NETWORK-TESTING.md

Network testing guide

This guide includes various network testing methods and tips for Westiny.

Simulating network behavior (linux only)

Nowadays we have so good internet connections, sometimes it is hard to really test or reproduce a given network-related bug. Fortunately, Linux has a nice tool for traffic control since ages: tc

Latency, packet loss, reordering (netem)

Add latency to localhost, only for a given port: (Source: https://stackoverflow.com/a/40203517)

It will add an emulated 300ms latency for every packet that arrives at port 5745 (both TCP and UDP), but it lets through any other packet.

sudo tc qdisc add dev lo root handle 1: prio priomap 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
sudo tc qdisc add dev lo parent 1:2 handle 20: netem delay 300ms
sudo tc filter add dev lo parent 1:0 protocol ip u32 match ip dport 5745 0xffff flowid 1:2

Removal of the rule:

sudo tc qdisc del dev lo root

For detailed emulated network behaviors see netem's documentation, but a few example:

• Add delay with variation of +-50ms: netem delay 300ms 50ms
• Add packet loss: netem loss 1% (every 100th packet will be dropped on average)

How to add multiple netem rules?

TODO