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: http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_SQM_for_CeroWrt_310

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 simple_qos.sh 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 simple_qos.sh file to match your actual bandwidth up and down. To do this, edit the file at /usr/sbin/simple_qos.sh, 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.

UPLINK=2000
DOWNLINK=20000

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

/usr/sbin/simple_qos.sh

[ "$DEVICE" = "ge00" ] && /usr/sbin/simple_qos.sh

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/simple_qos.sh
}

4. Restart your router, and the simple_qos.sh 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 ¹⁄₆ rather than ¹⁄₉.