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Re: [HSSG] The List


Wenbin,
my presentation from May, kolesar_01_0507, addresses my views on the intrinsic costs of items 1, 3, and 4 of your list.  Regarding item 2, I do not know how to factor in the costs of reduced performance specs on SFP+, since that gets too subtle.  To me the issue was not if there could be cost reductions for SFP+ PMDs but rather if SFP+ systems were capable of 10GBASE-S performance.  There have been statements that SFP+ meets 10GBASE-S specs which imply that its cost improvements relative to XFP do not bring with them significant performance impairments.  If this is true for a broad set of suppliers and systems, then there may be little benefit in a reduced performance 10GBASE-S spec.  Also the cost savings of a reduced performance spec would be quite dependent upon which parameters are relaxed and would likely be quite vendor-specific.  So we may end up with little added clarity in pursuing item 2.  

In the pursuit of clarity, I have asked for criticism of kolesar_01_0507 and for disclosure on the impact of volume assumptions on others' relative cost claims between 4xSFP+ and QSFP.  I hope that through these additional inputs a sufficiently complete picture emerges of the costs of the available alternatives.  I see these specific issues as better communicated through discussion on the reflector than by presentation at the meeting.  But I am open to either approach.  The latter at least has the benefit of being counted as a contribution, although I think reflector threads should also be included in such counts.  

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


Wenbin Jiang <Wenbin.Jiang@JDSU.COM>

06/28/2007 01:54 PM
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Wenbin Jiang <Wenbin.Jiang@JDSU.COM>
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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:
1.        4x10G LAG (10GBASE-SR compliant per lane, possibly 4 x SFP+ or QSFP, whichever costing lower?)
2.        4x10G LAG (relaxed spec from 10GBASE-SR, but similar to the 40GE per lane basis. Possibly relaxed spec 4 x SFP+ or QSFP?)
3.        40GE compliant (presumably QSFP?)
4.        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.
EnterpriseŽ 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


To
"Jack Jewell" <Jack.Jewell@PICOLIGHT.COM>, "Paul Kolesar" <pkolesar@systimax.com>
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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.
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


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"Dove, Dan" <dan.dove@HP.COM>

 


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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>

 


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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