Sample's sequence number

From: Bao <>
Date: 03/15/05
Message-ID: <>

        Hi everyone,

        For example, we have one of our border routers connected to a peering
point at London (Linx) via our Gigabit port 2/3 (IfIndex : 67).
I would like to analyze the in/out traffic of this port via sFlow.

As Neil McKee suggested, the right algorithm for estimating the frames
from a source X is :

  effective_sampling_rate = delta(sample_pool) / samples_received
  frames(X) = samples_received(X) * effective_sampling_rate

Now, in order to get the samples_received, I try to use the sample's
sequence number, making the difference between the current sequence
number and the last value of it.

We know that the sample sequence number is a 32bits counter which is
incremented with each flow sample generated by a designated source_id.

But the problem is, when I look at the lower 3 bits of the source_id
(unsigned int), I see that it always gets the same value as the "input
port" field so, for example, I can determine how much traffic is coming
in through this port 67 (IfIndex). How can I do to determine how much
traffic is going out through this same port 67 ? Do I have to calculate
it by using the "sample rate" field ?

Received on Tue Mar 15 04:50:43 2005

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