[e2e] Simulator for wireless network

[Detlef Bosau]

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.

In addition, there are always two ways to produce wrong results.

The first is: Simulate. As you never know, what you´re simulating, your 
results will be wrong for sure.
The second is: Conduct real experiments. As you never know, what you´re 
really doing, your results will be wrong for sure.

So, the best way is, and somewhere I heard this were an old jiddish 
saying: If you have only two impossible choices, choose the third.

So, in my opinion, you should have a very precise idea what you want to 
find out, either by real experiments or by simulation.
Some questions are:

- are you interested in 802.11 networks?
- are you interested in cellular networks?
- is mobility (beyond pedestrian) allowed in your network?
- which design questions are not yet fully discussed?

I´m writing an RLP agent for the NS2 myself at the moment and I have 
much more questions than answers here.
And I´m often quite upset, when I read "papers" which refer to "well 
known simulators" and present some funny tables and columns of numbers, 
called "results" and it´s in fact not even clear, which question is 
actually answered.

One basic lessen, I´ve always learned from dealing with mobile networks 
/ wireless networks and the like:
Even the best answer is at least as bad as the question.

Why I choose the NS2: It´s quite easy. I´m quite familiar with the NS2 
and it´s widely accepted. And because I´m quite familiar with the NS2, 
it´s quite easy for me to add new classes and protocols there and I´m 
well aware of a huge number of pitfalls which are around nearly each 
corner. E.g. the first time, you get a null pointer exception or 
segmentation violation or something like that will cause you a nightmare 
of debugging the code day and night in the debugger - o.k., this 
afternoon I consumed a "one way event" with delete instead of free, but 
after some hours, I remembered I did something simular some years ago 
and looked at my own old source code - which solved the problem.
(As you can imagine, I got some funny error messages before ;-))

If you´re completely new to simulation and have the time, you will 
perhaps start with the NS 3. I don´t know.

But first of all: You should make perfectly clear, what you want to 
simulate and what´s your precise question.
Because good questions are often more than half the answer.

Detlef

-- 
Detlef Bosau
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70565 Stuttgart
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