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From: Grow, Bob [mailto:firstname.lastname@example.org]
Sent: Monday, February 18, 2008 9:20 AM
Subject: Re: [802.3BA] Why 40GE and not 50GE?Michael:I believe the original 40 Gb/s rate was primarily based on the anticipated lower cost of using 4 X existing 10 GbE PHY technology. Four lanes has significant history in our data paths (e.g., 1000BASE-T, 10GBASE-X4 PMDs, XAUI, etc.) When P802.3ap was in development, it was generally expected that backplanes could and would be built with 4 10GBASE-KR channels going to a slot, allowing a future upgrade to 40 Gb/s through a single MAC. Similarly, in the HSSG many advocates used assumed that other 10GBASE-R technologies could be used in a four lane configuration to provide a higher speed connection for servers at lower cost than 100 Gb/s. OTN compatibility at 40 Gb/s was not an original driving force in the choice of speeds for most advocates. Just as 10 GbE is 10.0000 Gb/s, so also did the original advocates for 40 Gb/s mean 40.0000 Gb/s.--Bob
From: Frankel, Michael [mailto:MFrankel@CIENA.COM]
Sent: Monday, February 18, 2008 7:11 AM
Subject: [802.3BA] Why 40GE and not 50GE?
I appologize ahead of time if this question has been addressed. I looked over past HSSG material, and cannot find any info on how specific 40GE rate came about (as opposed to 50 GE). 40G simply appears as a "fact" in all the presentations.
Is 40G a default selection because of its ties to OC768 and OTU3?
The only item I found is Slide 5 of following presentation mentions PCIe x16 Gen2 as 50 Gbps of bandwidth.