[j-nsp] cflowd sampling

From: Przemyslaw Karwasiecki (karwas@ifxcorp.com)
Date: Wed Nov 07 2001 - 11:46:08 EST


All,

I am looking for some more detail descriptions how traffic sampling
really work.

I have just setup cflowd with 'rate 100' 'and run-length 1',
and the results given by cfdnexthops are far different from
what I would expect. Specifically traffic reported by this utility
is approximately 2% of traffic which is actually send over each
of the next hops.
Because of rate ratio and run-length, I would expect to see 1%
of traffic to be reported.

Also, cflowd is actually meant to work on flow data, and I don't
understand how you can identify full flows, from SYN/ACK to FIN
just by looking at every 100ths packet. Or I am missing something.

Any help, pointers, suggestions, explanations will be greatly appreciated.

TIA,

Przemek



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