HOWTO

Simplest possible demo

To demonstrate the effect of the fq_codel scheduler, set up a fully saturated network and then observe fq_codel’s effect on ping time latency, as follows.

The effect can be clearly observed with a 10Mbps Ethernet connection:

sudo ethtool -s eth0 advertise 0x002   # restrict to 10Mbps for demo

In a terminal window, run a continuous ping to some other machine on the local network (the other machine does not need to have fq_codel) and leave it running:

ping othermachine

In another terminal window, start up a dd pipe to the other machine to fully saturate the network – you should see the adverse effect on the ping times:

dd if=/dev/urandom | ssh othermachine dd of=/dev/null

Now enable fq_codel – observe the beneficial effect on the ping times – about 30X reduction in latency on a saturated 10Mbps network!:

sudo tc qdisc add dev eth0 root fq_codel

Disable fq_codel and wait a moment for the buffers to get bloated again – the ping times go back up again:

sudo tc qdisc del dev eth0 root fq_codel

Remember to remove the demonstration 10Mbps restriction when you’re all done testing:

sudo ethtool -s eth0 advertise 0xFFF
To edit this page, submit a pull request to the Github repository.
RSS feed

Recent News & Articles

Mar 12, 2017 Wiki page
Make-Wifi-Fast Project
Mar 10, 2017 Wiki page
What Can I Do About Bufferbloat?
Feb 10, 2017 Wiki page
More about Bufferbloat
Dec 27, 2016 Wiki page
RRUL Chart Explanation

Find us elsewhere

Bufferbloat Mailing Lists
#bufferbloat on Twitter
Google+ group
Archived Bufferbloat pages from the Wayback Machine

Sponsors

Comcast Research Innovation Fund
Nlnet Foundation
Shuttleworth Foundation
GoFundMe

Bufferbloat Related Projects

Congestion Control Blog
Lede Project (OpenWrt)
Flent Network Test Suite
Sqm-Scripts
The Cake shaper
AQMs in BSD
IETF AQM WG

Network Performance Related Resources


Jim Gettys' Blog - The chairman of the Fjord
Toke's Blog - Karlstad University's work on bloat
Voip Users Conference - Weekly Videoconference mostly about voip
Candelatech - A wifi testing company that "gets it".