Re: [802.3BA] Longer OM3 Reach Objective
Just to clarify, are we discussing an extension of the
OM3 reach objective for both 40G and 100G applications?
Some of the PMD related comments appear to imply that
this would only apply to 40G standard.
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.
1300 East Lookout Drive
Richardson, TX 75082
03/14/2008 09:20 PM
|Re: [802.3BA] Longer OM3 Reach
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.
1101 Kitchawan Road, Rte. 134 (shipping)
Yorktown Heights, NY
03/14/2008 09:23 PM
|Re: [802.3BA] Longer OM3 Reach
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%
From: Petar Pepeljugoski
Sent: Friday, March 14, 2008 5:09
[802.3BA] Longer OM3 Reach Objective
While I am sympathetic with your view of the objectives, I
disagree and oppose changing the current reach objective of 100m over OM3
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
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.
P.O.Box 218 (mail)
Kitchawan Road, Rte. 134 (shipping)
Yorktown Heights, NY 10598
03/14/2008 01:32 PM
|[802.3BA] Longer OM3 Reach
I am a consultant with over 25 years experience in data
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.
about the 100m OM3 reach objective, as it does not cover an
(>95%) of backbone (access-to-distribution and
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
objective would be more suitable. It appears that some of the
presented by others to the task force, such as Alan Flatman's Data
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.
co-chair BICSI data center standards
vice-chair TIA TR-42.6 telecom administration
vice-chair TIA TR-42.1.1 data center working group (during
USTAG representative to ISO/IEC JTC 1 SC25 WG3
data center standard adhoc