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Hi Steve, We selected 400GBASE-DR4 based on measurements using lab grade equipment. Before we start proliferating the to be agreed 400GBASE-DR4 spec, it might be prudent to see measurements of an actual implementation
in a promised technology, for example SiPIC. Chris From: Trowbridge, Stephen J (Steve) [mailto:steve.trowbridge@xxxxxxxxxxxxxxxxxx]
Hi Chris, I have some sympathy for the idea that in the near term (say the next 5 years), you can probably build a simpler, cheaper, lower power 100GBASE-FR2 than 100GBASE-DR, just as you can probably build a simpler,
cheaper, lower power 400GBASE-FR8 than a 400GBASE-DR4. But given that we have a 400GBASE-DR4 over parallel fiber in the P802.3bs project, why would 50Gbaud PAM4 be the right modulation for that interface and not for a single-lane 100GBASE-DR done in the same timeframe?
I would think the PMD specs would be exactly the same. The only difference might be the FEC architecture if you couldn’t stomach a 4x increase in latency to use the same interleaving as P802.3bs. Regards, Steve From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
John,
We are once again reminded that trying to predict the future by more than one technology generation ahead is a low probability of success activity and therefore should not be done in standards bodies.
From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxx]
Chris, I am not getting your point here – how are we introducing further delay? We already have DR4 in the 400G standard. What additional delay will there be to just have a single lane implementation? John From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Hi Steve One reason we may not want to do 100GBASE-DR in 802.3bs is to not add considerably delay to the 802.3b schedule while we debate the merit of supporting measurements. And given the research results we are seeing
presented in recent technical publications and conferences, we are sure to see the modulation debate re-opened, which is an even better prescription to delay 802.3bs schedule. Chris From: Trowbridge, Stephen J (Steve) [mailto:steve.trowbridge@xxxxxxxxxxxxxxxxxx]
Hi Chris and Rob, Just to play devil’s advocate here, I think it depends on the objectives agreed in the study group. If the only stuff we have objectives to do for 200G are the same things we are doing at 400G with fewer lanes, sure, it all folds right in to P802.3bs. Specifically: We would specify 8-lane CCAUI-8 and 4-lane CCAUI-4 C2C and C2M interfaces. We would specify 200GBASE-SR8, 200GBASE-DR2, 200GBASE-FR4, and 200GBASE-LR4 PMDs. But the flies in the ointment would be if we have objectives to build a 200GBASE-SR4, 200GBASE-CR4, or 200GBASE-KR4 PMD, which I think would be quite challenging on the current P802.3bs schedule. Presumably the reason you think 100G belongs with 50G is that you assume this project needs to do interfaces like 100GBASE-SR2, 100GBASE-CR2, 100GBASE-KR2. But why wouldn’t you do, for example, a 100GBASE-DR
interface in the P802.3bs project? Regards, Steve From: Rob (Robert) Stone [mailto:rob.stone@xxxxxxxxxxxx]
Chris I agree with your observation, and I have been thinking the same thing with respect to the partitioning of the work. It would seem that if possible, using the KR4 FEC for 50 and 100G would have a lot of benefits with respect to compatibility with existing MAC rates and 25G based technologies. I would expect that it is likely
we will see co-existence of 25 and 50G / lane technologies within the same environment, and if so we should make an effort when defining the logic to enable straightforward low power connections between the different generations. Using end – end KP4 FEC would
help facilitate that. Thanks Rob From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
The idea of rolling 200G into the 400G project is compelling. In prior discussions, we had rejected this as too late for 802.3bs TF, so it’s encouraging to see we are willing to revisit. One mental test of why
this makes sense is to consider what we would have done in 400G Study Group if we knew what we know now. Given the CFI support, it could be argued that most people would have supported both 200G and 400G. If anything, 200G is more compelling.
Chris From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxx]
Dear Task Force Participants, This email is to make sure that everyone is aware of conversations happening in the 50/100/200G Study Group Phone Conference that happened yesterday – Dec 2. There has been discussion at how the multi-lane 100G/200G solutions might be
rolled into the 802.3bs project. To that end – I gave a presentation at the conference call that looked at potential modifications / additions to our PAR / CSD. See
http://www.ieee802.org/3/50G/public/adhoc/archive/dambrosia_120215_50GE_NGOATH_adhoc_v2.pdf I encourage everyone to review this presentation and consider the findings on the last few pages. Individuals may wish to participate in the upcoming 50/100/200G ad hoc calls that Mr. Nowell has planned. For more information see
http://www.ieee802.org/3/50G/public/adhoc/index.html. I will be working on the meeting announcement for the January interim, and anticipate that there will be a joint session of our Task Force with the Study Groups to further consider these implications. Regards, John D’Ambrosia Chair, IEEE P802.3bs 400GbE Task Force |