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Karen, While I have heard discussion of breakout to 16 lanes of 25GbE from a module like CDFP, I propose that it would be a very small niche. Breakout is not an objective
in 802.3bs. The CDFP was designed to support 13 CDFP in a 19” switch to enable 5.2Tb/s of throughput (13 X 400G) while a QSFP28 can support 1.8Tb/s in one row (18 X 100G),
so CDFP can provide about three times the bandwidth density in a single row. The high density of the electrical channels of the CDFP makes belly-to-belly or stacked configuration very challenging, so it is difficult to scale CDFP to more than one row of modules
to deliver 10.4 Tbps (2 X 13 X 400G) in 1U. The QSFP28 on the other hand is commonly used in a belly-to-belly or stacked configuration to yield 3.6Tb/s (2 X 18 X 100G). Kind regards, Scott From: Karen Liu [mailto:karen@xxxxxxxxxxxxx]
There’s an assumption below that optics dominates the module size. It’s unclear to me that’s going to remain true. I think this comes from additional implicit
assumptions from the way things have been done to date, maybe about linear arrays. This seems akin to assuming optics will always be NRZ. As we go forward, the optics just have to get a little bit cleverer. Electronics isn’t built all in linear layout. With some clever layout, we think should be possible to get dense 16-lane modules even for single-mode. A key metric from an application standpoint is face-plate
density. CDFP isn’t allowing the 2x, 4x, etc desired growth in power density per 19” rack. Is there a need for a narrower (physically) electrical interface that would support SR16 breakout to 25G?
Best, Karen From: Ali Ghiasi [mailto:aghiasi@xxxxxxxxx]
Scott On a separate email to John/Joel/Vasu I raised the concern defining 50G signaling to address CDAUI-8 applications could potentially tie our hand when defining the high volume cost sensitive 50 GbE based on 1x50G (LAUI). It will be more
constructive to define 50G signaling in the project that also defines 50 GbE, a clear set of application requirements potentially could drive the consensus something we lack now. As far as the real 400GbE application 2km/10 km
the optics will dominate the module size, a narrower interface will not immediately help. On the other hand the only PMD the group had consensus to date to adopt has been 400Gbase-SR16 based on CADUI-16, a CADUI-8 interface will force 400Gbase-SR16
to use an inverse mux/gearbox of some sort. Considering break out applications, with 25 GbE standardization under way the right interface will be CDFP with CDAUI-16 and not a CDAUI-8 interface. Based on the current dynamic of the group, I am not sure we will reach consensus in the bs project on the 50G signaling with both NRZ and PAM4 looking viable to address CADUI-8 applications. During Q3-14 OIF probably took the right approach
by accepting both NRZ and PAM4 as bases for the 50G XSR/VSR/MR interfaces. Thanks, Ali Ghiasi Ghiasi Quantum LLC
On Dec 19, 2014, at 8:04 AM, Scott Kipp <skipp@xxxxxxxxxxx> wrote:
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