Network Simulation

Linux Network emulator linuxfoundation

Delay all packets out eth0

   # tc qdisc add dev eth0 root netem delay 100ms

Delay + 10ms variation, each 25% correlated to previous value.

   # tc qdisc change dev eth0 root netem delay 100ms 10ms 25%

Other options
- loss 0.3% 25% (% loss and correlation)
- duplicate 1%
- corrupt 0.1% << corrupts single bit

Rate control

There is no rate control built-in to the netem discipline, use Token Bucket Filter (TBF) to limit output.

 # tc qdisc add dev eth0 root handle 1:0 netem delay 100ms
 # tc qdisc add dev eth0 parent 1:1 handle 10: tbf rate 256kbit buffer 1600 limit 3000
 # tc -s qdisc ls dev eth0
 qdisc netem 1: limit 1000 delay 100.0ms
   Sent 0 bytes 0 pkts (dropped 0, overlimits 0 )
 qdisc tbf 10: rate 256Kbit burst 1599b lat 26.6ms
   Sent 0 bytes 0 pkts (dropped 0, overlimits 0 )

To check status
```
 tc -s qdisc
```
To remove the delay from eth0
```
 tc qdisc del dev eth0 root
```

Here is a simple example that only controls traffic to one IP address.

 tc qdisc add dev eth0 root handle 1: prio
 tc qdisc add dev eth0 parent 1:3 handle 30: netem \
     delay 200ms 10ms distribution normal
 tc qdisc add dev eth0 parent 30:1 tbf rate 20kbit buffer 1600 limit 3000
 tc filter add dev eth0 protocol ip parent 1:0 prio 3 u32 \
    match ip dst 172.17.34.0/24 flowid 10:3