Hi Frank,
Thanks for the response.
1) I am not sure I understand the
assumption that QSFP/CFP will share the ICs except the optics to achieve
different link types. For example, I am pretty sure the 100GBASE-SR10 module
will have different ICs relative to 100GBASE-LR4…. Am I missing
something?
2) There are many ways to implement
the CDR function within the module.
I think I’ve addressed the power and
cost comments in previous emails. I am looking forward to Thursday’s
XR telecon. If we keep this up, we’ll have nothing to talk about J
Best Regards,
Ryan
From: Frank Chang [mailto:ychang@xxxxxxxxxxx]
Sent: September 2, 2008 4:39 PM
To: Ryan Latchman;
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3BA] 802.3ba XR
ad hoc next step concern
Ryan;
In compliment to
Ali’s input, I feel there is assumption that QSFP/CFP modules will try to
share most IC parts except optics. That’s why to question the integration of CDR into FP/DFB DML driver, similar to VCSEL
option.
Additional question is that, to integrate
CDR into modules such as QSFP or CFP, the CDR has to be refclkless, then if we
go into such details, such implementation will limit to only very few vendors.
I donot argue the feasibility of
integrating CDR function into such small form factors theoretically, especially
from performance wise in term of small sized XFP. The issue is no matter
how we try to budget the power/size close to realistic, the combined increase
is still quite sizable after magnified by 4x or 10x.
Also the 5% cost adder looks pretty
aggressively to me when referring to cost-effective QSFP/CFP, thus possibly
make the option beyond practical.
Frank
From: Ryan Latchman
[mailto:Ryan.Latchman@xxxxxxxxxx]
Sent: Tuesday, September 02, 2008 12:26
PM
To:
STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
Hi Ali,
I try to stay away from salty foods J.
Sorry if I didn’t respond to your
other comments. I am not sure where the FP/DFB driver requirement comes
from in relation to XR. Can you provide a little more detail on this?
I also don’t see how integration limits implementation
choices. I am interested in exploring the below comment a little further
though…
Current dual XFP CDR burn 450 mW and I suggested we
assume 50% power reduction or
"225 mW" assuming more advance process for
XLAUI/CAUI CDR
Lets work with 225mW for a dual CDR (with
limiting amplifier functionality in the Rx path since as you stated, this
integration has been around for a long time). How much extra power
consumption do you think it takes to integrate VCSEL driver functionality in
the Tx path? Keep in mind that we already had a Tx driver in the ordinal
dual CDR. The total power consumption for the 40GbE case would be the
following:
40GbE CDR based XR Module Power = 4 *
(225mW + Delta VCSEL Driver) +
Quad
Now compare this total module consumption
to the case without CDRs. For the without CDR case, please take into
account that there is still a need for full
fledge VCSEL driver with input / output buffers, limiting
amplification etc. Let me know if you still have an issue with my
estimate in the spread sheet.
On a separate note, Gourgen, the 10mW you
reference might be associated with the linear interface proposal (as seen in
cell F29). The delta in power consumption I referenced below is
40mW. In the spread sheet we have 80mW per lane delta module power
consumption.
Best Regards,
Ryan
David and Gourgen
I could not just stay silent seeing Ryan aggressive power estimate for dual CDR
which is also included in the
XR spreadsheet, as it does not serve anyone to create unrealizable
expectation. But Ryan response was
"As previously discussed, your comparison with XFP
is flawed" .
I also stated the following in previous email to Ryan:
- Integrating CDR with VCSEL driver is feasible but not with
FP/DFP driver
- Integrating CDR with TIA is very risky and may have
physical restriction
- Integrating CDR with LD driver or TIA will limit implementation
choice
- Integrating Limiting AMP with CDR has been slam dunk for
last 7 years, with our introduction of 1st
LA/CDR for XFP.
- Current dual XFP CDR burn 450 mW and I suggested we assume
50% power reduction or
"225 mW" assuming more advance process for
XLAUI/CAUI CDR.
When you sprinkle salt "CDR" all over your dinner you just can't
swallow anymore and end up just filling up on water!
Thanks,
Ali
David Nelson (
From: Ryan
Latchman [mailto:Ryan.Latchman@xxxxxxxxxx]
Sent: Tuesday, September 02, 2008
9:31 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
Hi David, Gourgen,
Thank you for the response. For XR,
the group already has our opinion on the additional power consumption for CDR
functionality. I am not talking about 4W/10W per each end of cable
assembly.
I can’t give exact power consumption
numbers due to competitive reasons. With respect to further evidence on
the power consumption side, I can tell you that Gennum’s Quad CDR with
Limiting Amplifier IC (test chip results have already been shared for XLAUI and
4x10G SMF presentations) will consume less than 40mW more per channel compared
to stand alone limiting amplifiers used in SFP+. In follow on generations,
this difference will continue to reduce. Similar deltas can be observed
in the transmit direction.
I agree with respect to not spending time
on SFP+, and focusing on 40/100GbE. I am not proposing to make CDRs a
requirement. I am presenting this as an option for achieving XR reach.
Best Regards,
Ryan
From:
Gourgen Oganessyan [mailto:gourgen@xxxxxxxxxxx]
Sent: September 2, 2008 10:50 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
I would agree with David.
Also, we shouldn’t lose the sight of what we’re talking about: not
10G SFP+, but a 40G/100G solution. So if it’s 1W, you’re talking
4W/10W per each end of cable assembly.
Gourgen
From:
David Nelson (
Sent: Tuesday, September 02, 2008
9:20 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
To say the power of an sfp+
with dual cdr is less than 1W is not very helpful, considering
10G sfp+ modules range from under 0.5W to nearly 1W already. If your
module including cdr is substantially below 1W, you would be wise, for the sake
of furthering your company goal of getting a spec written to include a cdr, to
get your company's permission to divulge that information. If the module
power with cdr is close to 1W, as many of us suspect, then for many module
vendors that would represent a substantial increase in module power, and the
requirement to include dual cdr's is not persuasive.
David Nelson, JDSU
From: Ryan Latchman [mailto:Ryan.Latchman@xxxxxxxxxx]
Sent: Tuesday, September 02, 2008
5:58 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
Sorry, I can’t divulge that
information. What I can say is that there is margin with respect to SFP+
1W requirement.
Best Regards,
Ryan
From:
Paul Kolesar [mailto:PKOLESAR@xxxxxxxxxxxx]
Sent: August 31, 2008 8:41 AM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR
ad hoc next step concern
Ryan,
what
is the typical and maximum power dissipation of the SFP+ module with the
integrated CDRs that you show below?
Regards,
Paul Kolesar
|
|
Ali,
As previously discussed, your comparison with XFP is flawed.
The cost and power estimates given for XR assumes CDR integration which
is very feasible. For your reference, below is an example PCB of an SFP+
module with CDRs in both directions (CDR with integrated laser driver in the Tx
direction, CDR with integrated limiting amplifier in Rx direction). The
benefits of this are clear. Systems designers don’t need to worry
about jitter budgets (a topic which has plagued SFP+), and it saves them from
having to put standalone signal conditioners on the line card, saving material
amounts of cost and total system power.
The CDR based solution for achieving extended reach is the
most trivial solution since:
1) It uses a simple host interface (XLAUI / CAUI) which can be
leveraged to achieve all types of 40GbE or 100GbE PMD interconnect
2) XLAUI / CAUI enables lots of design flexibility. Hosts
don’t care that the MMF channel is longer.
3) It is well proven technically.
Sorry I missed the XR call, but I was on a plane at that
time. I look forward to additional discussion on this topic.
Best Regards,
Ryan
From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
Sent: August 29, 2008 3:48 PM
To: Ryan Latchman
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx;
DAWE,PIERS; Booth, Bradley
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Ryan
If you compare the cost difference between XFP and SFP module you will find
more than 50% cost difference.
Adding a CDR to an SMF module will add about 5% to the BOM and about 15% to an
MMF module BOM.
As you know the final cost of the module will increase by greater amount than
the BOM cost increase.
You assumption about integrating CDR in the LA/LD may require to use special
process, may limit availability, may have
technical issue of integrating TIA in to a CDR, or may have physical constrain.
During the XR call yesterday we had discussion how the system cost increase if
the port density is reduced my be the greatest cost
factor.
Thanks,
Ali
Ryan Latchman wrote:
Hi Piers,
When considering the 5% cost adder to the module, take a look
at the delta area of adding CDR functionality to a limiting amplifier or laser
driver. I think you will find the extra area is small, particularly when
you take into account bond pads of the LA/LD. Now take into account the
other components which contribute to the cost of the module (ROSA, TOSA, uC…).
I think you will find that a 5% adder is very realistic.
Best Regards,
Ryan
From: DAWE,PIERS [mailto:piers.dawe@xxxxxxxxxxxxx]
Sent: August 28, 2008 12:15 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Hi Brad,
The 5% sounds unlikely (I would have expected more) and
similarly the 17% (what I've seen of the surveys says that when invited to lay
out equipment anywhere with a 300 m constraint, very few links even go beyond
100 m).
But I'm actually writing to reply to your paragraph about
compliance points. Remember that for Gigabit Ethernet, in 38.5, Table
38-10, the Total Jitter at TP1, TP2, TP3 and TP4 are all normative.
Piers
-----Original
Message-----
From: Brad Booth [mailto:bbooth@xxxxxxxx]
Sent: 28 August 2008 03:55
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Dave,
I agree. A 5% cost adder seems reasonable for a 17%
increase in broad market potential.
I do wonder if part of the problem is the compliance points
TP0, TP1, TP1a, TP4, TP4a and TP5. In past efforts such as 802.3z and
802.3ae, these compliance points have been left up to MSAs and only TP2 and TP3
were of concern. Now the task force is dealing with such issues as
modules and the cost impact of various implementations. IMHO, IEEE 802.3
was trying to avoid writing implementation specifications and was focused on
compliance specifications. Could it be that these compliance points are
causing the task force some heartache because it results in an implementation
specification?
Just food for thought...
Thanks,
Brad
From: Chalupsky, David
[mailto:david.chalupsky@xxxxxxxxx]
Sent: Wednesday, August 27, 2008 8:18 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
The 20% cost premium applies to only one of our proposed XR
alternatives.
According to the alternatives spreadsheet
(Comparisons_xr_01_0708.xls) the CDR option adds only 5% module cost premium
over the base proposal and provides reach of 168m to 251m (across the OM3/4,
one-sided/two-sided matrix).
I’m struggling to keep up with the conversation here
– but I believe that the 5% alternative addresses the same problem as the
20% alternative, right?
On that assumption I will rephrase Dan’s non-rhetorical
question to address a 5% cost adder for 17% increase in coverage:
If I have the choice between:
A) carry two product SKUs: 100m and 150m, with 5% Bill of
Material cost delta on the 150m product; or
B) carry only the 150m product
I would accept option B & use only the 150m module even
though I know that most of my customers will use it at <100m.
By considering only the bill of material of the module we are
missing two aspects of the big picture on cost.
1) Carrying multiple product SKUs through design, validation,
manufacture, customer qualification, customer confusion, etc. adds cost.
Regardless of whether 802.3ba adds a second objective, if the
module supplier base develops two different module solutions for 100 &
150m, then the 100m solution will carry an intangible cost burden and the
desired 0% cost adder for 100m will not be achieved anyway.
2) The module is not the whole solution. The CDR module
solution does not add cost to the host. Thus a 5% increase in module cost
is less than 5% increase in the total cost of the switch plus modules.
I appreciate that the task force is learning from the history
of 10GBASE-SR: that over-specifying the solution had a long term cost impact.
However, we should take away another lesson from 10Gbit:
that providing too many options confuses the customers & slows
adoption.
I strongly urge the task force to provide a single solution
for parallel MMF. I believe that it’s worth a 5% cost adder to the
module to achieve that.
I really have no personal (or commercial) reason to prefer
the CDR option. I’m just looking at the 5% figure in the spreadsheet
& wondering why this isn’t a no-brainer.
Thanks for your time,
Dave Chalupsky
From: Dove, Daniel [mailto:dan.dove@xxxxxx]
Sent: Wednesday, August 27, 2008 4:49 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Hi Mike,
We are pretty close to full circle now. :)
Assuming we make the decision that we want to stick with the
"standard" model at 100m to keep those customers we would lose by
adding cost, does the IEEE standardize a 150m solution or do we let the market
solve that problem on its own?
This is not a rhetorical question, although it might appear
to be.
Can someone provide any insight on the sensitivity of the
market to an additional cost of 20% for every 100m link to satisfy the
additional reach?
If the market is insensitive to cost (on this scale) then
perhaps the additional reach is justified. If the market is going to be
sensitive to that differential cost, then the question falls back to whether
the IEEE wants to do a 150m spec or leave it to a market-defned solution.
Dan
From: Mike Dudek [mailto:Mike.Dudek@xxxxxxxx]
Sent: Wednesday, August 27, 2008 4:22 PM
To: Dove, Daniel; STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3BA] 802.3ba XR ad hoc next step concern
Hi Dan
Of course if we don’t increase the cost of the basic
Grade A model and have a Grade B version of the same part for extra reach with
the Grade B version being loaded with any additional costs of handling two
product codes and any additional testing, then we shouldn’t lose any
customers.
Regards
Mike
Dudek
PMTS
Standards & Technology
JDS
Uniphase
Tel
303 530 3189 x7533.
mike.dudek@xxxxxxxx
From: Dove, Daniel [mailto:dan.dove@xxxxxx]
Sent: Wednesday, August 27, 2008 3:23 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Let me re-state one word of that message.
From: Dove, Daniel
Sent: Wednesday, August 27, 2008 2:00 PM
To: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3BA] 802.3ba XR ad hoc next step concern
Hi Steve,
Yes that helped a lot. I hope the others on the list are not
irritated by my request for repetition of the data.
Given the data, it truly is a challenging issue. I see a 20%
premium for a 17% increase in coverage.
This means the confidence in the numbers is exceptionally
important and assuming they are accurate, a judgement call by the committee on
whether or not a 17% increase in port coverage justifies the 20% increase in
cost.
This is important because if you increase the *COST*
of a solution by 20%, you may decrease the number of customers who are
willing to buy it by more than 20%. Thus, in the overall mix, it might turn out
to satisfy less customers overall.
Its a pretty challenging judgement call IMHO.
Thanks for providing the data.
Dan