[e2e] Simulator for wireless network
giuseppe.bianchi at uniroma2.it
Sat Apr 14 17:15:36 PDT 2007
At 00.40 15/04/2007, U.Shanker wrote:
>Detlef Bosau wrote:
>>Jeroen Massar wrote:
>>>Durga Prasad Pandey wrote:
>>>>What would be considered the best network simulator(s) for wireless
>>>>networks, particularly for TCP experiments?
>>>A large amount (>40) old laptops spread around a site.
>>>Don't simulate, use real live setups.
>>Unfortunately, that´s not always possible.
And don't neglect the fact that, at least for
802.11 networks (the area which I'm
experimentally more confident), there is a strong
dependence on the network cards / Drivers / OSs
employed. For at least two reasons (at least =
limiting to what I'm personally aware of):
1. it is not granted that ALL cards will exactly
behave as specified by the 802.11 standard (e.g.
some use different CWmin, different EIFS, in
some cases odd behavior do emerge e.g. because of
possible implementation issues)
2. they may also employ proprietary algorithms,
either expected (such as rate adaptation) or, and
this is the case that may really play havoc with
your experiments, unexpected (e.g. one ongoing
finding is that some cards seem to use
undocumented proprietary power control solutions
which you would not nearly expect from a wire-powered device!).
This implies that, in order to have a reasonable
confidence that the experimental trial is
meaningful (at least from a qualitative point of
view, e.g., to assess e.g. dependence from a set
of system parameters), you have to use
homogeneous systems, and it is quite costly to
deploy more than a few identical boards/PCs, with
identical card model and driver version...
Another possibility is to repeat the experiment
with different HW/SW and HOPE that results are
the same. Not only this doubles the cost and
labor, but in many cases this is not even
technically possible (e.g. when your solution
uses some driver-level mechanism or requires
driver modification). In any case, some
care (and, most important, the understanding if
the hardware/software you are using shows some
odd behavior) is needed before taking
conclusions, especially in stressful conditions
(e.g. many terminals, outdoor links).
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