrade path for a user would
be to add a medium-power At-midspan in-line with his existing Af-endspan.
These two PSEs can’t share the load since the PD is SS. So the
At-midspan has to supplant (take the place of) the Af-endspan. I showed a method to assure the midspan
will power the MP PD every time. I think this will be essential to the
802.3at standard. Steve From: Steve and all, The problem shown in this presentation can
be easily solved by mandating detection and classification signature for every
2P in the PD. Specifically separate signatures for each
2P and not a common one as measured at the RJ45. See attached presentation in page 13 for
the proposed scope of work. This is the idea of how standard can be
simplified. Doing the above is not requiring any
special specifications from the PSE. The Endspan PSE will detect and classify
pair A. The Midspan PSE will detect and classify
pair B. Both channels will turned on within the
current 802.3af timings or similar to it. Since each channel A and B are not tied
together at the diode bridge output, the PD can be operated easily by using the
PD circuitry which is TBD (implementation independent). Yair From:
owner-stds-802-3-poep@xxxxxxxx [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of Guys, I think I’ve solved another problem that’s
inherent with DS. See the attached pdf. (Only about 10 more tough
problems to go!) I’d sure appreciate some comments. Steve |