What does 95th %tile mean?

Geoff Huston gih at telstra.net
Thu Apr 19 22:03:02 UTC 2001

The 95% reading always struck me as a randomly generated number in any case.

Take an extreme example - a customer operates a wire such that both in and 
out are at line rate for five minutes, and then both in and out are idle 
for five minutes, continually.

Depending on the synchronization between the burst pattern and the sampling 
system, and the sampling technique itself, the 95% reading can be zero, 
half the line rate, or the line rate, and all answers are equally valid in 
some sense.

While real situations do not exhibit such a large range of potential 
variability (i.e. 100%), there is still a hefty level of variation in a 95% 
reading due to the interactions between the time base of the traffic, the 
time base of the meter engine and the sampling technique used by the meter 

It leads to the situation where the provider confidently asserts that the 
95% value was xkbps, and the customer confidently asserting ykbps and both 
readings are equally valid, with both measurements using the _same_ 
measurement technique. How is the consequent billing dispute resolved _fairly_?

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