Re: [HSSG] 10 x 4 = 40
I disagree with your statement "the 10X jump that Ethernet has
traditionally lived by is outdated".
I believe this is a matter of perspective as to whether we are talking
about a LAN, or an extended I/O platform.
For an extended I/O platform, multiples of 2 or 4 make a lot of sense
because we are typically connecting to a single device or an integrated
array. In that case, incremental speed improvements add value if their
incremental cost is lower than the incremental performance advantage.
For a network, where connectivity extends to a much larger number of
devices and topologically extends to extreme distances in some cases,
the need for an aggregating function is paramount. In such a network,
aggregation in multiples of 2 or 4 make absolutely no sense. One could
argue that aggregating in even larger numbers than 10 might make sense
as well, so 10X appears to be a reasonable balance between the need for
aggregating a large number of devices, and the incremental performance
cost required to achieve it.
From: Scott Kipp [mailto:skipp@BROCADE.COM]
Sent: Monday, May 21, 2007 4:15 AM
Subject: Re: [HSSG] 10 x 4 = 40
Well said and I agree that the goal of 100GBASE-SR10 and 40GBASE-SR4
should be a cost effective solution. We have learned a lot from
10GBase-SR and these investments are just beginning to pay off since
10GE is finally seeing considerable adoption.
Dell'Oro reported that 317,900 10GE ports shipped last year. At the
start of 2006, Dell'Oro predicted that 854,000 would ship in 2006, but
only 37% of those shipped. This was mainly due to high cost with 10GE
selling at 31.2 times the average selling price of Gigabit Ethernet
(1GE) in 2006. At this price, 10GE is only selling about 4 ports for
every 1,000 ports of 1GE. Even by 2010, they only predict 31 ports of
10GE to sell for every 1,000 1GE port. These comparisons are all based
on Dell'Oro numbers from their most recent forecast.
One point I'd like to make is that the 10X jump that Ethernet has
traditionally lived by is outdated. From 10M Ethernet to 1GE, the 10X
jump was needed because networking speeds lagged supporting technologies
(processors, storage and buses). With 10GE (and in a similar manner 10
Gigabit Fibre Channel), Ethernet jumped ahead of the other supporting
technologies and it remains ahead of its time. Most users have not
adopted 10GE with only 525,900 ports shipped worldwide by 2007. While
super users who can afford to come to the standards meetings may want
100GE without seeing a price, the Ethernet community should serve more
users by offering a technology that is more immediate, affordable and
readily available - 40GE. 40GE offers a 4x step from 10GE and could see
wider adoption than 100GE if it comes to market at half the cost.
I doubt that 100GE will be cost effective for a considerable number of
years. I fear that 100GE will be out of the price range of all but the
super users. Even some of the super users who are known for using
commodity technology may shun the technology when the see the price tag.
If 40GE is half the price of 100GE, then I would bet that 3 or 4 times
the number of users could afford it. 40GE could help the adoption of
Ethernet by reaching out to the common customers who can not afford to
come to the HSSG meeting but will buy adequate and cost effective
I look forward to talking to people in Geneva about the next step in
Ethernet. I wonder how many people will be going though. I talked to
several people at the SFP+ meeting last week at Cisco and many said they
couldn't justify the trip to Geneva since they expect 100GE to be such a
small market that is still years away. We could make the HSSG more
relevant by making a quicker and more affordable step to 40GE.
PS. I will be discussing plans to release a 40G QSFP this year. Has
anyone heard of a standards based 100GE PMD coming out this year?
From: John Dallesasse [mailto:John_Dallesasse@EMCORE.COM]
Sent: Wednesday, May 16, 2007 7:46 AM
Subject: Re: [HSSG] 10 x 4 = 40
To reinforce Jack's point, as 10GBASE-SR has matured in the marketplace,
many of the initial yield issues have been resolved through device and
process improvements. The early spectral width issue has been
addressed, both by better understanding on the part of the transceiver
manufacturers regarding how to appropriately set their power/OMA tuning
targets to meet the requirements established by the triple-trade-off
curves, as well as by improvements in VCSEL devices themselves. The
proposed distance target of 100m in the HSSG was motivated by all of the
factors that Jack discussed below, as well as the possibility of looking
into a relaxed encircled flux specification, which might be advantageous
when one considers the coupling requirements for a 10 or 12 element
array as compared to a single device.
Jim made some valid points as well. We need to ensure that we set
specifications that do not significantly increase the cost of test, and
as a result the overall cost of the solution. The goal for
40GBASE-SR4) should be a lower cost per transmitted bit than 10GBASE-SR,
which, as Jack said, is the most cost effective of the 10G PMDs and will
continue to be so.
Re: [HSSG] 10 x 4 = 40
Please respond to
I disagree with some points made. There are multiple 10G VCSEL
suppliers, and at least one of them meets the 10GBASE-SR spec without
undo difficulty and with little to be gained by the proposed spec
relaxation. [Won't mention any names, but it's a company with which I'm
quite familiar!] The CDR in the XFP modules has nothing to do with
over-spec'ing SR, and it resides in LR modules as well. Furthermore,
SFP+ modules operate under the 10GBASE-SR specifications and they will
be very cost-effective. CDR and XAUI chip costs, together with the com
crash, presented a far larger barrier to 10G adoption than SR specs.
Let's be careful in drawing analogies with the 10G experience.
At 100G, it's appropriate to have a shorter reach objective than the 10G
one. The main reason is that the near-certain implementation is 10-12
channel parallel optical using fiber ribbon. Issues such as crosstalk,
power variation, etc motivate a per-channel spec relaxation. The
"right" distance may be 100m, 220m, or something else; it will be
determined later. Implementing 100G with SFP+ isn't attractive, but
SFP+ could well be appropriate for 40G, especially if cost is the main
concern. The SFP is the most cost-effective OE transceiver vehicle on
the planet (in cost/Gb/s), and that is likely to be the case for quite
some time. While not as high-density as parallel optical MSA'd modules
such as SNAP12 and QSFP, the SFP (including SFP+) has advantages besides
cost, e.g. straightforward implementation of SMF products for 10km reach
and more. At 100G, the need for density is extreme, hence the need for
a parallel-optical module. At 40G, the need for bandwidth density is
not as high, the density advantage of parallel optics is reduced, and
4x10G implementations use only 8 of the 12 channels available. At 40G,
the viability of an (4x)SFP+ PMD implementation is real, and its
advantages may be compelling. Moreover, the SFP+ can cost-effectively
utilize the -SR and -LR specs defined in 802.3ae.
From: Scott Kipp [mailto:skipp@BROCADE.COM]
Sent: Monday, May 14, 2007 4:04 PM
Subject: Re: [HSSG] 10 x 4 = 40
I have reviewed your proposal regarding 40G = 4 X 10G and think there
may be a disconnect between 40GBase-SR and 4 X 10GBase-SR. The HSSG is
considering defining 100GBase-SR (and thus 40GBase-SR) to span only 100
meters instead of 300 meters defined in 10GBase-SR. Each lane of 100G
and 40G does not need to be defined with the difficult 300 meter
requirements of the 10GBase-SR standard. If each 10G lane of the 100G
or 40G PMDs would only be required to span 100 meters, the cost of the
HSSG solution would be lower cost per channel than 10GBase-SR.
The supported distance of each 10G lane is important because it has
large cost implications. I would like to quote a Finisar proposal
regarding the manufacturability of 10GBase-SR transceivers that can
found here: http://www.t11.org/ftp/t11/pub/fc/pi-4/06-036v0.pdf
On slide 5, the Finisar presentation states:
Practical 10G VCSELs to date have been small aperture MM devices.
- Yield VERY poorly even to largest allowed spectral width - This is
largest single cost driver for 10GBASE-SR
Then on slide, 6, Finisar and Advanced Optical Components - the largest
VCSEL manufacturer in the world states:
Practical TX design almost impossible. Requires high ER and expensive
yielding and testing
Finisar showed the difficulties of manufacturing 10GBase-SR transmitters
(5 years after standardization) because of the 300 meter requirement
over OM3 fiber. This presentation was pivotal in defining 8 Gigabit
Fibre Channel (8GFC) in a low cost manner that only spans 150 meters at
8.5 Gbps. If the 300 meter requirement is placed on 100G Ethernet and
thus on 40G Ethernet, then the cost of 40G and 100G will be tremendous
and will see low adoption.
Therefore, the 4 X 10GBase-SR = 40G argument is not necessarily true and
will depend on how the HSSG defines each 10G lane.
If the HSSG defines 10G lanes to only 100 meters, then the PMDs may not
require clock and data recovery (CDR) chips in the transceiver like
those used in the XFP transceiver. The QSFP transceiver that supports
four lanes of 10G does not use a CDR and is expected to be significantly
lower cost than 4 XFPs. In other words, 4 XFPs do not equate to 1 QSFP.
The cost of a QSFP may equate to 4 SFP+s. Likewise, a low cost QSFP may
be made that is compliant to 40GBase-SR, but not compliant to 4 X
One of the goals of 40G is not to have a 'perception of being "low-end"'
but to actually be low end in cost. If history repeats itself, cost
will be a determining factor in adoption of 100G and 40G.
An interesting example of high speed links, can be seen in
telecommunications. OC-768 systems that run at 40G serial are state of
the art right now and should be for the foreseeable future. OC-192 is
seeing very low volumes and this could be a problem with 100GE if there
is a "early adopter premium". OC-768 is not economical now at 6x or 7x
the costs of 10G according to an article titled "What's holding up
80%99s-holding-up-40G.) An interesting aspect of this article states:
"What's attractive about 10-GigE isn't necessarily the technology. It's
that once a chip is manufactured, it gets shipped in volumes of
millions, not in volumes of a few thousand."
With less than a million ports of 10GE ever shipped worldwide, this
statement is false and 10GBase-SR's lofty distance requirements is one
of the reasons why. The HSSG should look into examples of high data
rate connections (especially 10G) to get 100GE and 40GE right.
QSFP Chair and Editor
Office of the CTO, Brocade
From: Hugh Barrass [mailto:hbarrass@CISCO.COM]
Sent: Friday, April 13, 2007 3:53 PM
Subject: [HSSG] 10 x 4 = 40
There's been some discussion (!) around the existence of an MSA for a
40G module format. The module is actually based on 4 x 10G channels,
this leaves system implementors 2 choices:
1. Simply define the MSA to use LAG . The MAC & PCS are already defined
for 10GBASE-R, the PMD definitions are already available for SR, LR &
LRM. This could be incorporated into systems being developed
immediately, exploiting existing MAC and fabric silicon. From a
standards perspective, I would classify this as another 10G format (no
fundamental difference to X2, XFP or SFP+).
Additionally, a breakout device could allow compatibility with discrete
10G systems (using SFP+, XFP, X2 etc.) and also would allow the use of a
40G socket to connect to multiple 10G destinations (redundant
connections, multipath routing etc.).
2. Try to push through a new definition in 802.3 for 40G MAC and PCS.
This would almost certainly be tied to the same schedule as the 100G MAC
& PCS definition, it might be available to start development in 3-4
years. It would require new MAC/fabric silicon, that would have to start
development after the standard is in its last stages of development.
A socket using the single 40G approach could not be connected to a
breakout for legacy compatibility.
If #1 happens (almost impossible to "prevent" it) then confusion will
ensue as option #1 & option #2 products mix in the market. It will be
very difficult to distinguish or differentiate between the two. I don't
know how those who commit to the "proper" approach of #2 will be able to
recoup their extra development costs compared to those who get a 3-4
year headstart by implementing #1. Additionally, option #2 based
products will hit the market at the same time as 100G products become
available. They will start with the perception of being "low-end" and
will not be able to command the "early adopter premium" that is often
relied on to recover leading edge development costs.
Frankly, looking at this, I would not recommend to my employer that we
should spend time (and money) to develop the silicon to support option
#2 vs option #1. Of course, others may feel free to spend their
development differently. Additionally, if I was a component vendor, I
know which option I would pursue.