Re: Pricing model for transit services

[Joe Abley <jabley () isc org>]

On Mon, Sep 23, 2002 at 04:07:47PM -0400, Richard A Steenbergen wrote:
> On Mon, Sep 23, 2002 at 12:50:17PM -0700, Lane Patterson wrote:
>
> > And there are at least 4 ways of computing 95th percentile, though I'm sure
> > there've already been threads on this.
>
> There is only one way, anyone else is computing "something else" that they 
> just happen to bill with. But this sounds like a subject for the NANOG 
> FAQ. :)

I think the problem is not that there are multiple definitions of
how to calculate the 95th percentile of a sample population, but
that different peoples' sample populations are constructed in
different ways.

I have seen billing based on:

  max(95th(to_cust), 95th(from_cust))
  95th(max(to_cust, from_cust))
  95th(to_cust + from_cust)
  95th(to_cust)

all referred to by different people as "95th percentile billing".
There are also many different ways of obtaining values for "to_cust"
and "from_cust", just to keep things interesting.

I would be interested to find out how many customers of services
billed by "95th percentile" do their own measurements and compare
them with the bill. I suspect the number is not large.

Maybe that's why most providers don't find it necessary to spell
out exactly what calculations they are doing in order to arrive at
a monthly figure with a dollar sign in front of it.


Joe