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From: Alfred Perlstein <bright@mu.org>
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To: Yuri <yuri@rawbw.com>
Subject: Re: Is it possible to slow down the network interface?
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On 4/2/13 4:25 PM, Yuri wrote:
> For the testing purposes, I would like to be able to control the 
> maximum speed of the interface.
> There is this command 'ifconfig re0 media 10baseT/UTP' that is 
> supposed to lower the speed to 10Mbps. However, it makes interface 
> unusable on my system. All connections are broken, even the router had 
> to be rebooted. Maybe this is the router issue.
>
> Is there any other, "soft" way to change maximum interface speed to a 
> particular value?
> When somebody sends data too fast, OS sends back ICMP notifications 
> that connection is jammed. My question is, is it possible to impose 
> such condition artificially?
> Is 'ifconfig re0 media 10baseT/UTP' actually supposed to work 
> transparently, or disconnects are to be expected?
>

try dummynet, it lets you simulate slow or otherwise special networks.

man 4 dummynet

-Alfred