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Re: [802.3BA] 802.3ba XR ad hoc next step concern

Message text written by "PETRILLA,JOHN"
>In flatman_01_0108, page 11, there's a projection for 2012.  There for
40G, the expected adoption percentage of links in Client-to-Access (C-A)
applications of 40G is 30%, for Access-to-Distribution (A-D) links, it is
30%, and for Distribution-to-Core (D-C)links it is 20%.  While Flatman does
not explicitly provide a relative breakout of link quantities between the
segments, C-A, A-D & D-C, perhaps one can use his
sample sizes as an estimate.  This yields for C-A 250000, for A-D 16000 and
for D-C 3000.  Combining with the above adoption percentages yields an
expected link ratio of C-A:A-D:D-C = 750:48:6.
Perhaps Alan Flatman can comment on how outrageous this appears.<


The primary purpose of flatman_01_0108 was to establish length
distributions for C-A, A-D and D-C links in the enterprise data centre.
Slide 11 records the presence of Ethernet speeds when the survey was
conducted in 2007 plus anticipated deployment for 2010 and 2012. Slide 11
data simply shows if any speed is present or not (it could be a single link
in an installation!). It does not imply any penetration level. I included
slide 11 to observe a speed trend and it should not be used for any other

I've been watching the reflector traffic with considerable interest and
would like to clarify some of the data contained in flatman_01_0108.
99.175% of all links in this survey were under 100m. If I exclude C-A links
under 10m, and assume they are implemented in copper, then 98.8% of all
remaining links will be under 100m. I have calculated link capture rates up
to 300m for both scenarios, expressed as %ages of total links. My
assumption here is that the same extended reach MMF solution would be used
from 10m up to its maximum reach. Please see the attached.

I have also calculated 40G and 100G port volumes based on hayes_01_0407
(revised in the HSE tutorial of Nov 2007), noting the contributions of
extended reach in 25m increments over time. I haven't quite finished the
graphics for this yet.

Questions or comments welcome.

Best regards,   Alan

Attachment: Data Centre Links vs. lengths for XR ad hoc.pdf
Description: Binary data