Using the Networking Test Tools in CeroWrt


The alttcp package makes it possible to change the default congestion control algorithm on the fly, as well as make other algorithms available to user programs.

The list of available algorithms is in /etc/config/alttcp
You can enable a change with /etc/init.d/alttcp start

It could use a gui.

Netperf (installed by default)

CeroWrt contains an advanced version of netperf which is capable of exercising socket prioritization, diffserv (tos) setting, and tcp congestion control algorithm selection. For the first time, these options can be set and controlled via remote control, thus making objective evaluations of the effect of these options in the real world, possible.

However using it on, to, or from a non-cerowrt device requires building it from svn sources at this time.


netperf -l 60 -Y AF31,EF -H t TCP_MAERTS - -K westwood,ledbat

The above runs a test for 60 seconds, using AF31 classification in one direction, EF in the other, talking to a router on, using a reverse stream (TCP_MAERTS is the reverse of TCP_STREAM, both are valid tests). The ‘–’ ends the options to the test in particular, and the -K controls what TCP algorithm is used on the local,remote sides.

Note: detecting bufferbloat generally requires running tests for considerably longer than netperf’s 10 second default.

Iperf (installed by default)

Rsync (installed by default)

CeroWrt contains a patched version of rsync that also supports Diffserv classification and user selectable tcp algorithms.

ShaperProbe (installed by default)

This tool is used to probe the available upstream bandwidth. It is still imperfect (inaccuracies of over 20% as to the real bandwidth available have been observed), and interacts badly with wireless hops, but seems useful for directly connected wired uplinks.






For more details, see Monitoring CeroWrt


For more details, see Monitoring CeroWrt

DitG (user installable)

We co-operate with this project, although their focus is on measuring the internet, and ours is on fixing it. As they use the same hardware as cerowrt, we plan to make available at least some of the Bismark Tools.

To edit this page, submit a pull request to the Github repository.
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Apr 12, 2024 Wiki page
What Can I Do About Bufferbloat?
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More about Bufferbloat
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Tests for Bufferbloat
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Getting SQM Running Right

Find us elsewhere

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


Comcast Research Innovation Fund
Nlnet Foundation
Shuttleworth Foundation

Bufferbloat Related Projects

OpenWrt Project
Congestion Control Blog
Flent Network Test Suite
The Cake shaper
CeroWrt (where it all started)

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".