There are clearly confusions/questions on
the economic feasibility of 40GE 100m objectives. Would appreciate a
presentation to compare the relative cost among the following:
- 4x10G
LAG (10GBASE-SR compliant per lane, possibly 4 x SFP+ or QSFP, whichever
costing lower?)
- 4x10G
LAG (relaxed spec from 10GBASE-SR, but similar to the 40GE per lane basis.
Possibly relaxed spec 4 x SFP+ or QSFP?)
- 40GE
compliant (presumably QSFP?)
- 100GE compliant (SNAP12 TX+RX?)
Wenbin Jiang
From: Dove, Dan
[mailto:dan.dove@HP.COM]
Sent: Thursday, June 28, 2007 8:52
AM
To:
STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [HSSG] The List
Paul,
With regard to the point I made about a
"relaxed spec for 10G" vs writing an "entirely new Ethernet
spec with multiple PMDs for 40G", it was in response to your
contention that 10GBASE-SR would be more expensive to build than one channel of
a new, unwritten, and parametrically relaxed 40G PMD. My point was not that it
is *necessary* to have a relaxed spec for 10G, but rather that if such a
relaxation is to be done, it would be less conflictive with existing projects
to do a 10G PMD than an entire set of PMDs and a 40G MAC spec that lacks
distinction from 100G in the market place. (ie: Two higher speed Ethernets
coming out at the same time with only a slight difference in speed)
It is my firm opinion that we can build
10GBASE-SR compliant SFP+ transceivers and that the total solution cost
compared to X2 or XFP will be significantly lower in cost than today's solution
cost because of the repartitioning of the functionality, the rapidly
diminishing cost of EDC, and the port density improvements which will allow system
vendors to distribute infrastructure cost into more ports than is possible
today.
Dan
From: Paul
Kolesar [mailto:PKOLESAR@SYSTIMAX.COM]
Sent: Wednesday, June 27, 2007
4:40 PM
To:
STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [HSSG] The List
Ali,
there
seems to be a theme throughout your response that implies that cost is
paramount and compliance to 10GBASE-S is of secondary importance. This
subtle but very significant posture may be pervasive with others as well. In
my comparisons I have been holding 10G LAG implementations to the requirements
of 10GBASE-S. Dan suggested that a relaxed spec version of 10GBASE-S
could be an alternative that makes LAG more attractive from a cost perspective.
And I am asking Jack to clarify his statements with respect to
compliance. Now you make similar intonations. While this may be an
alternative, it is one that distorts the reality of the day. We do not
have a relaxed spec, and although it is possible to conceive of such a change,
there is no study group activity in that direction. So it seems mostly
academic at this point because proprietary solutions of this sort do not ensure
interoperability. We need to be very clear on this assumption in our
comparisons going forward.
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
|
"Ali Ghiasi"
<aghiasi@broadcom.com>
06/27/2007 12:33 PM
|
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To
|
"Jack Jewell" <Jack.Jewell@PICOLIGHT.COM>,
"Paul Kolesar" <pkolesar@systimax.com>
|
|
cc
|
STDS-802-3-HSSG@listserv.ieee.org
|
|
Subject
|
Re: [HSSG] The List
|
|
Jack and Paul
The question is not whether SFP+ can achieve 300 m SR reach similar to XFP, but
how do we get to 10G SFP+
at 2.5x the cost of 1G classic SFP for DCE (Data Center Ethernet) with max
reach of 100 m.
If we can get to 10G SFP+ at 2.5x the cost of 1G at 300 m then the 10G PAR
objective is complete, but how long
do we wait the need is know. But I do know the combination of lower cost
optics with EDC can deliver
the 2.5x cost objective for DCE applications near term. To get to these
cost the transmitter very likely
will not be fully SR compliant and in that case it does not matter if the reach
is 100 or 300 m.
The current assumption in the HSSG is that you can achieve SFP+ limiting
performance with 4 or 10 channels without the
use of CDR in the module, with more crosstalk, less optimum layout, SerDes
having more jitter and less tolerance compare
to small port count PHYs, optics ??? You will get small benefit from
reducing fiber reach to 100m but not enough to close the
link budget. As Dan mentioned EDC is becoming an standard feature on PHYs
and we definitely need to leverage it for 40G/100G.
Use of linear interface is an approach that can close the link budget without
the use of CDR in the module, relax the optics
specifications, and the same interface can support passive copper Twin-ax up to
10m.
Ali
Jack Jewell wrote:
Input from a transceiver vendor with experience
and interest in both serial and parallel modules:
First, SFP+ achieves the 300m SR objective with similar ease
as XFP. While a reduced-reach 10G PMD might reduce costs, it's a
retreating approach that requires the customer to purchase higher-cost
transceivers to fill in the reach gap, e.g. for reaches between 100m and 300m..
A reduced operating temperature range offers immediate cost savings for
some customers without compromising reach and without any new standards
specifications. Use of a linear receiver and EDC and relaxed Tx specs can
also achieve the 300m reach at reduced cost. For this application, the
amount of compensation required is far less than what is required for LRM.
EDC is becoming widely available, to the point of being a standard
feature of PHY ICs, so the cost of this EDC is becoming insignificant.
Forward-looking standards efforts will achieve their full impact by
making use of EDC.
For QSFP,. Here again, EDC offers great advantage, and
ignoring it would be a mistake. But crosstalk introduces module-level
limitations that might motivate reach reduction or other modification to the
PMD.
Comparing costs, the SFP+ will be lower than QSFP for the
forseeable future (per lane for the same spec). The only advantage of
QSFP over SFP+ is density and possibly simpler cabling. However, a
12-channel parallel module pair, e.g. SNAP12, offers greater density than QSFP
and 2.5-3X the bandwidth at <2X the cost.
Jack
From: Dove, Dan [mailto:dan.dove@HP.COM]
Sent: Wednesday, June 27, 2007 9:32 AM
To: STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [HSSG] The List
Paul,
Regarding SFP+, I am very familiar with the technology and
have been tracking the SFF-8431 development. The architecture re-distribution
of cost that SFP+ offers will have a substantial impact on cost, especially
when combined with the higher density we can achieve with smaller geometry
ASICs and multiport PHYs that will come with it.
As for QSFP, I am less familiar with whether or not it will
provide a cost improvement over SFP+ or be capable of meeting the existing SR
spec. This is something for the QSFP experts to consider, but like I said, a
shorter 10G PMD might be the avenue to take rather than an identity challenged
40G spec.
Regarding LAG, my conversation with HP Server architects
indicates there are a number of avenues for improvement of LAG under
development.
I cited these areas in my earlier message and would
appreciate them being addressed rather than ignored.
Dan
From: Paul
Kolesar [mailto:PKOLESAR@SYSTIMAX.COM]
Sent: Wednesday, June 27, 2007 8:04 AM
To: STDS-802-3-HSSG@listserv.ieee.org
Subject: Re: [HSSG] The List
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.
Enterprise® Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@commscope.com
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.
Enterprise® Solutions
1300 East Lookout Drive
Richardson, TX 75082
Phone: 972.792.3155
Fax: 972.792.3111
eMail: pkolesar@commscope.com
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