95th Percentile != Lame

Mon Jun 4 03:10:58 UTC 2001

On Sun, Jun 03, 2001 at 07:42:13PM -0700, David Klindt wrote:
>
> > I still fail to see how "peak bits" or "bursted bits" are more
> > expensive than "regular bits".  A 100Mbit FE port costs whatever it
> > costs, and does not fluctuate with usage.  This is true of almost all
> > of your links within the network - excluding those where you have
> > negotiated usage-based billing.  An OC3, point to point, costs as much
> > as it costs irrelevant of its usage.  Therefore, every bit that
> > crosses this circuit has a cost.
> >
> > Why not simply pass this cost on to the customer bit for bit?
>
> It is NOT that the each bit has the same cost - it is the cost of
> maintaining enough EXTRA bandwidth so that the downstreams do not
> bounce up against the ceiling. That amount is basically covered by
> using the 95 rule.

But peak vs non-peak has little to do with 95th percentile. Assuming that
every day's traffic patterns are the same (which is rarely true, there is
almost always a weekend/sunday difference), 95th percentile removes the
top 1 hour 12 minutes from each day's peak. This is more then enough time
to piss off your customers if they all hit the peak together and congest
your network.

If you really wanted to motivate customers to not all burst above what you
have provisioned, you would charge them a "bursting fee". Personally I am
of the philosophy that it is easier to build your network right. With the
availability of cheap dark fiber, cheap wdm gear, and "carrier neutral
exchange points" like PAIX and Equinix, the problem of "Oh crap my OC12 is
full during peak times, it will be another 6 months before the telco can
get me another one and it will double my operating costs" can be worked
around. If you build a good network which is really scaleable, bursting
costs you nothing. If you can pass the savings on to customers, while
giving them a solid network, you will get more customers who WANT to push
traffic. Pushing traffic leads to billing, which leads to money (usually).

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
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