Seems like it would be simple - multiply rx stats by sample rate before
storing/graphing?  I don't do much development so who knows.

 

I would maybe try without sampling, but maybe set your active/inactive
timers to 120/60?  It's not as real-time as it could be, but if you have
a ton of dynamic traffic it will slow down the flow rate.

 

I'm only seeing traffic of around 100Kpps, but I'm on an old P-III and
it's only using 25% during peaks.  Surely a fast box can keep up with
netflow exports from really high util - unless every packet is a
different "flow" - like during some sort of DoS attack.

 

G

 

________________________________

From: [email protected] [mailto:[email protected]] On Behalf Of
Kyle McLerren
Sent: Thursday, February 12, 2009 4:03 PM
To: [email protected]
Subject: Re: [Ntop] Ntop NetFlow Question

 

Thanks for the response. We are doing a boat load of traffic. We had to
enable sampling because our previous collector could no longer cope with
the sheer volume of flows it was trying to process. I do admit I dont
know if ntop can process the flows better as I just started to use it.
Previous we were using flow-tools and flowscan/cuflow. I should not have
said "accurate," as they are prefectly accurate. It just others get
confuse when looking at them and it gets old telling people to keep in
mind the data is accurate, its just the numbers are "smaller" then they
actually really are :)

so it looks like the answer is no, there isnt a way to set the sample
rate.. seems like a really basic and easy feature to implement, would be
great to see it!

thanks again.

On Thu, Feb 12, 2009 at 1:54 PM, Gary Gatten <[email protected]>
wrote:

How'd anyone ever function without Google?

 

http://www.mail-archive.com/[email protected]/msg11605.html

 

 

 

________________________________

From: [email protected] [mailto:[email protected]] On Behalf Of
Gary Gatten
Sent: Thursday, February 12, 2009 3:49 PM
To: [email protected]
Subject: Re: [Ntop] Ntop NetFlow Question

 

I have seen this asked and I think answered a couple times, but since I
don't do sampling I wasn't paying much attention.  I'm sure if you
searched the list you'd see some answers from Luca and/or Burton.  I
searched the FAQ and man page and couldn't find anything.  Also checked
the "Preferences" and couldn't see anything there either.  MAYBE check
the globals-define.h; there's lots of cool stuff in there but you have
to recompile with changes :-(

 

Of course the easy answer is to NOT sample.  Unless you have a $HIT load
of traffic it will be OK, especially if you set the active/inactive
export timers to something reasonable.

 

BTW: What is "not accurate"?

 

 

 

________________________________

From: [email protected] [mailto:[email protected]] On Behalf Of
Kyle McLerren
Sent: Thursday, February 12, 2009 3:13 PM
To: [email protected]
Subject: [Ntop] Ntop NetFlow Question

 

Hi All,

Im sure this has been answered before, but I couldnt find an answer
anywhere. I use sampled netflow, and I simply wanted to know if theres
an option with the ntop netflow plugin to configure the sample rate?
Otherwise, my results arent acurate. Im sending 1 out of 100 from my
router.

thanks!

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