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Re: [HSSG] 40G MAC Rate Discussion

How did this thread get started?


I do not understand the point of comparing a PHYless MSA with a copper PHY.  From a systems perspective, if you are going to compare power budgets, you need to count all the ICs that make the connection work, not just the optical PMD.


If you want the lowest power, plug a copper cable into an SFI interface.




Bruce Tolley

Vice President, Marketing

Solarflare Communications

9501 Jeronimo Road,Suite 250

Irvine, California 92618

ip phone 949 581 6830 X2014

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From: Schube, Scott A [mailto:scott.a.schube@INTEL.COM]
Sent: Tuesday, April 10, 2007 4:03 PM
Subject: Re: [HSSG] 40G MAC Rate Discussion


To add to Paul’s comments I’ll put some actual power dissipation numbers next to this for perspective.  I believe existing 10GBASE-T solutions are in the neighborhood of 10 W, with newer implementations going down to 5-6 W.  Someone from the 10GBASE-T community can correct me if I’ve got it wrong, as I’m not an expert in this area.  So moving to ~25W in the near future for 4 10GBASE-T ports.  This is compared with a 40G QSFP at 3.5W or 4 SFP+ modules at 1W apiece.


So at least for the next couple of years, the big factor in power dissipation for a 4x10G LAG vs. 40G solution would likely be whether it’s done in copper or fiber, not whether it’s a 4x10 LAG or 40G solution.  Where the power dissipation numbers go from there, like Paul said, depends on a lot of factors and is up for (no doubt spirited) debate.




>>Scott Schube

>>Strategic Marketing Manager

>>Intel Optical Platform Division

>>(510) 578-5815


From: Paul Kolesar [mailto:PKOLESAR@SYSTIMAX.COM]
Sent: Tuesday, April 10, 2007 3:45 PM
Subject: Re: [HSSG] 40G MAC Rate Discussion


First, let me apologize for misspelling Scott Kipp's last name in my previous note. Sorry Scott.

I think you have touched on the key issue facing 10GBASE-T: power dissipation.  While we can look forward to lower power consumption with future IC feature reductions, these will be muted by the need for multiple 10GBASE-T PMDs in a LAG or other parallel scenario.  Such power reductions will also enable lower power consumption by the optical PMDs, although by relatively smaller power reduction ratios.  In my estimation it will be difficult, or far into the future, to deliver a 4x 10GBASE-T device that dissipates the equivalent dissipation of 40G parallel optical transceivers.  

The cost of the copper cabling will also be 4x higher than for a single 10GBASE-T link.  So here it would loose its most of its competitive edge.  

The relative PMD cost factors are unknown, since I am not aware of 10GBASE-T ports in the market at this time.  But it is very likely that once 10GBASE-T become highly integrated, they will compete with the parallel optical transceivers where their application spaces overlap.  It is unclear if that overlap will include 40G applications, since LAG deployments will fade as the single PMD solutions become available.

Time appears to be one of the variables with the greatest influence on the optimal choice.  Will that play best to copper or fiber?  Somebody with a better crystal ball than mine on the issues outlined above needs to weigh in.  

Paul Kolesar
CommScope Inc.
Enterprise® Solutions
1300 East Lookout Drive
Richardson, TX 75082

Phone:  972.792.3155
Fax:      972.792.3111

Mikael Abrahamsson <swmike@SWM.PP.SE>

04/10/2007 03:04 PM

Please respond to
Mikael Abrahamsson <swmike@SWM.PP.SE>





Re: [HSSG] 40G MAC Rate Discussion




On Tue, 10 Apr 2007, Ali Ghiasi wrote:

> I know there is readily available solution based on QSFP that could do
> 40G copper with twin-ax cables.  Copper solution are very attractive for
> sub-10m as they offer order of magnitude cost advantage.  Longer reach
> cable not as attractive as you have to use heavier gage which increase
> the cable size, weight, cost, and the complexity of receiver increases.

Well, my idea was to compare 4*10GE LAG and whatever 40GE solution is
being proposed. I understand now I should have written this outright,

My thoughts were that operational cost and CAPEX of doing 4*10GE LAG using
10GBASE-T for servers would be quite a lot lower than any new proposed
40GE solution, since I only saw coaxial and fiber proposed for 40GE
physical media.

Or have I misunderstood 10GBASE-T when it comes to power and reach (100M
over CAT7 or ~50 on CAT6)? Does it require a lot more power than fiber
based solution?

From a pure end-user perspective CAT6-7 based cabling has the lowest
operational cost (physical only) since it's abundant and there is a lot of
experience with that kind of cabling. But perhaps it uses a lot more power
than the other proposed solutions for 40GE?

Mikael Abrahamsson    email: