thanks for your detailed thoughts and
proposals. I appreciate the points you made regarding the volume
effect of 10G components on the cost comparison. The presentation
I submitted for the May interim looked at the intrinsic cost factors and
did not attempt to include volume in the equation. But volume certainly
can be a significant factor. Your suggestion to look into its impact
when comparing 4x10G LAG to 40G is reasonable, but complicated at the PMD
level. As my May presentation shows there are a few ways to implement
LAG on MMF. One uses the XFP, another the SFP+, still another the
QSFP. Today the XFP is shipping to the 10GBASE-S spec, and supports
300m transmission. Designs using SFP+ and QSFP will be more challenged
to meet this spec due to jitter, so it remains to be seen how successfully
these lower cost form factors can substitute for the XFP in 10GBASE-S compliant
LAG. However, a reduced distance requirement, such as that stated
in the HSSG objectives, would greatly improve the chances that QSFP will
suffice for "40GBASE-S". So while volume is important,
these unanswered questions on suitability make it impossible from my vantage
point to determine how the volumes for 10GBASE-S will be divided among
XFP, SFP+, and QSFP. And the effects of volume on production costs
are better left to those who manufacture the devices. Perhaps individuals
with such insights will offer some scenarios.
1300 East Lookout Drive
Richardson, TX 75082
"Dove, Dan" <dan.dove@HP.COM>
06/26/2007 02:45 PM
Please respond to
"Dove, Dan" <dan.dove@HP.COM>
Re: [HSSG] The List
My fellow colleagues ,
Last week I sent out a list of items that
I felt need to be addressed to ensure that a 40G PAR would be justified.
At a subsequent EA teleconference intended to build concensus in the HSSG,
I offered to review the presentations made in support of 40G Economic Feasibility
and comparing 40G vs 4x10 LAG performance to ensure that I was not being
too harsh in my consideration of the material that was presented.
Over the weekend, I reviewed every presentation
I could find on these subjects so that I could be comfortable that I was
not being unfair in my concerns. Fortunately, it was not a huge task as
there are not that many to review.
After doing so, I found myself less
convinced in the validity of some presentations that were made. This statement
is not made to criticize my colleagues, but to honor the concept of peer
review which requires that we review and criticize, otherwise we might
as well just upload them to a server and forget about them.
Specifically, I disagreed with cost arguments
made on the assumption that 10G cost remains a constant, when in fact I
anticipate substantial reductions in 10G cost over the next few years at
a rate much faster than today due to a few factors;
1) Higher density/lower cost optical form
factors (SFP+) allowing better utilization of switch infrastructural cost
and QSFP for NICs.
2) Smaller geometry CMOS allowing higher
port densities to work in synergy with PMD cost reductions.
3) Integration of XFI / SFI interfaces directly
into ASICs or multi-port PHYs driving 10G cost further downward.
4) Higher volumes / commoditization of 10G
driving cost down much faster than the current trajectory.
While 40G can leverage some of these elements,
it cannot leverage the volume that feeds the downward cost spiral. So in
4 years, a 40G switch port cost is going to be based on low-volume, freshly
designed and un-amortized silicon used primarily for server interconnect,
whereas a 10G port cost will be based on amortized, high-volume silicon
being used in a huge array of applications. Having different trajectories,
the relative cost for 40G will be higher than presented. This is true for
100G as well, but who is arguing a need for 100G based on cost? It is bandwidth
that drives 100G demand.
In addition, I found presentations claiming
that LAG was insufficient to address server I/O bandwidth needs, yet those
presentations failed to address upcoming technology enhancements like TRILL
and its impact combined with I/O Virtualization, perhaps with a physical
manifestation of QSFP and MPO optics which I believe can lead to graceful
performance scaling for servers that does not demand an intermediate IEEE
standard. In other words, activities and technologies are advancing which
will parse server network access into multiple conversations that can then
be put onto a LAG group with much higher than presented performance levels.
Now, I realize that I am swimming upstream
here by asking that the proponents for "40G now" to complete
a task that took the 100G proponents almost a year to accomplish, in less
than 6 months, but then I am not asking them to do that. My first choice,
the one I proposed in Geneva, was that we move 100G forward (because it
is DONE) and that we continue to work on 40G (until it is done).
This appears to be a minority position because
apparently some people will accept an unproven 40G proposal rather than
risk 100G. Others think that 40G is proven sufficiently and are demanding
"40G now" or they will not allow a 100G PAR to go forward. Those
in the latter camp must either be unconvinced of my concerns, or they think
my concerns are insufficient to justify any further work being done to
justify a 40G project.
I can accept differences of opinion.
What I cannot do, however, is pretend that
these issues do not exist, or that the work we would have to spend getting
a 40G standard done is not going to delay the much needed 100G aggregation
solution our customers demand. I cannot ignore what I perceive as holes
in the 40G presentations.
So, to provide a little more direction to
my colleagues in the "40G now or the HSSG stalls" crowd, I am
asking you to include relative cost trajectories in your analysis of 40G
vs 10G cost models, and to include technology enhancements to LAG (TRILL,
I/O Virtualization, QSFP, MPO) in your performance analysis.
If you feel that this is unnecessary, I am
requesting that you communicate this position to me as soon as possible
so that I can prepare a presentation on these areas of concern for the
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