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
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