Re: Simulating (emulating?) bad network conditions

If you want terribad network conditions, you can use cellsim 
(instructions at http://alfalfa.mit.edu/) which will let you replay actual 
network condition traces from cellular links (including such awesome 
properties as intermittent 60+s latency).

--Quentin

On Sat, 23 May 2020, Jehan Tremback wrote:

> Yes, we have used tc netem to successfully make a connection bad.
>
> --
>  Jehan Tremback
>  [email protected]
>
> On Sat, May 23, 2020, at 1:22 PM, Erik Auerswald wrote:
>> Hi,
>>
>> recently someone asked about a script for simulating or emulating degraded
>> network conditions.  I could not provide an answer, because I do not have
>> something like that available, yet.
>>
>> But I have just read about "Comcast" which seems to do just that:
>> https://github.com/tylertreat/Comcast
>>
>> The README.md contains information on how to use iptables and/or tc
>> directly instead of through Comcast as well:
>>
>> """
>> Linux
>>
>> On Linux, you can use iptables to drop incoming and outgoing packets.
>>
>>     $ iptables -A INPUT -m statistic --mode random --probability 0.1 -j DROP
>>     $ iptables -A OUTPUT -m statistic --mode random --probability 0.1 -j DROP
>>
>> Alternatively, you can use tc which supports some additional options.
>>
>>     $ tc qdisc add dev eth0 root netem delay 50ms 20ms distribution
>> normal
>>     $ tc qdisc change dev eth0 root netem reorder 0.02 duplicate 0.05
>> corrupt 0.01
>>
>> To reset:
>>
>>     $ tc qdisc del dev eth0 root netem
>> """
>>                 -- https://github.com/tylertreat/Comcast#linux
>>
>> I have not tested this, but it seems to provide a starting point for
>> experimentation.
>>
>> HTH,
>> Erik
>> --
>> To a first approximation, we can say that accidents are almost always
>> the result of incorrect estimates of the likelihood of one or more things.
>>                         -- C. Michael Holloway, NASA
>>
>