Simulate slow network connections on Linux and Mac OS X

!Linux
!OSX
!Docker

Inspired by tylertreat/Comcast, the connectivity setting in the WPTAgent and sltc.

Throttle uses pfctl on Mac and tc on Linux to simulate different network speeds. On Linux you also need ip for Throttle to work (install using sudo apt-get install -y net-tools).

You can set the download/upload speed and/or RTT. Upload/download is in kbit/s and RTT in ms.

Use with latest NodeJS LTS.

Install

``
npm install @sitespeed.io/throttle -g
`

On OSX, add these lines to `/etc/pf.conf` if they don't exist, to prevent the `pfctl: Syntax error in config file: pf rules not loaded` error when you try to run throttle

`
pf_enable="YES"
pflog_enable="YES"
`

On Linux you need to make sure ip and route is installed (install using sudo apt-get install -y net-tools).

Start simulate a slower network connection

Here is an example for running with 3G connectivity. Remember: Throttle will use sudo so your user will need sudo rights.

`
throttle --up 330 --down 780 --rtt 200
`

Pre made profiles

To make it easier we have pre made profiles, check them out by throttle --help:

`
--profile Premade profiles, set to one of the following
3g: up:768 down:1600 rtt:150
3gfast: up:768 down:1600 rtt:75
3gslow: up:400 down:400 rtt:200
2g: up:256 down:280 rtt:400
cable: up:1000 down:5000 rtt:14
dsl: up:384 down:1500 rtt:14
3gem: up:400 down:400 rtt:200
4g: up:9000 down:9000 rtt:85
lte: up:12000 down:12000 rtt:35
edge: up:200 down:240 rtt:35
dial: up:30 down:49 rtt:60
fois: up:5000 down:20000 rtt:2
`

You can start throttle with one of the premade profiles:

`
throttle --profile 3gslow
`

or even simpler
`
throttle 3gslow
`

Add packet loss

By default there's no packet loss. That is by design: If you want to use Throttle and have the same network speed, packet loss is no good. However if you want to simalate a really crappy network you probably want to add packet loss. You do that with the --packetLoss option. You set the packet loss in percent.

`
throttle --profile 3gslow --packetLoss 5
`




Use a configuration file


You can also use a configuration file with your settings. Use --config to map your config file to throttle.

config.json
`json
{
"up": 330 ,
"down": 200,
"rtt": 1000
}
`

And then run:
`
throttle --config config.json
`

Stop simulate the network

Stopping is as easy as giving the parameter stop to throttle.

`
throttle --stop
`

or

`
throttle stop
`

Add delay on your localhost

This is useful if you test a local web server or run WebPageReplay and want to add some latency to your tests.

`
throttle --rtt 200 --localhost
`

Stop adding delay on localhost

`
throttle --stop --localhost
`

Use directly in NodeJS

`javascript
import throttle from '@sitespeed.io/throttle'
// Returns a promise
throttle.start({up: 360, down: 780, rtt: 200}).then(() => ...
`

or

`javascript
import throttle from '@sitespeed.io/throttle'
// Returns a promise
const options = {up: 360, down: 780, rtt: 200};
await throttle.start(options);
// Do your thing and then stop
await throttle.stop();

`

Log all commands


You can log all the commands that sets up the throttling by setting LOG_THROTTLE=true.

`
LOG_THROTTLE=true throttle 3gslow
`

or

`
throttle 3gslow --log
`

Run in Docker (on Linux)

Make sure to run `sudo modprobe ifb numifbs=1` before you start the container.

And then when you actually start your Docker container, give it the right privileges with `--cap-add=NET_ADMIN``.