Contention/Oversubscription maths

David Swafford david at
Fri May 27 02:21:28 UTC 2011

Hi Adam,

>From the perspective of an enterprise customer, if we're talking
strictly Internet circuits, you're over-subscription estimates seem
very conservative to me.  On our 100mb/s Internet circuits, our
average utilization is about 40mb/s down and 15-20mb/s up on any given


On Thu, May 26, 2011 at 6:48 PM, Adam Armstrong <lists at> wrote:
> 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)?
> Thanks,
> adam.

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