Contention/Oversubscription maths

Adam Armstrong lists at
Thu May 26 22:48:48 UTC 2011

Hi All,

Do any of you have any pointers on how to go about predicting usage for 
high-speed ethernet access?

I'm running 1GE links into buildings, and hanging many (100-1000) 100M 
customers off switches in the basement, simple enough.

I'm assuming ~300Kbps average peak usage per customer, but I can't quite 
work out at what point that number becomes more important than the fact 
that each user can peak at 100mbit (and that the backhaul is only 
access-speed * 10).

I'm well versed in the economies of scale of fitting 10,000 8mbit 
customers into 1GE, but this seems altogether a different beast to 
predict. If any of you have similar scenarios I'd be very interested to 
hear on/off list :)

Finally, what do people think of selling a 1G service with 1G backhaul 
(and potentially 10s or 100s of customers buying this service alongside 
n*100s of customers with 100M service)?


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