Re: [802.3BA] XR ad hoc Phone Conference Notice
Joel,
Of course the 10km SM PMDs, 40/100GBASE-LR4,
will support the longer distances within the data center. But they
will not do it cost effectively. Instead, they will erect a barrier
to the larger market. There has been no proposal or study of a 1km
SM PMD. I think it is a given that such a solution would not be competitive
against a multimode solution. Just look at LX4 compared to S. As
a result all XR proposals are on multimode fiber because they all leverage
the lowest-cost optical PMD platform.
The concern you express over a surprise
issue, similar to that of DMD during GbE development, is not likely to
appear. Parallel optics on multimode has been used at multi-gigabit
lane rates for many years and deployed in the tens to hundreds of thousands
of channels. Experience in this area has already lead to the handling
of propagation delay skew. We addressed that with the delay skew
model adopted at the last meeting.
Regards,
Paul Kolesar
CommScope Inc.
Enterprise Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@xxxxxxxxxxxxx
| Joel Goergen <joel@xxxxxxxxxxxxxxx>
07/11/2008 12:30 PM
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Paul,
Thanks for the comments ... there is a lot of data to absorb in this thread
:).
In terms of a new objective, why won't the SMF 10km solution target the
space we are discussing? Was there promise somewhere that 100G implementations
would work on all fiber install base? Do we know for certainty that
if we did pursue this objective, that:
1) it would be better served with a 1km SMF objective
2) we would not run into issues like 1G DMD at the end of the project
take care
-joel
Paul Kolesar wrote:
Joel,
in apparent contrast to your perception of my message, you and I are in
agreement. While Corning's customer survey indicates a strong preference
for a single PMD that can reach 150m on OM3 and 250m on OM4, I have stated
that the cost and/or power penalty this would impose leads me to the conclusion
that we need a second PMD to address the reaches between 100 and 250m.
This avoids changing the 100m PMD objective, yet delivers a more
capable solution which can be deployed selectively where needed. It
is also my understanding that these longer reaches are needed to cover
the backbone portions of the data center, which will support traffic aggregated
from lower rate channels. This aggregated traffic represents one
of the primary reasons to deploy higher rate Ethernet. To not provide
a low-cost solution for this space is to ignore one of the earliest applications
that will drive broad market adoption.
To be completely clear, I am advocating retention of the 100m objective
and the development of a longer reach solution.
Regards,
Paul Kolesar
CommScope Inc.
Enterprise Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@xxxxxxxxxxxxx
All,
I'm a bit confused to the survey data provided by Petar, Paul, and Steve.
I don't see the data the way Paul implies it in his email, nor in
Steve's. But I do follow Petar's. Petar's data implies that
X length of 100meters accounts for Y amount of total From a cost
perspective, developing a 100m MMF solution with no CDR, low power, and
reasonable margins gives a great product for more then 85% of the solution
space. Paul's data supports that up to about 90%
So ....why do we want to penalize the 85% to 90% adopters that do not need
or plan to use more then 100m MMF? There appears to be a cost difference
between 100m MMF PMD and 150 to 200m MMF PMD. The difference being
cost of electronics plus cost of fiber ... OM4 as indicated. I have
yet to see a cost analysis that would justify us increasing the cost to
address less then 10% of the implementation space. It makes no sense.
Leave the fiber objective as is and allow industry the time to analyze
cost vs distance objectives in the 2011 time frame. The data should
show what Paul's data indicates ... there is not enough implementation
space to justify the cost increase of the optics module for all adopters
of MMF. The cost needs to be added only to that implementation space
that requires it. Which, I believe is what Petar was indicating.
thanks
-joel
Paul Kolesar wrote:
Steve,
thanks for furthering the discussion. Your views make sense to me.
I'd like to examine the super computer cabling distance distribution that
Petar shared with us yesterday in a bit more detail. I've plotted
it to allow folks to see it in graphical form.
This data has several features that are remarkably similar to that of general
data center cabling.
1) The distribution is highly skewed towards the shorter end of the distribution.
2) The distribution has a very long tail relative to the position of the
mode, the most frequent length, at 20m.
3) The mode is at a distance that is one fifth of the maximum length.
The white dot on the graph represents the coordinate of equivalent coverage
relative to the 100m objective to the data center cabling distribution.
Speaking to Steve's point that questions the correctness of the 100m
objective for HPC environments, I would venture to say that a 25m objective,
which is the roughly equivalent in coverage to the 100m objective we are
attempting to apply to data centers, would not be satisfactory for the
HPC environment, as it would leave a significant portion of the channels
without a low-cost solution.
It is clear that the 100m objective is a near-perfect match to the needs
of HPC. Yet I do not believe that HPC should be the primary focus
of our development. We must be developing a solution that properly
satisfies a much larger market than this or we are wasting our time. Indeed,
given that latency is a major performance concern for HPC, the vendors
of such machines may prefer to use InfiniBand. This could mean that
one of the primary customers to which we have tuned our present objective
will actually not use Ethernet, but will benefit anyway by driving InfiniBand
to adopt the same 100m PMD specs that 802.3ba defines. This possibility
reinforces my perspective that we need to properly address a broader set
of customers - those that operate in the general data center environment.
It is clear from all of the data and surveys that remaining only
with a 100m solution misses the mark for this broader market. Continuing
under this condition will mean that the more attractive solution for links
longer than 100m in the general data center will be to deploy link aggregated
10GBASE-SR. Its cost will be on par and it will reach the distances
the customers need in their data centers.
Is this the future you want for all our efforts, or do you want to face
the facts and address the issue head on with a solution that gives data
center customers what they need?
Next week these decisions will be placed before the Task Force. I
hope we choose wisely.
Regards,
Paul Kolesar
CommScope Inc.
Enterprise Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@xxxxxxxxxxxxx
All,
I think Paul's suggestion is a good one; I would like to add some other
input (in the form of questions) from my point of view:
1. Do we have the right MMF objective (support at least 100m on OM3 fiber)?
My data suggests that we don't; we have tried to come at this from two
different directions, trying to be as unbiased as possible in assessing
the situation. I presented Corning sales data in November 2006 (see http://www.ieee802.org/3/hssg/public/nov06/swanson_01_1106.pdf).
This data showed a need to support a link length longer than 100m and I
recommended that we support 200m at that time.
We also polled our customers, offering three options, a low cost, single
PMD at 100m on OM3, a slightly higher cost single PMD at 150-200m on OM3,
and a third option that would specify two PMDs consisting of both option
1 and option 2. The results were overwhelmingly in favor of Option 2, a
single PMD at longer length. A small number supported Option 3 (2 PMDs)
but NONE supported Option 1. While it is true that many of our customers
have a substantial portion of their link lengths that are less than 100m,
they all have link lengths longer than 100m. One customer noted that more
than half of his data center had link lengths longer than 100m.
Kolesar presented his company's sales data in September 2006 (see http://www.ieee802.org/3/hssg/public/sep06/kolesar_01_0906.pdf).
His data also suggested that longer link lengths were needed and he recommended
150m at that time.
All the data for datacenter seems to suggest that 100m is TOO SHORT to
cover a significant portion of the datacenter application.
Pepeljugoski presented new data yesterday on HPC link lengths that show
85% being less than 20m and 98% less than 50m. This might suggest that
100m is TOO LONG for HPC applications.This leads to another question of
whether there is any economic or technical advantage to a shorter MMF objective
for HPC?
2. Is there consensus on supporting a longer reach objective for MMF?
I think there is, others on the call yesterday did not. I base my opinion
on the straw poll conducted in Munich:
Straw Poll #15: Should we continue to work on a proposal for an annex to
extend the reach of a 40GBASE-SR4 and 100GBASE-SR10 in addition to the
proposal(“pepeljugoski_01_0508.pdf”) as in “jewell_01_0508.pdf”.
Yes: 55
No: 3
3. Could we achieve 75% support
for adding a new MMF objective?
I don't know but if we could not,
I would be forced to vote against adopting the current MMF baseline proposal
(which I don't want to do) and I think others may also. This may or may
not lead to an impasse similar to what we experienced in 802.3ae.
I understand the concern that adding
the objective without a clear consensus on how to support the new objective
could lead to delay but I have found this committee to be very resourceful
in driving to a solution after we have made a decision to go forward. 40G
is one recent example of a situation where no consensus turned very quickly
to consensus.
I think adding a new objective
is the right approach and in the long run will save the task force valuable
development time.
4. Can we agree on the right
assumptions on the 10G model to evaluate the various proposals?
Everyone seems to be using slightly different variations of the model to
evaluate the capability of the proposal; we need to agree on a common approach
of analysis.
5. Can we not let the discussion on OM4 cloud the decision?
We can get extended link lengths on OM3. By achieving longer lengths on
OM3, even longer lengths will be possible on OM4 with the same specification.
What I don't want people to think is that OM4 is required to get longer
lengths.
6. Summary
John D'Ambrosia has provided advice that if we want to move forward with
a new MMF objective, July is the time to do it - if we delay the decision,
it is guaranteed to delay the overall process. Some might think if we make
the decision, it will delay the overall process but we don't know that
yet. I don't think adding an informative specification on a PMD is the
right way to go - let's get the MMF objective(s) right - we owe it to ourselves
and to our customers. To do anything less is just avoiding the issue. Let's
get the objectives set, get the assumptions correct and utilize the process
set up by Petrilla and Barbieri to drive toward the hard decisions that
we are all very capable of making.
Sincerely,
Steve Swanson
From: Paul Kolesar
[mailto:PKOLESAR@xxxxxxxxxxxx]
Sent: Thursday, July 10, 2008 7:19 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Alessandro,
I'd like to continue your thread with some observations that have driven
me to certain conclusions, and to follow that with a suggestion about how
to parse the approach and drive to a consensus position.
First let's consider what various customers are telling us. The Corning
survey of their customers, which has been presented to the Ethernet Alliance,
the XR ad-hoc, and will be presented next week to 802.3ba, shows that the
large majority of customers want a single PMD solution that can provide
150m on OM3 and 250m on OM4. A minority were willing to accept a
two PMD solution set that delivers the lowest cost PMD to serve up to 100
m and a second PMD to serve the extended distances as above. Not
a single response indicated a preference for a solution limited to 100m.
We also hear strongly expressed opinions from various system vendors
that a longer distance solution is not acceptable if it raises cost or
power consumption of the currently adopted 100m PMD. Under these
conditions, and given the options presented and debated within the XR ad-hoc,
I believe you are justified in concluding that a single PMD cannot satisfy
all these constraints. Yet it is clear to me that the market will
demand a low-cost PMD that can support more than 100m to fulfill the distance
needs of data centers. Therefore I conclude that the correct compromise
position is to develop a two-PMD solution. If the committee does
not undertake this development, it is likely that several different proprietary
solutions will be brought to the market, with the net result of higher
overall cost structures.
So let's consider how to choose from among the various proposals for an
extended reach PMD and let the determination of how to document it within
the standard be addressed after that.
I would propose a series of polls at next week's meeting designed to gauge
the preferences of the Task Force. I do not think that any XR proposal
will garner >75% at the outset, so I would propose the use of Chicago
rules wherein members may vote for all the proposals they find acceptable.
From this we can see which of the solutions is least acceptable.
Then through a process of elimination from the bottom, and repeated
application of Chicago rules for the remainder, finally determine the most
acceptable solution.
Depending on the degree of maturity of the specifications or other considerations
for the chosen solution, the Task Force will be better able to determine
how it should be handled within the standard. For example, a proposal
with a maturity on par with the adopted baseline could be put forth under
a new objective without undue concern of becoming a drag on the timeline,
while a proposal of lesser maturity could be placed in an annex without
an additional objective.
Regards,
Paul Kolesar
CommScope Inc.
Enterprise Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@xxxxxxxxxxxxx
Matt,
here is my *personal* read of the situation in the XR ad hoc:
a) I think there could be consensus on supporting XR, as long as we pick
a solution that does not impact the cost structure of the 100m PMD. Because
of that I also don't feel a single PMD is realistic at this point.
a) The trouble however is that there is no consensus (>75%) on any of
the technical proposals. No one proposal has a clear lead over the others.
Of the three options you list below, I think adding an objective for a
ribbon XR PMD could have a major impact on the project schedule, because
it seems we are nowhere near technical consensus. We could drag the discussion
for several TF meetings...I am not sure delaying the project over this
specific topic is worth it.
We can always resort to non-standard solutions to fulfill market requirements
we can't address within IEEE, or come back in the future with another CFI.
At the end of the conference call earlier today I requested that we get
together after hours next week to see if we can accelerate consensus building.
All the data is on the table now, so if we don't show any material progress,
I am not sure we should extend this ad hoc.
Alessandro
From: Matt Traverso
[mailto:matt.traverso@xxxxxxxxx]
Sent: Thursday, July 10, 2008 10:07 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Colleagues,
I feel that we are coming to a situation similar to the impasse at 40G
vs. 100G where different participants call different segments of the networking
industry their customer.
For MMF, I'd like to see an optimized solution at 100m per all of the work
that has been done.
I'd like to understand if folks feel that a different status for the extended
reach
a) Informative
b) Normative
c) New objective
would significantly alter the technically proposed solution from the Ad
Hoc. Opinions?
Chris,
The case of slow market/industry transition from LX4 to LRM is one of the
reasons why I would like to see the industry adopt 40G serial from the
launch. The slow adoption of LRM has primarily been limited by end
customer knowledge of the solution. 40G serial technology is available.
thanks
--matt
Hi Gourgen,
Some numbers might help clarify
what close to 0 means.
For 2008, Lightcounting gives
a shipment number of approximately 30,000 for 10GE-LRM (and for 10GE-LX4
it's about 60,000.) So close to 0 would apply if we were rounding to the
nearest 100K. As an aside, 10GE-LRM supports 220m of MMF, not 300m.
300m of OM3 is supported by
10GE-SR, which Lightcounting gives as approximately 400,000 in 2008, so
that would be close to 0 if we rounding to the nearest 1M.
Another interesting sideline
in looking at these numbers is that 2 years after the 10GE-LRM standard
was adopted in 2006, despite the huge investment being made in 10GE-LRM
development, and despite very little new investment being made in 10GE-LX4,
the 10GE CWDM equivalent (i.e. 10GE-LX4, 4x3G) is chugging along at 2x
the volume of the 10GE Serial solution that was adopted to replace it.
This should put some dim on
hopes that very low cost 40GE Serial technology can be developed from scratch
in two years and ship in volume when the 40GE standard is adopted in 2010.
Chris
From: Gourgen Oganessyan
[mailto:gourgen@xxxxxxxxxxx]
Sent: Wednesday, July 09, 2008 8:02 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Petar,
Well, sadly that's what has
been happening in the 10G world, people are forced to amortize the cost
of 300m reach (LRM), while in reality the number of people who need 300m
is close to 0.
That's why I am strongly in
support of your approach of keeping the 100m objective as primary goal.
Frank, OM4 can add as much cost
as it wants to, the beauty is the added cost goes directly where it's needed,
which is the longer links. Alternatives force higher cost/higher power
consumption on all ports regardless of whether it's needed there or not.
Gourgen Oganessyan
Quellan Inc.
Phone: (630)-802-0574 (cell)
Fax: (630)-364-5724
e-mail: gourgen@xxxxxxxxxxx
From: Petar Pepeljugoski
[mailto:petarp@xxxxxxxxxx]
Sent: Wednesday, July 09, 2008 7:51 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Frank,
If I interpret correctly, you are saying that all users should amortize
the cost of very few who need extended reach.
We need to be careful how we proceed here - we should not repeat the mistakes
of the past if we want successful standard.
Regards,
Peter
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
Hi Jeff;
Thanks for your comment. You missed one critical point that there is cost
increase from OM3 to OM4. If you take ribbon cable cost in perspective,
OM4 option is possibly the largest of the 4 options.
Besides, the use of OM4 requires to tighten TX specs which impact TX yield,
so you are actually compromising the primary goal.
Frank
From: Jeff Maki [mailto:jmaki@xxxxxxxxxxx]
Sent: Wednesday, July 09, 2008 7:02 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] XR ad hoc Phone Conference Notice
Dear MMF XR Ad Hoc Committee Members,
I believe our current objective of "at least 100 meters on OM3 MMF"
should remain as a primary goal, the baseline. Support for any form
of extended reach should be considered only if it does not compromise this
primary goal. A single PMD for all reach objectives is indeed a good
starting premise; however, it should not be paramount. In the following
lists are factors, enhancements, or approaches I would like to put forward
as acceptable and not acceptable for obtaining extended reach.
Not Acceptable:
1. Cost increase for the baseline PMD (optic) in order to obtain greater
than 100-meter reach
2. EDC on the system/host board in any case
3. CDR on the system/host board as part of the baseline solution
4. EDC in the baseline PMD (optic)
5. CDR in the baseline PMD (optic)
Acceptable:
1. Use of OM4 fiber
2. Process maturity that yields longer reach with no cost increase
In summary, we should not burden the baseline solution with cost increases
to meet the needs of an extended-reach solution.
Sincerely,
Jeffery Maki
————————————————
Jeffery J. Maki, Ph.D.
Principal Optical Engineer
Juniper Networks, Inc.
1194 North Mathilda Avenue
Sunnyvale, CA 94089-1206
Voice +1-408-936-8575
FAX +1-408-936-3025
www.juniper.net
jmaki@xxxxxxxxxxx
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