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Re: [802.3BA] Longer OM3 Reach Objective


Petar,
if all we were trying to do was provide connectivity between servers and access switches, or between nodes of a super computer, I would agree that a 100 m reach is sufficient.  However, the data center environment houses other applications that span significantly larger extents.  Access-to-distribution and distribution-to-core channels extend to 250m or more.  Major clients have used, and continue to use, the 300m reach of 10GBASE-S as their limiting case and therefore have employed topologies that span across pods/zones/quadrants (i.e. major regions of a large data center) interconnected by passive central cross connect facilities.  Such customers will not find a 100m reach sufficient.  

I agree that we should examine the cost-reach trade-off space.  If the percentage PMD cost increase is less than the percentage coverage increase, it is an indication that the trade-off is clearly favoring a single PMD solution with higher reach capability.  If the trade-off is not well balanced, it is an indication that we need a lowest-cost approach to deliver up to 100m, and a longer-reach alternative to address the 250m to 300m channels at a cost that is still attractive compared to SM alternatives.  

Regards,
Paul Kolesar
CommScope Inc.
Enterprise Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone:  972.792.3155
Fax:      972.792.3111
eMail:   pkolesar@commscope.com


Petar Pepeljugoski <petarp@US.IBM.COM>

03/14/2008 09:20 PM
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Re: [802.3BA] Longer OM3 Reach Objective






Frank,

You are missing my point. Even the best case stat, no matter how you twist it in your favor, is based on distances from yesterday. New servers are much smaller, require shorter interconnect distances. I wish you could come to see the room where current #8  on the top500 list of supercomputers is (Rpeak 114 GFlops), maybe you'll understand then.

Instead of trying to design something that uses more power and goes unnecessarilly longer distances, we should focus our effort towards designing energy efficient, small footprint,  cost effective modules.

Regards,

Petar Pepeljugoski
IBM Research
P.O.Box 218 (mail)
1101 Kitchawan Road, Rte. 134 (shipping)
Yorktown Heights, NY 10598

e-mail: petarp@us.ibm.com
phone: (914)-945-3761
fax:        (914)-945-4134
Frank Chang <ychang@VITESSE.COM>

03/14/2008 09:23 PM
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Re: [802.3BA] Longer OM3 Reach Objective







Petar;
 
Depending on the sources of link statistics, 100m OM3 reach objective actually covers from 70% to 90% of the links, so we are talking about that 100m isnot even close to 95% coverage.    
 
Regards
Frank
From: Petar Pepeljugoski [mailto:petarp@US.IBM.COM]
Sent: Friday, March 14, 2008 5:09 PM
To: STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [802.3BA] Longer OM3 Reach Objective

Hello Jonathan,

While I am sympathetic with your view of the objectives, I disagree and oppose changing the current reach objective of 100m over OM3 fiber.

From my previous standards experience, I believe that all the difficulties arise in the last 0.5 dB or 1dB of the power budget (as well as jitter budget). It is worthwhile to ask module vendors how much would their yield improve if they are given 0.5 or 1 dB. It is responsible for most yield hits, making products much more expensive.
I believe that selecting specifications that penalize 95% of the customers to benefit 5% is a wrong design point.

You make another point - that larger data centers have higher bandwidth needs. While it is true that the bandwidth needs increase, you fail to mention is that the distance needs today are less than on previous server generations, since the processing power today is much more densely packed than before.

I believe that 100m is more than sufficient to address our customers' needs.  

Sincerely.

Petar Pepeljugoski
IBM Research
P.O.Box 218 (mail)
1101 Kitchawan Road, Rte. 134 (shipping)
Yorktown Heights, NY 10598

e-mail: petarp@us.ibm.com
phone: (914)-945-3761
fax:        (914)-945-4134
Jonathan Jew <jew@j-and-m.com>

03/14/2008 01:32 PM
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[802.3BA] Longer OM3 Reach Objective



I am a consultant with over 25 years experience in data  center
infrastructure design and data center relocations including in excess of 50
data centers totaling 2 million+ sq ft.  I am currently engaged in data
center projects for one of the two top credit card processing firms and one
of the two top computer manufacturers.

I'm concerned about the 100m OM3 reach objective, as it does not cover an
adequate number (>95%) of backbone (access-to-distribution and
distribution-to-core switch) channels for most of my clients' data centers.

Based on a review of my current and past projects, I expect that a 150m or
larger reach objective would be more suitable.  It appears that some of the
data presented by others to the task force, such as Alan Flatman's Data
Centre Link Survey supports my impression.

There is a pretty strong correlation between the size of my clients' data
centers and the early adoption of new technologies such as higher speed LAN
connectivity.   It also stands to reason that larger data centers have
higher bandwidth needs, particularly at the network core.

I strongly encourage you to consider a longer OM3 reach objective than 100m.

Jonathan Jew
President
J&M Consultants, Inc
jew@j-and-m.com

co-chair BICSI data center standards committee
vice-chair TIA TR-42.6 telecom administration subcommittee
vice-chair TIA TR-42.1.1 data center working group (during development of
TIA-942)
USTAG representative to ISO/IEC JTC 1 SC25 WG3 data center standard adhoc