Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs

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Thanks,

Ali Ghiasi

Ghiasi Quantum LLC

Office (408)352-5346

On Dec 4, 2015, at 10:30 AM, Trowbridge, Stephen J (Steve) <steve.trowbridge@xxxxxxxxxxxxxxxxxx> wrote:

Hi Mike,
I also disagree with Ali’s comment.
All of the interfaces we have specified for which KR4 FEC was “good enough” were based on 25G NRZ lane technologies. Even for 12.5Gbaud PAM4 over a 1m channel, we used the KP4 FEC. It hardly seems credible that you could do 50GBaud PAM4 to 500m or 25GBaud PAM4 to 2km or 10km with less of a FEC than you need for 12.5Gaud PAM4 over a 1m backplane. Furthermore, it doesn’t seem the right tradeoff to skimp on the FEC, which more and more disappears into the silicon, at the expense of having much more stringent requirements on the components which lead to higher cost.
Regards,
Steve

From: Mike Dudek [mailto:mike.dudek@xxxxxxxxxx]
Sent: Friday, December 04, 2015 11:07 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

I agree that this is a big issue and one that definitely needs to be addressed.

I disagree with Ali’s comment on a different sub-thread that “100 GbE should be using KR4 FEC”. I think we need to look at the problem as a whole and determine what is the best solution.

We have existing 100G optical PMD’s that use “no FEC” and “KR4 FEC”.    We are considering future 100G PMD’s (based on 802.3bs) that are defined with KP4 FEC.   (To reduce the cost of 100G.   If not why would we be considering them!!!)

The C2C and C2M specifications in 802.3bs use the KP4 FEC and making them work for KR4 FEC would require significant additional work and probably a relaxation in reach requirements.

So what is going to be the optimum solution?
1.      A forward looking new 100G solution that uses KP4 FEC and leverages the 802.3bs work that would provide the lowest cost solution with the new optical PMD’s but requires modules that have CAUI2 inputs and use “legacy” optical interfaces to incorporate KP4 FEC encode/decode in the module.
2.      A solution based on KR4 FEC that would probably require relaxed reach requirements for C2C and C2M CAUI-2 (compared with the use of KP4 FEC) but would not require FEC decoder/encoder for 100GBASE-SR4 and the non-IEEE standards of CWDM4 and 100G PSM4. It would require KR4 FEC encoder/decoder in a CAUI-2 module for LR4 and a KR4/KP4 transcoder in the module for new optical PMD’s that need KP4.

Note that I suspect if 100G uses KR4 FEC and this work is within 802.3bs then it will delay 802.3bs.    If however the KP4 FEC is used then I don’t see a delay for 802.3bs.

Mike Dudek
QLogic Corporation
Director Signal Integrity
26650 Aliso Viejo Parkway
Aliso Viejo CA 92656
949 389 6269 - office.
Mike.Dudek@xxxxxxxxxx

From: Jeffery Maki [mailto:jmaki@xxxxxxxxxxx]
Sent: Thursday, December 03, 2015 5:45 PM
To: Mike Dudek <mike.dudek@xxxxxxxxxx>; STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: RE: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

Mike,

If we can decide that KR4 FEC will not have sufficient performance for CAUI-2 C2C and/or C2M, it shall have big impact on how other things proceed or not. Without the use of an extender sublayer, one will have no means of interoperation other to run the new 50G lanes at 25G.

Jeff

From: Mike Dudek [mailto:mike.dudek@xxxxxxxxxx]
Sent: Thursday, December 03, 2015 12:15 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

It won’t be a slam-dunk to create a CAUI-2 using KR-FEC when the CDAUI-8 is using KP-FEC. Also if we are considering 100GBASE-DR or 100GBASE-LR2 those are likely to want the KP-FEC.     I expect also that the 50G serial backplane and copper links are going to want the KP4 FEC.   Ie the KP-FEC will be in any chips designed for 50G PAM4.

Mike Dudek
QLogic Corporation
Director Signal Integrity
26650 Aliso Viejo Parkway
Aliso Viejo CA 92656
949 389 6269 - office.
Mike.Dudek@xxxxxxxxxx

From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxx]
Sent: Thursday, December 03, 2015 12:00 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

Jeff,
If I get your point here – the only thing you are adding to what I already pointed out was the interaction between a x2 C2C with a x4 C2M.

Right?

John

From: Jeffery Maki [mailto:jmaki@xxxxxxxxxxx]
Sent: Thursday, December 3, 2015 2:37 PM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

I support what Chris is saying. In addition, I think we will need to examine support of existing 100G PMDs with a new optional electrical interface, the CAUI-2 (2x50G) C2M. Further, we should examine CAUI-2 C2C, where the C2M interface is CAUI-4. The desire for things to persist to work with KR4 FEC rather than requiring a new FEC code shall be high.

Jeff

From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Thursday, December 03, 2015 8:53 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: Re: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

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.

However, the inclusion of 100G in the 400G project is much less clear. Several arguments can be made that it more naturally belongs in the 50G project. An important consideration is that for both 50G and 100G, backwards compatibility with existing 25G I/O interfaces is important. Specifically we will want 50G supported with 2x25G electrical I/O and 100G to be supported with 4x25G I/O (CAUI-4). This suggests that for 50G single wavelength and 100G WDM2 solutions, KR4 is the appropriate FEC. For both, this gives reasonable optical margin with PAM4 modulation. On the other hand, for 200G WDM4 KP4 is a better choice, same as for 400G WDM8.

Adding only 200G to the 400G project makes for much cleaner documentation modification. Broad market potential for 200G is the same as for 400G. We don’t need to introduce new justification which is required for 100G. Not having 100G, removes any dependence on any other project, so there is no need to discuss this.

Chris

From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxx]
Sent: Thursday, December 03, 2015 6:00 AM
To: STDS-802-3-400G@xxxxxxxxxxxxxxxxx
Subject: [STDS-802-3-400G] New 50G/100G/200G SG - Potential Impact on 802.3bs?

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. Seehttp://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 seehttp://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