netflow vs pcap

Mike Tancsa mike at
Mon Feb 8 16:01:20 UTC 2010

I am trying to deploy more visibility into parts of my network and 
started to look at netflow.  However, I often find for some 
deployments, I need full pcap headers to see what had been going on.
e.g. customer calls after the fact saying, "~ 36hrs ago, there was a 
'problem'.  Do you know what happened"... Having a full pcap (headers 
anyways) helps a great deal to understand / reconstruct what the site 
was actually seeing.

In my limited foray into netflow, I dont seem to have that level of 
visibility  where I can see how long the 3 way handshake took to 
setup, if ACKs were missed due to packet loss or packets were out of 
order etc etc.

That being said, there are wonderful summary tools in netflow that 
allow you to quickly look for network anomalies.  However, I can 
always export a pcap to netflow format and then use such tools.

Is there a happy medium out there ? What are people using to audit 
network traffic out there ?

Also, what are people using to capture and store netflow data ?


Mike Tancsa,                                      tel +1 519 651 3400
Sentex Communications,                            mike at
Providing Internet since 1994          
Cambridge, Ontario Canada               

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