Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx



No problem George,

Auto-correction is great but sometimes goes beyond our expectations J

Best regards

Christian

 

From: George Zimmerman [mailto:george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Thursday, February 06, 2014 8:40 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Christian – apologies - please excuse autocorrect mistakes with your name. (very beat red face on my part)

 

George Zimmerman

Principal, CME Consulting

Experts in Advanced PHYsical Communications Technology

george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

310-920-3860

 

(PLEASE NOTE NEW EMAIL ADDRESS.  THE OTHER WILL STILL WORK, BUT PLEASE USE THIS FOR CME BUSINESS)

 

From: George Zimmerman [mailto:george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx]
Sent: Thursday, February 06, 2014 11:38 AM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Christina -

I would confirm what Keng-hua reports, that I know of many PHYs with the crossover correction, on both sets of pairs independently.  I agree that this feature in the PHYs works data-only, and will not effect powering.  However, because of this feature, we therefore do not see any trouble calls from mis-connected crossover cabling.  Therefore we do not seem to have a good way to see whether the two sets of pairs are crossed over independently in the field.

 

One reason that the feature is popular is that the equipment vendor no longer has to worry about the configuration of the wiring (with regards to crossovers).  Specifying a specific configuration for 4-pair POE applications seems to be a step backwards, and would lead us back to the days when the end-user would have to have multiple sets of patch cords handy when connecting a new link so that he could make sure he had the right crossover combination at the end point.  Remember that there are several connections in the link topology where a crossover may or may not occur (either by mistake or by design).

-george

 

 

George Zimmerman

Principal, CME Consulting

Experts in Advanced PHYsical Communications Technology

george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx

310-920-3860

 

(PLEASE NOTE NEW EMAIL ADDRESS.  THE OTHER WILL STILL WORK, BUT PLEASE USE THIS FOR CME BUSINESS)

 

From: Christian BEIA [mailto:christian.beia@xxxxxx]
Sent: Thursday, February 06, 2014 9:13 AM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Thanks Goran, Kenghua,

 

So, if we agree that Auto MDI-X is a data-only feature, and the PoE voltage will not be affected by this feature, I would propose not to mention Auto-MDI-X when talking about PoE since it creates confusion.  

 

The only reason to mention auto MDI-X is to say that this feature makes crossover cables not needed anymore. And I know it is very widely-adopted feature.

 

For a brand new installation, for high power PoE application, we are specifying cabling performance anyway (cable category, bundle size etc..).

So, it seems to me that specifying to use straight cable would be fair as well. It would add no cost, and it would make lose no feature.

   

I’m not trying to get rid of active bridge in application where plug&play and backward compatibility are requested and appreciated feature!

 

I would like to specify a single voltage polarity at new 4PPOE PSE output, so that the new 4PPOE PD would not need diode bridges for high power application (e.g. > 51W)

 

Doing so, there will be no need for designing PSEs with voltage auto-selection as Goran is proposing.

I think this would add extra-cost  and complexity to the PSE, and also could impact system efficiency since extra-switches are needed.

 

Best regards

 

Christian

 

 

 

From: Chuang, Keng Hua (HP Networking) [mailto:kenghua.chuang@xxxxxx]
Sent: Thursday, February 06, 2014 4:00 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Hi,

 

It is data-only feature. The transceiver will cross the data path internally but the physical connection of the power delivery path remain the same.

 

kenghua

 

From: Hauer, Goran (Goran) [mailto:ghauer@xxxxxxxxx]
Sent: Thursday, February 06, 2014 5:44 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: [802.3_4PPOE] SV: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Hi Christian, all,

 

I would assume that it is a data feature only.

 

However, it would be really nice to remove those rectifying bridges from the PD, to both increase efficiency and reduce cost and complexity in the PD.

 

I have taken a look at what could be done at the PSE side.

If you could consider that a 4-pair powered device (PD) would accept power a bit differently from the old PoE standard, by instead powering the pairs 3,6 and 4,5 with the negative voltage and the pairs  1,2 and 7,8 with the positive voltage, the polarity at the PD side wouldn't change regardless of straight cable, "Val's Crossover Cord" or "Goran's Crossover cord".

The PSE would then need to be able to swap polarity between two of the pairs (for instance between pairs 4,5 and 7,8) to maintain compatibility with the old PoE standards.

 

When typing this down, I came to think about that it could maybe be solved even more elegantly by supplying the pair 4,5 with the negative voltage and the pairs  1,2 and 7,8 with the positive voltage regardless, and after identification of the PD type, the PSE would either power the pair 3,6 with positive voltage for an old (2-wire) PoE PD or with negative voltage for a 4-wire PoE PD. The 4-wire PD would then need to be able to connect the pairs 3,6 and 4,5 together in the powered state. It would also need to be able to rectify the voltage on the pairs 3,6 and 4,5 during detection and negotiation (classification). This reduces the total number of needed transistors at the PSE and PD but adds a rectifier (that only need to support detection and negotiation currents) and a switch (transistor) to the PD. This PSE solution would also only support 2-wire powered PoE PD that accepts power on the data pairs.

 

There should be other possible solutions to be able to get rid of those rectifying bridges, I would be happy to see some more brainstorming about this.

 

Best regards,

/Goran

 

Från: Christian BEIA [mailto:christian.beia@xxxxxx]
Skickat: den 6 februari 2014 09:53
Till: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Ämne: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Thanks Peter, all,

 

Let’s consider a PSE switch where those transceivers with Auto-MDI feature are present.  

Would it automatically  adapt the port voltage polarity as well? Or is it a data-only feature?

Thanks,

best regards,

 

Christian

 

 

From: Peter Johnson [mailto:peter_johnson@xxxxxxxxx]
Sent: Wednesday, February 05, 2014 7:14 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

All,

 

It might be telling that there are 10/100/1000 PHY transceivers that automatically adapt to crossover (Auto-MDI) with BOTH the "data" pairs (1,2/3,6) and the "spare" pairs (4,5/7,8) independently.

 

Regards,

Pete Johnson

 

Sifos

 

-------- Original Message --------
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx
From: Christian BEIA <christian.beia@xxxxxx>
Date: Wed, February 05, 2014 10:51 am
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx

Hi Val,

a “4-pair crossover” is a cable which inverts voltage polarity on both 1,2 / 3,6 pairs and  4,5 / 7,8 pairs.

In other words 1,2 pair at one end is connected to 3,4 at the other end, and 4,5 is connected to 7,8.

 

I don’t know if such a cable complies with any standard, but it seems that exists on the market.

 

Goran,

did I understand correctly?

 

Bet regards

Christian

 

 

From: Valerie Maguire [mailto:Valerie_Maguire@xxxxxxxxxx]
Sent: Wednesday, February 05, 2014 4:21 PM
To: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 

Hi Christian:

What is a “4-pair crossover” cable?  Is a modular cord that is wired T568A on one end and T568B on the other?  If so and this cord is used as designed, it would ensure that the same pair combination is "split" (e.g. terminated to pins 4,5 and 3,6) on both ends of the channel.

All the best - Val



From:        Christian BEIA <christian.beia@xxxxxx>
To:        STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx,
Date:        02/05/2014 01:55 AM
Subject:        Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx





Thank you Goran,
I was not aware about this case.
 
Is there anyone who can tell if those “4-pair crossover” cables are standardized or not?
 
Thank you
Best regards
 
Christian
 
 
 
From: Hauer, Goran (Goran) [mailto:ghauer@xxxxxxxxx]
Sent:
Friday, January 31, 2014 4:41 PM
To:
STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Subject:
Re: [802.3_4PPOE] Are diode bridges really needed (2).pptx

 
Hi guys
 
I haven't participated in any meetings live, but I have been subscribing to this list for quite some time. Great work you guys!
 
When I saw this presentation however I must say that I have seen (and used) crossover cables intended for 1000BASE-T that crosses all four pairs, whether they are standardized or not that I can't tell, but they are out there.
 
Best regards,
/Goran
 
Från: Chad Jones (cmjones) [mailto:cmjones@xxxxxxxxx]
Skickat:
den 31 januari 2014 16:14
Till:
STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Ämne:
[802.3_4PPOE] FW: Are diode bridges really needed (2).pptx
 
Christian, the reflector should be able to handle attachments up to 2MB in size.
 
All, I am forwarding this on behalf of Christian. He is looking for some help to decide if we can pursue removal of auto-polarity in the PD.
 
Christian, I am going to forward this to Pat Thaler (I’m not sure that she’s subscribed to our reflector). I will copy you. It was her comment in AF that eventually led to us mandating autoMDIX support.
 
Chad Jones
MGR, HW ENG, Cisco Systems
Chair, IEEE P802.3bt 4PPoE Task Force
 
 
From: Christian BEIA <christian.beia@xxxxxx>
Date:
Friday, January 31, 2014 at 6:02 AM
To:
Yair Darshan <
YDarshan@xxxxxxxxxxxxx>, Fred Schindler <fred@xxxxxxxxxxxxxx>, Dave Dwelley <ddwelley@xxxxxxxxxx>, "Picard, Jean" <jean_picard@xxxxxx>, Chad Jones <cmjones@xxxxxxxxx>
Cc:
"Yseboodt, Lennart (
lennart.yseboodt@xxxxxxxxxxx)" <lennart.yseboodt@xxxxxxxxxxx>, "Abramson, David" <david.abramson@xxxxxx>, "Kousalya Balasubramanian (kousalya.balasubramanian@xxxxxxxxx)" <kousalya.balasubramanian@xxxxxxxxx>
Subject:
Are diode bridges really needed (2).pptx

 
Hi Guys,
I’m trying to find out if having a defined voltage polarity at the PD PI is an achievable goal.
Please look at the short presentation in attachment. It summarizes the spec we have today.
 
After this brief research, my understanding is the following:
 
About Alt-A: reverse polarity at the PD happens only if a MDI-X cable is used and there is no auto-detect mode
About Alt-B: reverse polarity at the PD should never happen.
 
Are those assumption correct?
 
If they are correct, I would like to understand if auto-detect mode is a common feature or it is something “advanced”.
 
I can imagine that a Midspan probably won’t have an auto-detect feature. But what is the reason for using MDI-X cables between the midspan and the PD?
 
Thank you for any comment
 
Best regards
Christian
P.S.
Chad,
I’m not using the reflector since I’m not sure I can attach presentations there.
If it is ok I will forward this email to the reflector.
 


No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.3462 / Virus Database: 3684/7067 - Release Date: 02/06/14