Joel,
1) Thank you for giving me the benefit of the doubt that I wasn’t advocating something silly. It is critical to have roadmaps, project future technology, and put up straw men. This makes discussion specific and substantive rather than generic. While doing that, it is important to keep in mind that we rarely get it right when making projections so should maintain a healthy dose of skepticism about how we use it.
To make our exchange specific, my concern about adopting a 100G Serial architecture now is exactly the same as my concern about adopting 40G Serial in .ba for 40GBASE duplex SMF PMD. It’s too soon.
http://www.ieee802.org/3/ba/public/sep08/cole_02_0908.pdf#page=5
Agreeing that 40G Serial is the right long-term high-volume solution doesn’t mean that it is right when adopted too early. 40G Serial was 15 years too early as 40G OC768 Telecom client, and it would have been 8 years too early if we adopted it as 40Gb/s Ethernet in .ba. 100G Serial will be the right answer >2020. It’s too soon to standardize it now and lock in today’s understanding and technology as the right long term solution.
40G Serial offers another example why we should be cautious. In .ba we thought the ultimate 40G Serial architecture is NRZ. However, we are now considering PAM-4 as a possible alternative, which at the time wasn’t even on anyone’s radar screen as a PMD alternative.
Dave Chalupsky wonderfully qualifies his projections: “Current Forecast … surely accurate J “. Great attitude to have.
2) My view of the right next rate steps after 400Gb/s Ethernet are 1.6T for switches and 800G for servers, but not 1T.
Chris
From: Joel Goergen (jgoergen) [mailto:jgoergen@xxxxxxxxx]
Sent: Monday, July 14, 2014 8:51 AM
To: Chris Cole; STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Chris
I think I am missing what you are getting at. If you can, please clarify.
1) I think I heard you say we should only be standardizing technology within the short term 2 to 4 years. That we should not be long range planning or discussing long range directions. If this is true, I seriously disagree. It implies that we will be short sighted in innovation and ultimately, giving the customers limited technology choices for their applications. Like I said, I don't think this is what you mean.
2) I keep hearing that you do not want 1TbE. What is it that you think we need going into 2018/2020? What is the technology plan and solution set you are offering? I don't believe 400GbE LAG is going to work well. And I believe that if that is the direction you want to go in, that we better start a CFI to address LAG and the efficiency issues related to higher speed ports and associated traffic patterns.
Take care
Joel
From: Chris Cole <chris.cole@xxxxxxxxxxx>
Reply-To: Chris Cole <chris.cole@xxxxxxxxxxx>
Date: Sunday, July 13, 2014 9:51 PM
To: "STDS-802-3-400G@xxxxxxxxxxxxxxxxx" <STDS-802-3-400G@xxxxxxxxxxxxxxxxx>
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Ciao Marco,
When presenting this diagram before, and again later this week, the accompanying remarks are that it is not the objective to claim with any certainty that 100G linear I/O will be the ultimate 100G high volume interface. Just the opposite, the objective is to caution through example about claims that we have sufficient insight to define optimum architecture for >8 years out. A compelling aspect of this example is that it shows an approach to get to ~1W/100G transceiver architecture. This is in contrast to a fully re-timed architecture with internal DAC/ADC/DSP/FEC PHY. Another example of a candidate ultimate architecture is DP-QPSK. A lot of telecom R&D is ongoing in this area which could lead to breakthrough advances in the cost of coherent components. There are other examples of possible technology breakthrough areas.
We should discount arguments in support of standardization proposals which claim to be solving >2020 problems. Our evaluation of PMD alternatives should be based on solving current and next generation problems, using technology that we understand and have experience with. This enables objective decision making, in contrast to debating which technology will and will not arise in the far future.
Separately, I hope we never have to discuss 1Tb Ethernet. We should learn a lesson from the contortions we are going through now because of non-binary rate increase like 2.5x.
Chris
From: Marco Mazzini (mmazzini) [mailto:mmazzini@xxxxxxxxx]
Sent: Saturday, July 12, 2014 12:24 AM
To: Chris Cole; STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: RE: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Hi Chris,
if I look back from history, your flow chart applies to the 10G case: XAUI (X2,Xenpak) [Today] -> Serial retimed 10G (XFP) [Next] -> Linear (SFP+) [Ultimate], but if we try to apply to the 40G case then we should end with a linear 40G interface as Ultimate.
This can be possible, yet a re-timed 40G serial interface seems more feasible today than a linear one (as at this stage I’m not sure if a 25G linear interface should be a simpler/cheaper solution with respect a re-timed one).
If we follow the same concept and apply to current 25G path forward to 100G , then the next step of 1x100G Re-Timed module can become the Ultimate, at same costs (yet less complexity) than a Linear 100G one (while discussing about 1Tb modules on 2020 … ).
Marco
From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Friday, July 11, 2014 10:41 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Jeff
We have at least two contributions for next week making proposals as to which SerDes rate should be matched.
In his presentation, Vipul proposes that we match 100Gb/s SerDes rate:
http://www.ieee802.org/3/bs/public/14_07/bhatt_3bs_01_0714.pdf#page=6
In my presentation, I propose that we match 50Gb/s SerDes rate:
http://www.ieee802.org/3/bs/public/14_07/cole_3bs_02_0714.pdf#page=8
The important point made by Brad in his presentation is that this is an important consideration in selecting a mainstream PMD architecture.
http://www.ieee802.org/3/bs/public/14_07/booth_3bs_01_0714.pdf
Chris
From: Jeffery Maki [mailto:jmaki@xxxxxxxxxxx]
Sent: Friday, July 11, 2014 1:32 PM
To: Chris Cole; STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: RE: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Chris,
What SERDES rate should be the case where no gearbox/mux is needed? That is the question. We need contributions answering this question. I’m sensing the answer depends upon the reach.
Jeff
From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Friday, July 11, 2014 8:29 AM
To: Jeffery Maki; STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: RE: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Jeff
Brad’s insights are exactly on the mark. Mark Nowell pointed out the same thing on the 25G CFI conference call on 6/27/14.
They also in no way conflict with the needs you identify. If we look at 10G, 40G, and 100G, the all followed the same pattern.
First generation required a mux (or gearbox) to match the higher optical rate to the lower existing electrical I/O (ASIC SerDes) rate. The second generation was optimized for cost and volume and matched the optical and electrical rates, and follow on generations require (or will require) reverse mux (or gearbox) to enable legacy optical interfaces to plug into new electrical I/O ports.
Chris
From: Jeffery Maki [mailto:jmaki@xxxxxxxxxxx]
Sent: Friday, July 11, 2014 8:08 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Brad,
I was thinking that you could at least react to the portion of my presentation that you do not think provides the critical perspective to meet the needs of data centers. Indeed, lets refine things into a consensus presentation for September.
Below in yellow, I mark your slide text that implies (says to me) that “cloud needs a new optical PMD for each SERDES rate.”
For electrical interfaces that are N wide and optical interfaces that are M wide, there is only one case for which N=M. When N does not equal M, a gearbox/mux is needed. To avoid them then requires new optical interfaces to be defined so each new value of N can be matched by a new value of M. SERDES and optical lane speeds have to go in lock step; new optical PMD standard for each case.
As you point out (and I did in my presentation in May) the modulation should also likely match. I would update my presentation to say that they do not have to be defined at the same time, that is the electrical and optical lanes of equal speed.
Considering a gearbox as an implementation fix implies only the one generation where the gearbox/mux is not needed is a proper implementation. Here I disagree. Some applications need interoperation over system generation (i.e., form factor generation), especially among systems from competing system companies. Use of gearboxes preserve interoperation among systems of different SERDES generation and especially among systems from competing system companies with different SERDES rates. Here is where you should separate whether you are talking about interconnects that are primarily for the data center versus for router-to-router or router-to-transport. For the data center, you could assert that the system generation (SERDES) rate is well managed for uniformity among the interconnected systems.
Jeff
From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: Thursday, July 10, 2014 10:41 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Jeff,
Your suggestion for going through your presentation and selecting what you got right is not viable for next week's meeting. If you'd like to get a group together to do that filtering, then we could consider that for the September task force meeting.
You'll have to help me understand where I state that cloud needs a new optical PMD for each SERDES rate. It's not like 802.3 hasn't done that in the past, but I don't see where I state that in my presentation.
Thanks,
Brad
On Wed, Jul 9, 2014 at 6:39 PM, Jeffery Maki <jmaki@xxxxxxxxxxx> wrote:
Brad,
In Norfolk, I made such a presentation of the “things the task force might wish to consider when selecting interfaces.” Thus, I think it would help if you highlighted what you think I got correct in my presentation and what you would change in my presentation or add.
I see in your presentation is that cloud needs a new optical PMD standard for every new SERDES rate. Perhaps you should be discussing how distinct identity is driven by the SERDES rate. Therefore, perhaps we should have multiple optical PMDs defined in the same project aligned to the different SERDES rates.
Jeff
From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: Wednesday, July 09, 2014 12:52 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] [802.3_400G] Presentation for next week
Jeff,
You're correct that answering that question would be great. It's not a simple answer though, and everyone is likely to have varying views. What I was hoping to capture in the presentation is things the task force might wish to consider when selecting interfaces.
I'm hoping that the presentation will permit the task force to discuss some of these issues in a open forum to gain broad consensus on a path forward.
Thanks,
Brad
On Tue, Jul 8, 2014 at 8:01 PM, Jeffery Maki <jmaki@xxxxxxxxxxx> wrote:
Brad,
We have multiple optical reach objectives in 802.3bs. I do not see that the longevity (or obsolescence) would be the same for them all nor that the high-volume market adoption time frame would be the same for them all.
Could you make your presentation more granular with statements per each reach objective?
I don’t like gearboxes or I think you mean to say muxes either but if they do not appear in initial implementations then they will show up sooner as reverse muxes as electrical interfaces progress in lane count reduction. I would presume you would want there to be no mux needed when 400G Ethernet is adopted in large volume in the mega datacenter. The question then is what SERDES rate on switch ASICs do you see 400G Ethernet being adopted in large volume in the mega datacenter?
Jeff
From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: Monday, July 07, 2014 1:13 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: [802.3_400G] Presentation for next week
All,
I'm attaching a first draft of a presentation I plan to make next week at the 802.3bs meeting. If you see any areas where I can provide greater clarification, please feel free to let me know.
If you'd like to be listed as a supporter of this material, I'd be honored to add your name.
Thanks,
Brad