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

[Valerie Maguire <Valerie_Maguire@xxxxxxxxxx>]

Dear Goran:

Thanks for the clarification.  We
are not talking about the same thing...  I'm talking about a cord
that would accommodate connecting a T568A wired jack to a T568B wired jack
in the same channel (e.g. swaps the position of the "split" pairs)
and you are describing something that is more of a breakout that would
connect one 4-pair cable to two 2-pair applications (possibly) or a custom
application.  See pinout below...

Pin assignment Val’s Crossover Cord			Pin Assignment Goran’s Crossover Cord
1	->	3	1	->	3
2	->	6	2	->	6
3	->	1	3	->	1
6	->	2	6	->	2
4	->	4	4	->	7
5	->	5	5	->	8
7	->	7	7	->	4
8	->	8	8	->	5

In my opinion, "Val's Crossover Cord" would have no negative
implications with respect to support of remote powering applications, while
the use of "Goran's Crossover Cord" would be problematic.  Both
cords are allowed by TIA Standards, but I would be curious to know the
actual prevalence of "Goran's Crossover Cord".  I would
expect that they're not encountered in the commercial space very often.

All the best - Val



From:      
 "Hauer, Goran
(Goran)" <ghauer@xxxxxxxxx>
To:      
 "Valerie_Maguire@xxxxxxxxxx"
<Valerie_Maguire@xxxxxxxxxx>, "STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx"
<STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx>, 
Date:      
 02/05/2014 08:50 AM
Subject:    
   SV: [802.3_4PPOE]
Are diode bridges really needed (2).pptx

---

Hi folks
 
It would be a cable made
for as the attached specification as an example. I.e. with the RX and TX
pairs swapped and also the two other pairs swapped.
 
I don't think the T568A and
T568B was intended to provide a recipe for crossover cables, but rather
to incorporate older color wiring schemes.
For 10BASE-T and 100BASE-T
it simply works to wire T568A in one end and T568B on the other as only
the two swapped pairs are used.
 
Best regards,
/Goran
 
Från: Valerie Maguire [mailto:Valerie_Maguire@xxxxxxxxxx]
Skickat: den 5 februari 2014 16:21
Till: STDS-802-3-4PPOE@xxxxxxxxxxxxxxxxx
Ämne: 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.
  [attachment "10x8-33xxx.pdf"
deleted by Valerie Maguire/The Siemon Company]