AW: Comparison between sampled SFlow and Interface-Statistic

Hi Christian,

the difference is too much !

Regards,

Alexander

-----Urspr|ngliche Nachricht-----
Von: Christian Hammers [mailto:ch@westend.com]
Gesendet: Dienstag, 7. August 2007 14:58
An: Alexander Czutka
Cc: sflow@sflow.org
Betreff: Re: [sFlow] Comparison between sampled SFlow and Interface-Statistic

On Tue, Aug 07, 2007 at 04:19:14AM -0700, Alexander Czutka wrote:
> a customer of mine is complaining about the difference between the data
> which he samples with SFlow and SNMP.

Be aware that SNMP ifInOctets also counts the Ethernet and IP header
so small differences are to be expected.

> I put a single switch and transferred traffic between a client and a
> server. Then I compared the amount of sflow-data with the
> interface-values.
>
> (I changed the polling and sampling interval to 1). There was a gap of
> 50 % when I transferred 500 Mbytes.

IIRC, sFlow is, like NetFlow only enabled on input interfaces whereas
SNMP usually queries incoming and outgoing bytes from one interface.
Maybe this explains the "exactly" 50%.

So what you was supposed to do was to account the incoming traffic on the
switch uplink port and the incoming traffic on the switch' customer port
with netflow and in the other test incoming and outgoing traffic of just
the customer port with SNMP.

bye,

-christian-

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