Throttling Network Programmatically on Ubuntu 18.04

When testing distributed systems, sometimes it is necessary to find out the network tolerance before production deployment.

Network simulation in essence involves 3 parts

1. Latency
2. Bandwidth
3. Packet loss

Setup

The following assumes you have two nodes set up

1. server
2. client

Latency

Before starting any tests, it is good to get a benchmark of your current setup.

From your client node run

ping <server-ip-address>

Now let's add a 500ms latency

# tc qdisc add dev eth0 root netem delay 500ms

If you run ping again, you will get a different result

Let's say we want to add some variance to the latency

Here we add a 10ms variance along a normal distribution in addition to the 500ms latency

Notice the use of  change instead of add

tc qdisc add dev eth0 root netem delay 500ms 10ms distribution normal

Packet loss

The following line adds a 10% packet loss in addition to a 250ms delay

tc qdisc change dev eth0 root netem loss 10% delay 250ms

Note: These changes do not persist across restarts

Bandwidth

Using Wondershaper

https://github.com/magnific0/wondershaper

For bandwidth control, you can use wondershaper

After installation you can run the following

wondershaper -a eth0 -u 30000 -d 10000
wondershaper -c -a eth0

Test bandwidth

Use iperf to test if bandwidth limitations are applied

On the server run iperf -s to start the server

On the second node run iperf -c <server-ip-address>