[mrtg] Re: 95th percentile?

Henry Steinhauer H1STEINH at hewitt.com
Fri Sep 24 19:10:55 MEST 1999


It is easy to use Excel to bring in a Log file and then create the
information you are looking for.

Some ISPs use the value in a number of ways.

It is possible to have different bandwidths for each direction of a
connection, thus the 'normal' way of defining this does not work for all

Normal :

1) - taking the highest value of IN or OUT for each interval monitored and
then reporting the 95th percentile level for the "billing interval'

     a - If you are using difrerent bandwidths, this does not work.
     ---  You would need to keep IN and OUT seperate and create it

     b - each ISP has the option to create a different billing interval for
their own purpose
       --  ie - have bills going out each business day so the cash flow is
not just one lump sum.
     --  some on the 5th, some of the 10th, some on the 15th, some on the
20th, some on the 25th.  (all months have these dates).

2) - Another approach is to use the 95% level for Each Day of the MRTG
     --  Since you are gathering this information on a 5 minute interval,
this amounts to 12 per hour or 288 per day.
        --  95% level would then be at the 273.6 value - you could round up
to the 274th or take the 273rd.
     For each day then, you could replace the 'peak' value on the follow on
charts with this value for the monthly and yearly charts.

     This would give you a better feel for how your actual capacity and
performance numbers are going rather than just your billing cycles.
     After all the key is how do you service your users.

     This would be higher than the ISP value on most days, but in general,
you would have a good feel for where you would be on their price sheet and
what you would need to do to keep below certain values.

Any Perl hacks out there ?

I would think that a program that would read the log file daily and then
replace the 'peak' values with the 95th value for the monthly and yearly
sections of the log file would do the trick.  My Perl coding is still not
up to speed, but I have outlined the approach.

I would be willing to work with someone if they want to do the Perl hack as
a sample program.

There is already a sample program to read a set of CFG files so you could
know which targets need to be gathered, or you could require that the list
of log files be put in a file so one could give a list of log files rather
than the entire directory of log files. (I do not need this for all the log
files).  BUT if they really want it for all of them, then just put the
while list in the file to be read.

Suggestions and comments?

Please direct them to Henry Steinhauer   h1steinh at hewitt.com

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