Re: [802.3_100GNGOPTX] Reach on MMF
All,
I am thrilled to see the discussion, and hope it stimulates some
detailed proposals for objectives that include justifications and data.
For MMF, I would really like to see some data that shows how far you
can run on OM3/OM4 using feasible VCSELs, a reasonably practical
receiver, perhaps some channel compensation and/or FEC, and maybe even
broken down into a couple of different reach values based on
with/without EQZ/FEC.
Then, lay that against a histogram of reach requirements in the data
center, and a proposal to set the reach based on the balance point
between cost/feasibility and market potential.
Anyone working on this?
Dan
On Mon, 10 Oct 2011 16:56:58 -0500, Brad Booth <Brad_Booth@xxxxxxxx>
wrote:
> Matt,
>
> Clarification:
> Paul's data didn't include SFP+ DAC. My point was only that I've seen
> data showing a strong trend for DAC for the access channel.
> Personally, I assumed that some of the short links in Paul's data
> would also be used for the access channel; however, Paul believes that
> assumption should not be made.
>
> Maybe this would be a good area to provide some clarification at the
> next meeting on architecture and reaches, so that everyone is using
> the same terms and assigning the data to the correct buckets.
>
> Thanks,
> Brad
>
>
> -----Original Message-----
> From: Matt Traverso (mattrave) [mailto:mattrave@xxxxxxxxx]
> Sent: Monday, October 10, 2011 4:48 PM
> To: Booth, Brad; STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: RE: [802.3_100GNGOPTX] Reach on MMF
>
> Paul,
>
> I thought I understood the thread until Brad stated, "That would
> track accordingly with the numbers I've been seeing for SFP+ DAC in
> ToR and EoR configurations." This seems to imply that SFP+ direct
> attach cables are included in your data - is that right?
>
> Also, I would like to understand if you have looked at the ratio of
> equipment cord to link cabling. Without understanding more than your
> explanation I would assume that some excess could be attributed to
> server to ToR applications? Is that a fair assumption?
>
> thanks
> --matt
>
> -----Original Message-----
> From: Brad Booth [mailto:Brad_Booth@xxxxxxxx]
> Sent: Monday, October 10, 2011 2:29 PM
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: Re: [802.3_100GNGOPTX] Reach on MMF
>
> Paul,
>
> I understand. It is a different point of view on how the data may be
> interpreted. For example, how many of the < 10 m links terminated vs
> were part of a longer connection? If I remember correctly, you
> presented the data based upon a multiple-link topology.
>
> I interpreted the data as indicating both multiple-link and
> single-link (for ToR and EoR). Given the trends in ToR and EoR, my
> assumption was a growing percentage of those short links are used in
> those topologies. That would track accordingly with the numbers I've
> been seeing for SFP+ DAC in ToR and EoR configurations.
>
> Cheers,
> Brad
>
>
>
> -----Original Message-----
> From: Kolesar, Paul [PKOLESAR@xxxxxxxxxxxxx<mailto:PKOLESAR@xxxxxxxxxxxxx>]
> Sent: Monday, October 10, 2011 04:13 PM Central Standard Time
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: Re: [802.3_100GNGOPTX] Reach on MMF
>
>
> Brad,
> While I'm sure it is no surprise to you that I also strongly advocate
> MMF reach objectives that allow seamless upgrade from 40G to 100G, I
> would like to understand your assertion that my data "indicated that
> there was a large number of single reach hops that were under 10 m."
> While my cord data shows about 85% under 10m, my single channel
> topology (equip. cord + link + equip. cord) data showed 0% coverage at
> 10m (~30ft). Perhaps this is a terminology issue with single cords
> being treated as single reach hops. While I do not deny that cords
> are sometimes used that way, I would be very hesitant to try to infer
> single-cord channels from the general population of cords.
> Unfortunately I know of no means to isolate the two populations within
> the data.
>
> Paul
>
> -----Original Message-----
> From: Brad Booth [mailto:Brad_Booth@xxxxxxxx]
> Sent: Monday, October 10, 2011 3:48 PM
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: Re: [802.3_100GNGOPTX] Reach on MMF
>
> Paul,
>
> Thanks for the clarification. My intention was not to imply that you
> were espousing the use of copper cabling for all access switch to
> server connections, only to highlight that trends are changing to what
> was considered a "typical" topology.
>
> I do agree with you on understanding the different mixtures of
> infrastructure with the caution to be every diligent with respect to
> power, cost and market size. It's that infamous 80-20 rule. There is
> no point in having 80% of the market have to absorb a disproportionate
> burden to satisfy the other 20% of the market. Hopefully with some
> hindsight on previous decisions plus some general understanding of the
> market trends, the study group can make some better predictions of
> future requirements. Although, crystal balls have not been known to be
> reliable. ;-)
>
> Cheers,
> Brad
>
>
> -----Original Message-----
> From: Kolesar, Paul [mailto:PKOLESAR@xxxxxxxxxxxxx]
> Sent: Monday, October 10, 2011 3:19 PM
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: Re: [802.3_100GNGOPTX] Reach on MMF
>
> Brad,
> In my September contribution that you referenced below, my diagram
> labeling was indicative of present practice. I was not trying to
> imply that going forward the 100G access channels should remain
> copper, so thank you for allowing me the opportunity to clarify.
>
> On the 802.3 subcommittee's present course P802.3bj will define a
> copper solution that reaches at least 5m. While 5m is sufficient for
> Top-of-Rack and adjacent rack connections, it cannot well address
> Centralized, End-of-Row or most Middle-of-Row switch placements.
>
> Given that access channels greatly outnumber aggregation channels, I
> would have to agree that the access part of the data center network
> deserves due consideration. To that end, the migration of access
> channels to different mixtures of Centralized, ToR, EoR and MoR should
> be a key focus of our studies. Here we should attempt to predict the
> mixture that will be deployed in the coming years as 100G becomes the
> norm. The contribution flatman_01_0311.pfd (presented to the study
> group that became the P802.3bj task force) has some material on this
> topic. While good predictions on 10G trends extracted from Dell'Oro
> data run beyond their headlights after 2012, it shows a strong
> tendency towards ToR which likely applies to 40G and 100G as well.
> I'm hoping for more clarity for the years after that, because as shown
> later in Alan Flatman's contribution, 100G server volumes don't pick
> up until 2018. For comparison, 100G aggregation channels start at
> least three years earlier.
>
> Some may lament that our ability to predict the needs of the market
> seven years out is spotty. It remains to be seen if the group has the
> appetite to repeat such endeavors, or will instead choose to focus on
> the best solutions for the nearer-term aggregation channels...
>
> Regards,
> Paul Kolesar
>
> -----Original Message-----
> From: Brad Booth [mailto:Brad_Booth@xxxxxxxx]
> Sent: Monday, October 10, 2011 1:42 PM
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: Re: [802.3_100GNGOPTX] Reach on MMF
>
> I believe that if the study group is going to set a reach objective
> for a 100GBASE-SR4 port type, that it would be highly recommended that
> we support the same reach as the 40GBASE-SR4. End users that have gone
> through the effort to install ribbon fiber OM3 or OM4 fiber to support
> 40G will be much happier with us if we permit them to re-use the same
> fiber for 100G. Forklift upgrades of equipment and cabling also slows
> deployment of the technology, so from a broad market potential and
> economic feasibility standpoint, supporting the same reach as 40G just
> makes good sense.
>
> As for SMF solutions, it would be good to understand the relative
> cost difference between a 100G LR4 module that is required to meet the
> 10 km reach vs one that is shorter. For those that may remember
> 802.3ae, there was a 2 km SMF reach objective. That was the target
> reach for campus networks with 10 km and 40 km targeting the MAN. It
> was discovered that the relative cost difference between 2 km and 10
> km was insignificant and that by bundling them into one port type
> 10GBASE-LR, the task force could increase the market potential for
> that device.
>
> As we stand today, 802.3ba has a huge reach and cost discrepancy
> between the 100/150 m MMF solution and the 10 km SMF solution. In my
> humble opinion, we need to understand the potential impact to the cost
> (in relative terms) between a solution that can satisfy the campus
> market vs. the one specified for the MAN. There are some that would
> also like to use SMF within the data center without the cost burden
> associated with 100GBASE-LR4. The key will be to understand if there
> is a breakpoint of reach vs. cost that makes the solution economically
> viable and has good market potential.
>
> The one other aspect that concerned me during the study group meeting
> was that in Paul Kolesar's slides there was a diagram of the network
> architecture. I think that diagram is a bit outdated, but that wasn't
> the main reason I was concerned. What I noticed was that the
> connection from the access switches to the servers was labeled "Copper
> horizontal cabling". Why was that connection being assumed to be
> copper? The data Paul showed indicated that there was a large number
> of single reach hops that were under 10 m. Paul also highlighted that
> there was a trend to longer MMF reach. This makes complete sense if
> one assumes that data centers are transitioning from centralized
> switches to end-of-row or top-of-rack switches. Paul's data correlates
> very well with information that I've received about the movement from
> centralized to end-of-row (or center-of-row). That being said, maybe
> there is another cost breakpoint for shorter MMF links, say 15-20 m.
> That to me would be interesting !
> data to have for comparison and objective setting.
>
> Thanks,
> Brad
>
>
> -----Original Message-----
> From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxxxxx]
> Sent: Monday, October 10, 2011 12:32 PM
> To: STDS-802-3-100GNGOPTX@xxxxxxxxxxxxxxxxx
> Subject: [802.3_100GNGOPTX] Reach on MMF
>
> Hi
>
> It great to get some end users feedback on MMF reach, as you know
> 40Gbase-SR4 has reach of
> -100 m on OM3
> - 150 m on OM4
>
> Single mode PMD is also with in the scope of 100GNGOPTX study group,
> when the days come that single mode PMDs are low cost, power, and size
> then I expect MMF ribbon reach could get limited to 10's meters. I
> have my finger crossed for that day!
>
> Now with reality and unknown in front of us if the ultimate PMD could
> be developed, what should the reach of
> 100Gbase-SR4 be?
>
> Historically single mode PMDs have been larger, higher power, and
> higher cost. For example 100GBase-SR10
> is supported in the CXP form factor and 100Gbase-LR4 is supported in
> the CFP form factor, the CFI presentation slide 11
> http://www.ieee802.org/3/100GNGOPTX/public/jul11/CFI_01_0711.pdf
> shows 32 ports of CXP and only 4 ports of CFP! So for some period of
> time we could find ourself that the MMF PMD is the only option on the
> highest density platform. This is why we need to carefully study this
> subject specially with in the context of larger data centers see slide
> 7
> http://www.ieee802.org/3/100GNGOPTX/public/sept11/ghiasi_01_a_0911_NG100GOPTX.pdf
>
> Thanks,
> Ali