Re: [8023-POEP] System Architecture
Hi David,
It looks fine however there is something here that worries me.
To say that a 4P PD is constructed from two separate PD means that if a
PD is a Powered DTE, a DTE is Data Terminal Equipment it means that we
have in the same box TWO data terminal equipment which is not true and
was not the intent.
The intent, at least my intent was that a DTE can get power from all 4P
while the DTE power supply make the necessary steps to make sure that
power is getting to it from a) Pair AB or Pair CD b) Pair AB and Pair CD
while each load reflected to pairs AB and Pairs CD is determined by its
class.
The PD power supply and 802.3AF/AT interface make sure that current and
voltage are kept within the PI specification.
I worry about the fact that if we define a 4P PD as totally independent
2 x 2P PDs it will be interpreted ad e.g. two IP phones enclosed in the
same box which is not the case.
One of the cases is single IP phone that its load is distributed between
single or double power source which looks as two loads to be driven by
two 2P PSEs.
I belive that we can not a void the use of a 4P PD term.
We just say that a 4P PD is a device that includes a DTE that is
connected to a 4P interface while 4P interface is actually built by 2x2P
interface.
A 2P interface is the basic building block.
The above allow using two DTEs, each of them connected to 2P interface
however this is not the typical application for a 4P PD.
I guess we just need to word it right to reflect the technical intent.
Yair
-----Original Message-----
From: owner-stds-802-3-poep@xxxxxxxx
[mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of David Law
Sent: Wednesday, June 14, 2006 4:10 PM
To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
Subject: Re: [8023-POEP] System Architecture
Hi Yair,
Here are some thoughts on what you have suggested.
Regards,
David
1. A single PD in a PoE system can get power from each 2P
simultaneously.
I'm not sure I would look at things from the point of view of the PD as
I
thought we were going to treat the 2 PDs that can be behind a single
RJ45
as two separate PDs. I would therefore suggest we look at things from
the
point of the RJ45, or using the correct Clause 33 terminology, the PI.
Based on this, and including support for legacy Clause 33 as well, I
would
suggest:
[1] A single PI can support either [a] a single Low Power PD powered
through either pairs AB or pairs CD, [b] a single Medium Power PD
powered
through pair AB or [c] two independent Medium Power PDs, one power
through
pair AB and one powered through pair CD.
2. It is possible that a PD system will get power from N x Ports=RJ45 by
utilizing a PD system that is constructed fron N PDs.
3. item 2 is out of scope of the standard due to the fact that the
standard define what happen in a single port.
I'm not sure I would call this a 'PD system'. I would certainly agree
that
a 'system' could get power through N x RJ45 connectors, each of which
would be a PI, with either 1 or 2 PDs 'behind' each of these PIs. I
would
therefore suggest:
[2] It is possible for a 'system' to be powered through N x PIs with
each
PI supporting either one or two PDs (see item [1] above).
[3] Specification for Item 2 is out of scope as the standards defines
what
happens at a PI which is the conformance test point.
"Yair Darshan" <YairD@xxxxxxxxxxxxxx> wrote on 14/06/2006 13:11:34:
> Hi David,
> I agree with your observation from the RJ45 connector point of view.
> It is actually a basic rule that we are using in the standard i.e. to
> define a port not a system.
> In short you are saying that:
> 1. A single PD in a PoE system can get power from each 2P
> simultaneously.
> 2. It is possible that a PD system will get power from N x Ports=RJ45
by
> utilizing a PD system that is constructed fron N PDs.
> 3. item 2 is out of scope of the standard due to the fact that the
> standard define what happen in a single port.
> I'll revise the presentation accordingly.
> Thanks
> Yair
>
> -----Original Message-----
> From: owner-stds-802-3-poep@xxxxxxxx
> [mailto:owner-stds-802-3-poep@xxxxxxxx] On Behalf Of David Law
> Sent: Wednesday, June 14, 2006 2:17 PM
> To: STDS-802-3-POEP@xxxxxxxxxxxxxxxxx
> Subject: Re: [8023-POEP] System Architecture
> Hi Yair,
> I'm not sure about this idea of N x 2P. The case of 2 x 2P PDs behind
a
> single RJ45 (or 8 pin connector to use the term used in your slides)
is
> certainly a special case we need to look at. But since the RJ45 has
only
> 8-pins you cannot provide any more than 2 x 2P PDs behind a single
RJ45.
> Anything from 3 x 2P upwards requires multiple RJ45s.
> However I would not classify the case of a system with multiple RJ45s
> that
> chooses to implement PDs behind N of these connectors as a case of N x
> 2P.
> This is simply a case of multiple PDs that happen to be located within
> the
> same system. The fact that these multiple PDs happen to be located in
> the
> same system should have no impact on the specification. I would go as
> far
> as to suggest that such system (however system can be defined - within
> same box/chassis/packaging) specifications, certainly in respect to
> Detection and Classification, are beyond the scope of the project.
> There are products that ship today that provide two RJ45 and implement
> two
> PDs behind them to provide redundancy. I believe these are compliant
> with
> Clause 33 of IEEE Std 802.3-2005 and certainly would not agree with
> retrospectively imposing requirements on these.
> Regards,
> David
>
> owner-stds-802-3-poep@xxxxxxxx wrote on 14/06/2006 00:14:40:
> > Hi all,
> > Please find my action item for tomorrow's meeting.
> > It is revised presentation from May meeting that focus on the
concept
> > 4P=2x2P and the more general case of N Pairs = Nx2P..
> > Please feel free to comment.
> > Thanks
> > <<Flexible PD implementation driven Architecture 002.pdf>>
> > Yair
> > Darshan Yair
> > Chief Engineer
> > PowerDsine Ltd. - The Power over Ethernet Pioneers
> > 1 Hanagar St., P.O. Box 7220
> > Neve Ne'eman Industrial Zone
> > Hod Hasharon 45421, Israel
> > Tel: +972-9-775-5100, Cell: +972-54-4893019
> > Fax: +972-9-775-5111
> > E-mail: <mailto:yaird@xxxxxxxxxxxxxx
> > <BLOCKED::blocked::BLOCKED::mailto:yaird@xxxxxxxxxxxxxx> >.
> > <http://www.powerdsine.com
> > <BLOCKED::blocked::BLOCKED::http://www.powerdsine.com/> >
> >
> > [attachment "C.htm" deleted by David Law/GB/3Com]
> > [attachment "Flexible PD implementation driven Architecture 002.pdf"
> > deleted by David Law/GB/3Com]