Dan,
I can't tell how successfully
SFP+ and QSFP will be at meeting the existing 10GBASE-S spec. If
they can, a new shorter distance 10G PMD would not be of value. If
they can't, then a new PMD spec may be worth while. Those attempting
to implement these lower cost platforms need to weigh in to provide guidance.
In the event that either the QSFP and/or SFP+ can meet 10GBASE-S
specs in multiple vendor's platforms, or that a new shorter distance spec
is developed that allows lower cost, the performance issues of LAG will
remain. I believe Howard's presentations on LAG have indicated that
improving LAG would not be without compromise, leading me to conclude that,
however improved, LAG performance could not become equivalent to a 40G
pipe. Developing a 40G spec would ensure a solution that simultaneously
addresses these cost and performance issues.
Regards,
Paul Kolesar
CommScope Inc.
EnterpriseŽ Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@commscope.com
"Dove, Dan" <dan.dove@HP.COM>
06/26/2007 09:24 PM
Please respond to
"Dove, Dan" <dan.dove@HP.COM>
To
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Subject
Re: [HSSG] The List
Hi Paul,
Good points. I was not really expecting to see a significant cost differential
at the PMD although its a good argument that a 100m PMD would be less expensive.
If this is the case, why not do another 10G PMD focused on lowering the
cost of server interconnect? I believe that would be a smaller project
and have a much less significant impact on 100G development.
Thanks,
Dan
From: Paul Kolesar [mailto:PKOLESAR@SYSTIMAX.COM]
Sent: Tuesday, June 26, 2007 6:16 PM
To: STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [HSSG] The List
Dan,
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.
Regards,
Paul Kolesar
CommScope Inc.
EnterpriseŽ Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@commscope.com
"Dove, Dan" <dan.dove@HP.COM>
06/26/2007 02:45 PM
Please respond to
"Dove, Dan" <dan.dove@HP.COM>
To
STDS-802-3-HSSG@listserv.ieee.org
cc
Subject
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 July meeting.
Respectfully,
Dan Dove
Dove Networking Solutions - Serving ProCurve Networking by HP