Network Properties Simulation Using qdisc

If you ever want to simulate bad transmission conditions (packet loss, latency, bandwidth, …) in a network: there is a module built-in to the linux kernel named qdisc. More information can be found on tldp.org.

 

Examples

Add delay 80ms

tc qdisc add dev eth0 root netem delay 80ms

Add delay with +-10ms jitter

tc qdisc add dev eth0 root netem delay 80ms 10ms
NB: For very large jitter, package order will be changed by netemIn order to disable this:
tc qdisc add dev eth0 root handle 1: netem delay 10ms 100ms

tc qdisc add dev eth0 parent 1:1 pfifo limit 1000

Add loss etc

tc qdisc add dev eth0 root netem delay 10ms 1ms distribution normal loss 2% duplicate 0.1%

Show current parameters

tc qdisc show dev eth0tc filter show dev eth0 

More complex example:

Consider you have a machine connected on eth1 and eth2 in your network, which will be used to simulate the network conditions:
d1=eth1

d2=eth2
tc qdisc add dev $d1 root netem delay 50ms 2ms distribution normal loss 0.5% duplicate 0.1%
tc qdisc add dev $d2 root handle 1:0 htb default 15
tc class add dev $d2 parent 1:0 classid 1:1 htb rate 400mbit ceil 400mbit

 

Reset

Once you are done you may want to remove the filters again:
tc qdisc del dev eth0 root
tc qdisc show