Setting up AQM - THIS PAGE IS DEPRECATED for current builds of CeroWrt

If you are using CeroWrt 3.10.24-8 (December 2013) or newer, Use the SQM setup instructions at:

If you’re using the older CeroWrt 3.8.8-4, you should definitely upgrade to the current version. It offers much better performance, more features, and better stability. Nonetheless, here’s the info about the new Network/SQM tab built into the GUI. If you just want to try out CeroWrt:

  • Set the Queuing discipline to “fq_codel”
  • Set the Queue setup script to “simplest.qos”
  • Set the up and download speeds to something less than the full rated speed of your internet provider. Entering a value that’s 85% of the full speed (in each direction) is definitely safe.

If you want to experiment, try different queueing disciplines or setup scripts, or set the link speeds to a higher percentage and the run tests to see when the latency starts to get worse.

If you’re using a 3.7 or earlier build

CeroWrt defaults to using the Active Queue Management that comes from OpenWrt. It’s pretty good. But CeroWrt provides a script that’s better in that it uses smaller quantums and supports ipv6 fully. You need to edit three files, then restart the router to invoke it.

1. Edit the file to match your actual bandwidth up and down. To do this, edit the file at /usr/sbin/, and find the two lines below. Change the numbers to match your link’s speed. NB: The numbers are in kbps (e.g., indicate a 3 megabit link with 3000; 768kbps with 768, etc.)

If you are using some forms of ADSL, you will also need to fiddle with the overhead figure to calculate in the ATM overhead.


2. Edit the /etc/rc.local file by adding the following line before the last line (exit 0):


3. Edit the /etc/hotplug.d/iface/00-debloat file by adding the following line to the “ifup” stanza. 

[ "$DEVICE" = "ge00" ] && /usr/sbin/

It will look something like this when you’re done:

[ "$ACTION" = "ifup" ] && {
     IFACE=$DEVICE QMODEL=nfq_codel_ll /usr/sbin/debloat >> $DEBLOAT_LOG 2>> $DEBLOAT_LOG2
     [ "$DEVICE" = "ge00" ] && /usr/sbin/

4. Restart your router, and the will take effect.

We do plan to make this available as a gui option in the future, unless it gets ported into C.

Note that we default to about 5% reserved for “background traffic”. In practice it appears reserving 20% or so is closer to correct, and you can fix that by going into /usr/sbin/debloat and changing in the egress function the background traffic calculation to be 16 rather than 19.

To edit this page, submit a pull request to the Github repository.
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Network Performance Related Resources

Jim Gettys' Blog - The chairman of the Fjord
Toke's Blog - Karlstad University's work on bloat
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Candelatech - A wifi testing company that "gets it".