Hello,

I am trying to use nTop to monitor the traffic over my network using SFlow.
I use nTop has a collector for the S-Flow packets sent by my router.
Packet sampling rate is 1 per 512 packets.

The nTop SFlow plugin should be correctly configured as the sFlow collector.

But I get strange results:

For instance, I tried to send a 1 GB file at 1 MB/s on the network. nTop
reports the following :
Stats / Throughput : Current / Peak ~ 2 Kbps
Total Data Sent : 1536 packets = 215.2 KB

I don't understand those results, I was expecting to have:
total_size_sent * sampling_rate = total_size_received_by_ntop

but actually we have here total_size_sent * sampling_rate = 2048 KB
which has nothing to do with total_size_received_by_ntop...

But, if we assume an IP packet size is about 1448 bytes, then we have:
packets_sent  = 1 GB / 1448 bytes

and I observed indeed:
packet_sent * sampling_rate  ~ packets_received_by_ntop

So, why the size (and the speed) is wrong ?

Does anyone here has managed to use ntop with sflow correctly ?
Thanks for your help...

Samuel.


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