95th Percentile Bandwidth Monitoring

Lance Grover lance.grover at gmail.com
Wed May 27 10:34:23 MDT 2009

Use cacti or a simple mrtg setup.  net-snmp is the package for the snmp
service, to make it really easy for yourself your /etc/snmp/snmpd.conf file
can look like this:
rocommunity public
that way any service can query the snmp service with the comunity string of
public and get the information (interface traffic and other information),
then just configure your firewall to limit the access to the snmp service
port of 161.  That should get you going quickly.

On Tue, May 26, 2009 at 9:17 PM, Kenneth Burgener <kenneth at mail1.ttak.org>wrote:

> 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?
> Thanks,
> Kenneth
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Lance Grover

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