[mrtg] Re: Business Hours and 95%ile.

Paul C. Williamson pwilliamson at mandtbank.com
Thu Sep 6 22:36:29 MEST 2001

I'm trying to do something like this via the guidance of Alex's FAQ for 
RRDTool (http://faq.rrdtool.org) and getting quite frustrated.  I don't 
want to ignore what goes on at night.  But the problem is that I don't 
want to count the night time "unused" bandwidth.  It's not like my 
company will tell people to work at night instead of during the day 
just to even out the bandwidth usage.  I still want to track it, but I 
want to be able to provide a cgi for looking at just the "business 
hour" usage, versus the 24 hour usage.  Just last week we found 
a disgruntled user transmitting rather large data files from our site without 
his manger's permission.  Upon my suggestion, they monitored what was 
sent out.  Fired the next day.  Now I feel bad, but not as bad as if thisp
 eron would have been successful in what they were trying to do.

Anyone want to collaborate?


>>> Forthofer Russ <Russ.Forthofer at ssfhs.org> 09/06/01 04:22PM >>>

You are probably right that the "business hours only" is not for everyone.
I would agree that in using MRTG to look for anomalies in utilization you
want to look at the whole day.  However, IMHO, there are some cases where it
can be quite helpful to look only at the business day.  For example, if a
line is used primarily during business hours, average utilization across a
24-hour day is pretty meaningless.  Average utilization and 95th percentile
utilization across the business day, however, can be useful statistics,
especially in terms of gathering historical data and tracking growth.  If
the business day "average" is what is being sought (in my case it is), then
simply zeroing out the non-business hours does not resolve the issue, as the
zeroes would skew the average. 


-----Original Message-----
From: Jay Hennigan [mailto:jay at west.net] 
Sent: Thursday, September 06, 2001 2:25 PM
To: Mark Pugh
Cc: mrtg at list.ee.ethz.ch 
Subject: [mrtg] Re: Business Hours and 95%ile.

On Thu, 6 Sep 2001, Mark Pugh wrote:

> I'm currently using MRTG, RRD, and 14all to monitor all my border routers
for bandwidth usage.  I'd like to be able to customize the data collection
and/or reporting to get a business hours (8-5) usage graph and a weekly
95%ile usage graph.  Are there any suggestions?  I've done very little PERL
work before, but can usually manage my way through scripts.  Any help would
be appreciated.

An excellent 95th percentile package is available from


As far as business hours, I'm not sure what you're trying to do.  If you're
calling MRTG from cron, you can edit the crontab to only run it during
business hours.  You'll probably want the unknown-as-zero switch set in
your config file.

IMHO, the business hours idea doesn't seem like a good one for most people.
DOS attacks, viruses, etc. often occur and cause unusual traffic patterns
at all hours.  Generally, it's good to know about such things.  Perhaps RRD
can generate the daily graph with specified begin and end times?

Jay Hennigan - CCIE #7880 - Network Administration - jay at west.net 
NetLojix Communications, Inc.  -  http://www.netlojix.com/ 
WestNet:  Connecting you to the planet.  805 884-6323

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