Questions about the sFlow plugin

From: Samuel (hdip@laposte.net)
Date: 03/24/03

  • Next message: Marc Lavine: "Re: Questions about the sFlow plugin"

    Hello,

    I am trying to use nTop 2.1.56 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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