Simulate a slow network connection on Mac OS X

January 14th, 2014 12:28 – by Torsten Trautwein

Testing how a website, app, service, etc. reacts to a slow and/or unstable network connection is pretty straightforward on OS X. This is very useful to especially simulate mobile connections which sometimes have a low bandwidth, high latency, or drop network packages altogether.

To make your connection sloppy, you can utilize ipfw pipes which is provided by Mac OS X 10.9 Mavericks. Open up your favorite Terminal app and use the following commands:

Show all existing rules

sudo ipfw list

Configure pipe to add some latency

sudo ipfw pipe 1 config delay 200ms

Configure pipe to have a limited bandwidth

sudo ipfw pipe 1 config bw 30KByte/s

Configure pipe to randomly lose half of the packets

sudo ipfw pipe 1 config plr 0.5

You can also set multiple options for a pipe

sudo ipfw pipe 1 config delay 500ms bw 100KByte/s plr 0.2

Use the configured pipe for all IP traffic

sudo ipfw add 1 pipe 1 ip from any to any

Remove the pipe and its configuration to reset everything you set up

sudo ipfw pipe 1 delete
sudo ipfw delete 1


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Torsten Trautwein
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