some notes regarding cerowrt

Dave Taht dave.taht at
Fri Jul 1 13:59:43 EDT 2011

I had hoped to have an alpha release of cerowrt 'Ocean City' out today.

Due to multiple conflicts on my schedule, and several packages that
have not landed (notably ahcp, netperf 2.5, iproute-2.6.39, debloat
with blacklists, and cerowrt-chrome) I'm slipping this to next friday
and taking off for the holiday.

A little history on this - cerowrt came from the wisp6 and iscwrt
projects and started more or less formally back in January, when I
realized the scope and extent of bufferbloat was a huge blocker to
future development of those, and indeed all - millions of - wireless-n
based network designs.

By May, cerowrt and iscwrt were looking pretty good and stable,
cerowrt had been through extensive QA, I had multiple happy (although
geeky) users in the field, good uptimes everywhere, and I was busy
working on getting iscwrt ready for world IPv6 day...

... and the projectbismark's 'get 15 routers to capetown for testing
in 3 weeks' thing came up.

It seemed a good idea to take cerowrt, add on the 3 (or so I thought)
extra packages, and get it out to more users for feedback. I thought I
could do that fast, and cheap, as I'd spent a week at georgia tech the
previous month training 3 people on how to do packaging and builds,
and thus thought coming in for the last two weeks of their effort
would be a win for everybody.

As it turned out, it was mostly successful, with only a few problems,
and with both cerowrt and bismark I fear we may end up with a success
disaster on our hands. It took a week longer than expected as fewer
resources were available, but still, getting a distro done in 4 weeks
is something that not a lot of people could pull off....

The problems we ran into with bismark in the final (extra) week forced
me to cancel iscwrt's release, and defer it for 3 months to a year,
which I deeply regret. After catching up on sleep, I have been folding
the 'baked' features from iscwrt back into cerowrt as a result. I
don't know if iscwrt will continue as a separate project at this


1) The most useful thing for me that happened from that exercise was
that the QoS scripts had a knee in them that cut raw bandwidth in the
third world by an unacceptable 30% at those lower bandwidths. I note
that this problem is not limited to openwrt, but probably exists
everywhere people are trying to do QoS, with the possible exception of

Getting to where the internet with or without QoS 'just works'
everywhere in the world - is a major goal.

2) Nobody non-geeky liked the xWrt gui. Additionally everyone found it
hard to adjust to using something other than as an

3) the need for wireless networking to 'just work' in cases where
someone is out of range of the main access point was repeatedly
re-proven, and the fact that nobody cared (until they hit the real
world) that I deliver that feature, bugged me, because I'd known

4) Bismark worked. The darn things seem to be staying up.  I care
mostly about that. Not only that but the previous generation of
cerowrt has routers that have now been up for several months. I'm even
happier about that. Many suggestions from both the bismark and cerowrt
efforts and results have made it into the openwrt mainline code,
multiple bugs found in the Linux kernel and tools have been fixed and
pushed out, and I'm utterly delighted about that and deeply grateful
to the openwrt and Linux and tool developers that have all been making
that happen.

So, to address some of the feedback we got from bismark in the cerowrt thing

1) QoS is still enabled by default in the gui, but the bandwidths are
set to 16Mbit down/4Mbit up, which is about the norm for most cable
systems in the US. I hope that with the additional traffic shapers
included, notably SFB, it will become possible to not have to be as
bandwidth aware as at present, but that will require more work and
research. Secondly, there is now the ability to simulate delays using
the netem emulator, which should have interesting results in the
ability to simulate other parts of the world as well as normal

2) The entire gui has been swapped from xWRt to luci. This cost me way
more time that I'd have liked, but the feedback from the pre-alpha
users is all good, and I cannot go back to xwrt.

The negative aspect is that I do not 'know' the language luci is
written in, 'lua', which makes it very difficult and slow for me to do
any actual work on the gui, at present.

3) Mesh networking is closer to 'just working'. Actually mesh
*routing* does 'just work', it's the address distribution scheme
(AHCP) that is busted. The problem has been found and multiple
approaches discussed as to how to fix it.

4) network numbering is such a pain that after discussing the problems
with the broken edge with jg, I pulled bind-latest (bind 9.8-P2) from
iscwrt into the cerowrt build. The user visible changes are that a
vendor provided name server is no longer needed (NXDOMAIN WORKS!),
that DNS 'just works' even without the internet, and you can get to
'gw.home.lan' by default rather than having to type a network address.
Under the hood, DNSsec is enable by default (at present) and seems to
'just work' and ipv6 autonumbering will usually result in a AAAA
address. It is also now possible (though not easy at present) to
finally rejoin your own network with that of your domain name, example
-, using bind9.


Update to kernel (from
iptables 1.4.11
netem, sfb, drr packet schedulers

wndr3700v2, x86 kvm, nano-m5 support now

some decent but still in progress vpn stuff
many other fixes...


I am deeply grateful to the openwrt people for their contributions
towards beating the bloat. Jow in particular, just extensively revised
and VASTLY improved the firewall code, and has contributed fixes to
the switch and network code that reduce the bloat and make routing
better, nbd continues to hammer at wireless-n,
and a cast of hundreds more continue to push the state of the art forward.

Deeply grateful also to nanog, the members of these lists, the linux,
netfilter, & networking folk, and project bismark for making all of
this happen.

I hope that cerowrt will help serve as a base for future
experimentation and network research  for many people. More
information about all these projects is available at

More news as it happens...

Have a good July 4!

Dave Täht
SKYPE: davetaht
US Tel: 1-239-829-5608

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