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Re: Simulator for slow Internet connections



Thus spake John Case (case@xxxxxxxxxxxxxxxx):

> On Wed, 1 Dec 2010, Maciej Zbierski wrote:
> 
> >I was going through the "Coding Projects" site the other day and spotted
> >that Tor is in need of a simulator for slow connections. I have written
> >something similar as a part of my M.Sc., so I thought I could contribute by
> >adapting my code to Tor's needs. First of all, has there been any progress
> >on the subject (so that I don't double someone's work)?
>
> Why is this a coding project ?  Why don't they just use FreeBSD with 
> dummynet ?

I've personally used Linux's NetEM for testing my Tor Circuit Build
Timeout learning code:
http://www.linuxfoundation.org/collaborate/workgroups/networking/netem

It worked well but it has a major drawback in that if you use netem on
the same machine as your code is running, you can't do real packet
loss simulations because the Linux networking stack hints to the TCP
layer that the loss was artificial so that window sizes are not
adjusted as they would be in reality:
https://www.linuxfoundation.org/collaborate/workgroups/networking/netem#Caveats

Getting a patch to disable this behavior would be a great help.


Otherwise, I think we need to revise this task on our website to say
that we're looking for a Tor network simulator, not a slow network
simulator. Easy mistake, I guess ;)


-- 
Mike Perry
Mad Computer Scientist
fscked.org evil labs

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