95th Percentile Bandwidth Monitoring

Kenneth Burgener kenneth at mail1.ttak.org
Tue May 26 21:17:31 MDT 2009

Many data centers bill on the 95th percentile.  Might anyone have a 
suggestion for a good 95th percentile bandwidth monitoring tool?  I 
would prefer one that will take 5 minute snapshots and dump the bit 
rates to a database (the 5 minute interval would also closely match the 
interval to which data centers sample bit rates).  This would enable me 
to programmatically trigger other events.  My firewalls are all Linux 
based iptables systems (fronted with Shorewall).

I would like to be able monitor our data usage, to make sure we keep our 
95th percentile at an acceptable level so we don't break the bank.  I 
would like to eventually have an automated script that will trigger, if 
our usage is high for the month, and throttle our bandwidth down.

I thought about screen scraping the reports the data centers generate, 
but I ran into a few snags.  One data center has a reporting tool, but 
it is too full of ajax to make screen scraping a viable option.  The 
other data center does not have an online reporting tool, but will 
generate reports on demand.

I then found a list of many Linux based bandwidth monitoring tools, but 
they all work like "top" and are not any good at giving me sampled data 
at any interval.  Then I thought about screen scraping TX/RX bytes from 
"ifconfig", but I found out that the counters rolls over and the output 
is not very consistent, which made screen scraping very ugly.  I next 
found vnstat has a timed traffic monitor, which I ran ever 5 minutes for 
5 seconds, screen scraped the kB/s, which gave gave me more what I was 
looking for, but I still think it is a pretty ugly hack.  I am really 
hoping to find a tool that will output what I am looking for in such a 
way that I don't have to screen scrape it.

I also would like to generate reports, so I looked at Cacti, but this 
appears to need to be pointed to an SNMP source.  I saw a few mentions 
of running an SNMP service on the Linux server.  Would that get me the 
bit rates I am looking for?

Any suggestions?


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