[Ethereal-users] TCP Stream Analysis - Throughput Graph

["Parsons, John" <John.Parsons@xxxxxxxxxxxxxx>]

Does anyone have more information on how the stats for the throughput graph
are calculated? I've tried searching the site and even digging around the
source and documentation but I can't find any details on the figures in the
graph. Specifically:

The vertical access is labelled [B/s] which I'm assuming is "Bytes per
second" and not "bits per second" (bps), is this correct?
I guessed that this throughput figure was calculated by dividing the size of
the packet in bytes by the "Time delta from previous packet" which would
give a figure in "Bytes per second". But this guess must be wrong as the
figures I get from manual calculations are very different from those graphed
(much too high).
I reckon the delta time between packets is the time it takes for the local
switch to fire the packet out to the host - not the time the packet took to
get from Host A to Host B, this would explain the high figures.

The round trip time graph comes up completely blank for this trace and the
Time sequence (tcptrace) graph gives me an Application Error (NT4!).

I'm about to embark on some capacity planning work and I need to be able to
work out peak throughput (bps) for a large number of systems. The traces
will come from some Distributed Sniffers and I need to know precise
bandwidth requirements per system.

Any advice or information anyone can offer would be greatly appreciated.

John Parsons


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