Okay Petar – thanks for clarifying
this.
Jugnu
From: Petar
Pepeljugoski [mailto:petarp@xxxxxxxxxx]
Sent: Tuesday, August 29, 2006
10:55 AM
To: OJHA,JUGNU
Cc:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] BER Objective
Jugnu,
In
HPC where you have thousands of links, if you have to retransmit 1 sec it would
severely impact performance.
Regards,
Petar Pepeljugoski
IBM Research
P.O.Box 218
(mail)
1101 Kitchawan Road,
Rte. 134 (shipping)
Yorktown Heights, NY 10598
e-mail: petarp@xxxxxxxxxx
phone: (914)-945-3761
fax: (914)-945-4134
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"OJHA,JUGNU"
<jugnu.ojha@xxxxxxxxxxxxx>
08/29/2006 01:50 PM
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Please
respond to
"OJHA,JUGNU" <jugnu.ojha@xxxxxxxxxxxxx>
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Re: [HSSG] BER Objective
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Petar,
Can you give us some idea as to how it would impact system
performance? Presumably, all systems have to have some sort of
error-handling mechanism (retransmission, etc.). How “bad” is
it for performance if there is one error in 1 second rather than one in 100
seconds?
Thanks,
Jugnu
From: Petar
Pepeljugoski [mailto:petarp@xxxxxxxxxx]
Sent: Tuesday, August 29, 2006 10:48 AM
To: OJHA,JUGNU
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: RE: [HSSG] BER Objective
Jugnu,
This may work for some applications. I am not sure if it would be acceptable
for Data Center/ HPC.
Regards,
Petar Pepeljugoski
IBM Research
P.O.Box 218
(mail)
1101 Kitchawan Road,
Rte. 134 (shipping)
Yorktown Heights, NY 10598
e-mail: petarp@xxxxxxxxxx
phone: (914)-945-3761
fax: (914)-945-4134
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"OJHA,JUGNU"
<jugnu.ojha@xxxxxxxxxxxxx>
08/29/2006 01:37 PM
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Petar Pepeljugoski/Watson/IBM@IBMUS,
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All of this raises the following question: If this is so hard to measure,
how much impact can it really have in the real world? Why not back the
BER requirement off to 10e-10?
Regards,
Jugnu
From: Petar Pepeljugoski [mailto:petarp@xxxxxxxxxx]
Sent: Monday, August 28, 2006 8:03 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] BER Objective
I agree with Howard. It is impractical and expensive to test for very low BERs
- the specs should be such that the power budget is capable of achieving BER
=1e-15, yet the testing can be some kind of accelerated BER at lower value that
is derived from the curve interpolation.
However, the as with any extrapolation of testing results one has to be
careful, so in this case it will be manufacturers' responsibility to guarantee
the BER=1e-15.
Regards,
Petar Pepeljugoski
IBM Research
P.O.Box 218
(mail)
1101 Kitchawan Road,
Rte. 134 (shipping)
Yorktown Heights, NY 10598
e-mail: petarp@xxxxxxxxxx
phone: (914)-945-3761
fax: (914)-945-4134
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Howard Frazier
<hfrazier@xxxxxxxxxxxx>
08/28/2006 05:39 PM
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Howard Frazier <hfrazier@xxxxxxxxxxxx>
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For the 100 Mbps EFM fiber optic links (100BASE-LX10 and 100BASE-BX10)
we specified a BER requirement of 1E-12, consistent with the BER requirement
for gigabit links. We recognized that this would be impractical to test in a
production environment, so we defined a means to extrapolate a BER of 1E-12
by testing to a BER of 1E-10 with an additional 1 dB of attenuation. See
58.3.2 and 58.4.2.
Howard Frazier
Broadcom Corporation
From: Roger Merel [mailto:roger@xxxxxxxxxxx]
Sent: Monday, August 28, 2006 1:54 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] BER Objective
David,
Prior to 10G, the BER standard (for optical communications) was set at 1E-10
(155M-2.5G). At 10G, the BER standard was revised to 1E-12. For
unamplified links, the difference between 1E-12 and 1E-15 is only a difference
of 1dB in power delivered to the PD. However, the larger issue is one of
margin and testability (as the duration required to reliably verify 1E-15 for
10G is impractical as a factory test on every unit) especially since we’d
want to spec worst case product distribution at worst case path loss
(cable+connector loss) and at EOL with margin. Thus in reality, all
products ship at BOL from the factory with a BER of 1E-15 and in fact nearly
all will continue to deliver 1E-15 for their entire life under their actual
operating conditions and with their actual cable losses.
Thus, if by “design target”, you mean a worst case-worst case with
margin to be assured at EOL on every factory unit, then this is overkill.
I might be willing to entertain a 1E-13 BER as this would imply that same
number of errors per second (on an absolute basis; irrespective of the number
of bits being passed; this takes the same time in the factory as verifying
1E-12 at 10G although this is in fact a real cost burden which adversely
product economics); however, this would not substantially change the reality of
the link budget. It would make for a sensible policy for the continued
future of bit error rate specs (should their be future
“Still-Higher-Speed” SG’s).
-Roger
From: Martin, David (CAR:Q840)
Sent: Friday, August 25, 2006 12:22 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: BER Objective
During the discussion on Reach Objectives there didn’t appear to be any
mention of corresponding BER.
Recall the comments from the floor during the July meeting CFI, regarding how
10GigE has been used more as infrastructure rather than as typical end user
NICs. And that the application expectation for 100GigE would be similar.
Based on that view, I’d suggest a BER design target of (at least) 1E-15.
That has been the defacto expectation from most carriers since the introduction
of OC-192 systems.
The need for strong FEC (e.g., G.709 RS), lighter FEC (e.g., BCH-3), or none at
all would then depend on various factors, like the optical technology chosen
for each of the target link lengths.
...Dave
David
W. Martin
Nortel Networks
dwmartin@xxxxxxxxxx
+1 613 765 2901 (esn 395)
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