Re: [802.3_50G] CAUI-4 operating modes

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Chris and others,

I am a bit confused. Strictly speaking, no host has 50G Ethernet today so when one is built to have 50G Ethernet it can also be built to have any required FEC.

Are you mentioning KR4 and KP4 just to give a flavor of the difference in these two potential codes to be adopted? In this way, when mentioning KR4, you mean LAUI-2 could be devised to need to coding gain itself just as CAUI-4 does not need any coding gain to operate.

Jeff

From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Wednesday, February 24, 2016 1:47 PM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_50G] CAUI-4 operating modes

Mike,

The optics we would use with LAUI-2 with KR4 RS-528 FEC would be the same optics as those we would use with LAUI-2 with KP4 RS-544 FEC, except running at 3% lower rate. The SG will have to decide which we define in the project, and which outside of the project, if any.

Chris

From: Mike Dudek [mailto:mike.dudek@xxxxxxxxxx]
Sent: Wednesday, February 24, 2016 12:05 PM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_50G] CAUI-4 operating modes

But what PMD is LAUI-2 going to support. If we don’t have an objective for a PMD that requires it then in my opinion it would be out of scope to develop it without an explicit objective.

Mike Dudek

QLogic Corporation

Director Signal Integrity

26650 Aliso Viejo Parkway

Aliso Viejo CA 92656

949 389 6269 - office.

Mike.Dudek@xxxxxxxxxx

From: Kapil Shrikhande [mailto:kapils@xxxxxxxx]
Sent: Wednesday, February 24, 2016 11:32 AM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_50G] CAUI-4 operating modes

To match the capabilities of CAUI-4 (4x25G), the LAUI-2 (2x25G) C2M interface should operate without FEC at a BER of 1e-15 or better (Gary also points to the BER requirement for CAUI-4), so that a no-FEC PHY using LAUI-2 could operate at 1e-12. And as stated by Chris, LAUI-2 will also support RS-FEC encoded signal (KR4 and KP4 FEC) for those PMDs that require FEC.

Kapil.

On Wed, Feb 24, 2016 at 10:53 AM, Brad Booth <bbooth@xxxxxxxx> wrote:

I like this topic as it does highlight one of the aspects previously mentioned in January about the need to have a low or zero FEC latency AUI.

For the 25G-based interface (CAUI-4), the task force(s) wisely provided the ability for the interface to operate with and without FEC. This has permitted flexibility in implementations. For example, the ability to use a CAUI-4 without FEC between an Ethernet adapter's ASIC and FPGA will permit a low latency interface; whereas, between the adapter's FPGA and the switch's ASIC, FEC can be used to provide end-to-end error correction.

It would be great if we continue to provide interfaces like CAUI-4 that can transport either FEC or non-FEC data. This would provide the greatest level of flexibility for various implementations that could occur.

I've requested time to make a presentation in Macau to discuss these use cases in both the 50G and 100G market.

Thanks,
Brad

On Wed, Feb 24, 2016 at 10:31 AM, John D'Ambrosia <jdambrosia@xxxxxxxxx> wrote:

Chris,

You are mistaken.

The FS FEC was developed and a 4 lane solution was developed but it was not CAUI-4. That was done in 802.3bm. There is no way I would ever try to steal that credit away from Dan Dove who had the fortitude of a saint with that effort.

I think the confusion is coming from FEC and non-FEC protected interfaces.

From what I see

802.3bj RS-FEC clause developed to support the cr4, -kr4, -kp4

802.3bm developed CAUI-4 and specified its operation to 10^-15 without FEC. However the architecture itself can be done in such a way that the CAUI-4 is carrying either non-FEC or FEC protected data. 802.3bm also developed -sr4 where FEC is mandatory.

So the AUI based on 25Gb/s signaling can be independent of whether there is FEC or not.

I think everyone is right, but it clearly points out we have to be very specific with language.

John

From: Chris Cole [mailto:chris.cole@xxxxxxxxxxx]
Sent: Wednesday, February 24, 2016 1:24 PM
To: John D'Ambrosia <jdambrosia@xxxxxxxxx>; STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_50G] CAUI-4 operating modes

CAUI-4 with KR4 RS-528 FEC was developed in the P802.3bj project you led to first support CR4. P802.3bm then defined SR4 with CAUI-4 with KR4 FEC. This enable subsequent efforts to quickly define optical PMDs that use KR4 FEC. P802.3bm also defined CAUI-4 with no FEC to support existing PMDs; LR4 and ER4.

So coming out of 802.3bm we had two CAUI-4 operating modes, one without FEC for backwards compatibility, and one with FEC for new PMDs.

Chris

From: John D'Ambrosia [mailto:jdambrosia@xxxxxxxxx]
Sent: Wednesday, February 24, 2016 10:04 AM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_50G] CAUI-4 operating modes

Reading the spec – it looks more like the specification of CAUI-4 is done not assuming FEC, but a port type may include FEC that could go over the CAUI-4.

From: Rick Rabinovich [mailto:rrabinovich@xxxxxxxxxxx]
Sent: Wednesday, February 24, 2016 12:20 PM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_50G] CAUI-4 operating modes

Correct, CAUI-4 does not include FEC.

Rick Rabinovich

Hardware Architect – Signal Integrity

rrabinovich@xxxxxxxxxxx

Phone: +1 (818) 208-7328

26601 W. Agoura Rd.

Calabasas, CA 91302 US

visit: www.ixiacom.com

From: Gary Nicholl (gnicholl) [mailto:gnicholl@xxxxxxxxx]
Sent: Wednesday, February 24, 2016 9:18 AM
To: Rick Rabinovich <rrabinovich@xxxxxxxxxxx>
Cc: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: Re: CAUI-4 operating modes

Perhaps, but 802.3bj did not define CAUI-4 and Chris’s comment was specifically on CAUI-4.

Gary

From: Rick Rabinovich <rrabinovich@xxxxxxxxxxx>
Date: Wednesday, February 24, 2016 at 12:15 PM
To: Gary Nicholl <gnicholl@xxxxxxxxx>
Cc: "STDS-802-3-50G@xxxxxxxxxxxxxxxxx" <STDS-802-3-50G@xxxxxxxxxxxxxxxxx>
Subject: RE: CAUI-4 operating modes

Hi Gary,

Thank you for bringing this up . CAUI-4 defined in IEEE802.3bm was specified without FEC to eliminate the latency incurred.

Perhaps Chris was also referring to 4x25G as defined in IEEE802.3bj which includes RS-FEC for 100GBASE-CR4.

Cordially,

Rick Rabinovich

Hardware Architect – Signal Integrity

rrabinovich@xxxxxxxxxxx

Phone: +1 (818) 208-7328

26601 W. Agoura Rd.

Calabasas, CA 91302 US

visit: www.ixiacom.com

From: Gary Nicholl (gnicholl) [mailto:gnicholl@xxxxxxxxx]
Sent: Wednesday, February 24, 2016 9:08 AM
To: STDS-802-3-50G@xxxxxxxxxxxxxxxxx
Subject: [802.3_50G] CAUI-4 operating modes

Following on from the discussion this morning I checked 802.3bm and there is only a single operating mode for CAUI-4.

CAUI-4 C2M is defined in Annex 83E. There is only one operating mode and that assumes no FEC.

There is no separate FEC operating mode, where some of the FEC gain is used to relax the CAUI-4 electrical specifications.

In 802.3bm if RS-FEC is being used, it is carried completely transparently over the CAUI-4 interface, and all of the FEC gain is used for the PMD (i.e. 100GBASE-SR4). The CAUI-4 specification is completely independent of whether FEC is being used on the link or not. Perhaps this is what Chris meant by “two CAUI-4 operating modes” on the call this morning, even though from a CAUI-4 perspective there is only a single operating mode?

Another way to state this is that the FEC requirements for the host are defined by the PMDs to be supported and not the CAUI.

Gary