https://github.com/derhuerst/simulate-network-conditions
Simulate lossy or high-latency network conditions.
https://github.com/derhuerst/simulate-network-conditions
latency network nodejs packet-loss
Last synced: 3 months ago
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Simulate lossy or high-latency network conditions.
- Host: GitHub
- URL: https://github.com/derhuerst/simulate-network-conditions
- Owner: derhuerst
- License: isc
- Created: 2020-05-25T01:31:52.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2020-05-30T22:56:08.000Z (about 5 years ago)
- Last Synced: 2025-04-15T05:02:14.313Z (3 months ago)
- Topics: latency, network, nodejs, packet-loss
- Language: JavaScript
- Size: 16.6 KB
- Stars: 5
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: readme.md
- License: license.md
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README
# simulate-network-conditions
**Simulate [lossy](https://en.wikipedia.org/wiki/Packet_loss) or high-latency network conditions.** Like the [throttling option in the Chrome/Chromium DevTools](https://developers.google.com/web/tools/chrome-devtools/network#throttle).
[](https://www.npmjs.com/package/simulate-network-conditions)
[](https://travis-ci.org/derhuerst/simulate-network-conditions)
[](https://gitter.im/derhuerst)
[](https://github.com/sponsors/derhuerst)
## Installation
```shell
npm install simulate-network-conditions
```
## Usage
Let's simulate an unreliable transport protocol (like UDP, unlike TCP) over a bad 2G connection:
```js
const {pipeline} = require('stream')
const simulate = require('simulate-network-conditions')
const signalStrenth = t => t % 20_000 / 20_000
const lossy = simulate.lossByTime((t, i) => {
if (signalStrenth(t) <= .3) {
// packet loss from now on, for 3s
return {from: t, length: 3000}
}
return null // no packet loss
})
const slow = simulate.latency(() => {
const s = signalStrenth(Date.now())
const jitter = Date.now() % 100 / 100
return Math.floor((6 + jitter - s) * 50)
})
// A -> 2G network -> B
pipeline(peerA, simulate(lossy), simulate(slow), peerB)
// B -> 2G network -> A
pipeline(peerB, simulate(lossy), simulate(slow), peerA)
```
`simulate()` returns a [transform stream](https://nodejs.org/docs/latest-v10.x/api/stream.html#stream_class_stream_transform) in [object mode](https://nodejs.org/docs/latest-v10.x/api/stream.html#stream_object_mode).
The stream only represents *one-way* of network traffic. **If you want two-way network traffic as usually required, use *two* `emulate()` streams and [`duplexer3`](https://www.npmjs.com/package/duplexer3)**:
```js
const duplexer = require('duplexer3')
const aToB = simulate([ /* … */ ])
const bToA = simulate([ /* … */ ])
// A end of the connection
const aEnd = duplexer3(aToB, bToA)
// B end of the connection
const bEnd = duplexer3(bToA, aToB)
```
### packet processors
A
```js
// every packet delayed by exactly .2s
simulate.constantLatency(200)
// jitter: packets randomly delayed by .1-.25s (breaks order!)
simulate.latency(() => 100 + Math.ceil(Math.random() * 150))
// 2% lost (randomly)
simulate.constantLoss(.02)
// 3 packets lost, every 20 packets
simulate.lossByIdx((idx) => ({from: idx + 17, length: 3}))
simulate.lossByIdx((idx, lossPeriodIdx) => {
return {from: lossPeriodIdx * 20, length: 3}
})
// 500ms loss every 3s
simulate.lossByTime(() => ({from: Date.now() + 3_000, length: 500}))
```
## Related
The great [Mininet](http://mininet.org/overview/) [allows you to specify bandwidth, latency & loss](https://github.com/mininet/mininet/blob/dfb297901fd4bf0ad0cad317973180392dafa277/examples/simpleperf.py#L33-L36), and probably works in a much more accurate way. You can use the [`mininet` npm package](https://github.com/mafintosh/mininet) from Node.js.
## Contributing
If you have a question or need support using `simulate-network-conditions`, please double-check your code and setup first. If you think you have found a bug or want to propose a feature, use [the issues page](https://github.com/derhuerst/simulate-network-conditions/issues).