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Dave Täht, 03/19/2012 05:57 pm

Overview of the CeroWrt Project

Bufferbloat is a huge drag on Internet performance created, ironically, by previous attempts to make it work better. Eric Raymond wrote this one-sentence summary of the problem: "Bloated buffers lead to network-crippling latency spikes." You can read more about this problem at the main Bufferbloat site.

CeroWrt is a project built upon the OpenWrt firmware to resolve these endemic problems in home networking today, and to push the state of the art of edge networks and routers forward. Projects include proper IPv6 support, tighter integration with DNSSEC, and most importantly, reducing bufferbloat in both the wired and wireless components of the stack.


Our plan is to produce a stable build that can be used as both a production router, and as a platform for further research into algorithms for solving state of the art problems in networking. The CeroWrt 3.3 series of builds include the following features and capabilities:

  • Linux 3.3 kernel. Many of the fixes for bufferbloat are being implemented in this 3.3 kernel, so we are tracking these developments carefully. http://kernel.org
  • Active Queue Management fixes for bufferbloat including: Byte Queue Limits (BQL - already incorporated into the 3.3 kernel), Stochastic Fair Queueing-Random Early Drop (SFQRED), working ECN, and other queue disciplines http://bufferbloat.net
  • IPv6 support. Another major goal of CeroWrt is to make IPv6 networking in the home as simple as IPv4.
  • Babel mesh routing protocol (1.3.1-2 release).
  • DNSSEC and DNSSEC proxying - Secure extensions to the DNS system. Proxying is currently in testing.
  • OpenWrt features. Because we track the OpenWrt code base carefully, we incorporate most of the capabilities of that distribution. We actively push our changes/enhancements back toward the OpenWrt trunk. http://openwrt.org
  • An attractive web GUI for configuration - LuCI

Our plan is to produce a stable build that can be used as both a production router, and as a platform for further research into algorithms for solving state of the art problems in networking.


The current CeroWrt 3.3 is build 3.3-rc7-5, built on 16 March 2012. Read the CeroWrt 3.3 Release Notes or the News Page for details.

Sources of Information about the project

Glossary for Bufferbloat Topics: Glossary
General Bufferbloat list: https://lists.bufferbloat.net/listinfo/bloat
CeroWrt-devel list: https://lists.bufferbloat.net/listinfo/cerowrt-devel
CeroWrt-Commits list: https://lists.bufferbloat.net/pipermail/cerowrt-commits/
Lab Notebook in Github: https://github.com/dtaht/deBloat
IRC: Find us on IRC on chat.freenode.net, #bufferbloat channel

Try the Software

The current Linux 3.3 builds are usable, although they may have bugs. They give considerable improvement to the bufferbloat problem and continue to provide a good platform for testing various algorithms.

Many people are using these builds as a second router in their homes. A few brave souls are using it as their production router.

Download CeroWrt 3.3 builds: http://huchra.bufferbloat.net/~cero1/3.3/

Hardware Requirements

To minimize the effects of hardware dependencies, we have chosen the Netgear WNDR3700v2 or WNDR3800 as the sole hardware for the experiments. The open source support for it is extensive, it has a capable processor with 16MB of flash and 64MB of RAM, it supports a USB flash stick, they are inexpensive (around $120-130). The WNDR3800 has more RAM (128MB instead of 64), but either of these models will be fine for these experiments. The WNDR3700v3 model that has recently appeared on the market does not work with CeroWrt; purchase the WNDR3800 if you want to be future-proof.


The documents below are correct for the current Linux 3.3 builds.

Older Information

The Historical Documents page links to many documents that describe the history of the project.

flanders320fade.jpg (18.4 kB) Rich Brown, 01/22/2012 12:14 pm