Simulate single big network delay and packet burst after
I’m testing the Opus codec and VoIP stack which uses it.
I have synthetic test utility which sends internally Opus RTP traffic between two ports on loopback interface + this writes resulting audio to files to allow further analysis.
Using Linux ‘tc’ utility I can simulate various network impairments.
However I stuck to simulate such thing like "sudden network lag". Sorry for my poor English !
This should look like network is stopped for 1 seconds and after all delayed packets are sent as soon as possible to their targets.
Is it possible to implement with ‘tc’ utility ?
I tried to run the ‘tc’ command to make delay 1000ms during the synthetic test process; but it doesn’t give me wanted effect.
May anyone to give advice ?
Thank you 🙂
This should look like network is stopped for 1 seconds and after all
delayed packets are sent as soon as possible to their targets.
That is actually possible … From man tc:
netem
Network Emulator is an enhancement of the Linux traffic
control facilities that
allow to add delay, packet loss, duplication and more other characteristics to
packets outgoing from a selected network interface.
… and from man tc-netem:
slot
defer delivering accumulated packets to within a slot.
Each available slot can be configured with a minimum delay to
acquire, and an optional maximum delay.
… So, you can do something like this:
sudo tc qdisc add dev interface root netem slot 1000ms 1000ms
… where interface is your intended network interface name as shown in e.g. the output of ip a.
That will hold all transmitted packets on the specified interface for 1000ms and then release them all at once (in a burst).
Notice that delay on the other hand will add a delay of 1000ms to every transmitted packet on the specified interface.