What does 95th %tile mean?

Richard A. Steenbergen ras at e-gerbil.net
Fri Apr 20 01:37:58 UTC 2001

On Thu, Apr 19, 2001 at 05:18:02PM -0700, David Schwartz wrote:
> > Same algorithm, same raw data, different 95% answers, both valid, yet
> > one is twice as large as the other. Great outcome for a billing
> > system isn't it?
>       Any billing scheme based upon statistical sampling will, with
> some probability, err in the favor of one party or the other randomly.
> But it is important that the customer understands that he is being
> billed based upon statistical sampling and thus there are no "exact"
> measurements.

Fair billing sysems?

The traffic "samples" are just the current value of a byte counter minus
the value of that same counter <x> minutes ago, divided by <x>. If you
wanted to be "fair", you would bill on exact number of bytes transfered.

But on the subject of fair... Most people bill on counters from their
customer aggregation switch, but if you transfer data between two
customers you are billed as though you sent it around the world, how is
this fair? If you send traffic out a paid transit or free peer it costs
you the same, how is this fair? If you pay only the higher of your inbound
or outbound traffic, and you are a web server pushing 100Mbit out, then
you get that 99.9Mbit in if you pay for it or not, how is that fair? How
many people actually count every byte they transfer, and how many ISPs are
actually capable of matching your count with theirs so you know they are
not inflating their numbers either deliberately or accidentally.

Hell, do you think the price you pay is fair? There is a reason major ISPs
dont publish their prices openly, and that is because if you are not
helping some sales person make his Z8 payments or comparison shopping and
demanding better prices, you are probably getting screwed. Some people
will charge for putting you on redundant uplinks with HSRP/VRRP, some will
not. Some people will have redundant diverse well-planned infrastructures
and some will not. Some will charge for both directions and 95th
percentile, some will charge for 1 and 90th percentile. They will all
claim to have better networks then they really do in one form or another,
and they will all hide behind an NDA to make sure you don't find out
because like it or not everyone has some skeleton in their wiring closet.
And yes some will have huge amounts of money yet be run by idiots, and
some will have almost no money and scrape out a solid reliable network.

That is the nature of business, and fair is what you are willing to pay
for the service you get. If you don't like it, vote with your wallet. :P

Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
PGP Key ID: 0x138EA177  (67 29 D7 BC E8 18 3E DA  B2 46 B3 D8 14 36 FE B6)

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