[Cerowrt-devel] Fwd: qos in open commotion?
dave.taht at gmail.com
Sun May 25 15:56:18 EDT 2014
meant to cc cerowrt-devel on this...
---------- Forwarded message ----------
From: Dave Taht <dave.taht at gmail.com>
Date: Sun, May 25, 2014 at 12:55 PM
Subject: qos in open commotion?
To: andygunn at opentechinstitute.org, commotion-dev at lists.chambana.net
In response to your thread on qos in open commotion my list started a thread
You can and should run packet scheduling/aqm/qos in routers with 32MB
of memory or less. Some compromises are needed:
We strongly recomend that your edge gateways have aqm/packet
scheduling/qos on all their connections to the internet. See
innumerable posting on bufferbloat and the fixes for it...
Feel free to lift cerowrt's SQM scripts and gui from the ceropackages
repo for your own purposes. Openwrt barrier breaker qos-scripts are
pretty good too but don't work with ipv6 at the moment...
For the kind of results we get on cable:
Wifi has a built in QoS (802.11e) system but it doesn't work well in
and optimizing wireless-n aggregation works better.
As for fixing wifi, well, we know what to do, but never found any
funding for it. Ath9k is still horribly overbuffered and while
fq_codel takes some of the edge off of wifi (and recently we disabled
802.11e entirely in favor of fq_codel), and in cerowrt we reduce
aggregation to get better latency also - much more work remains to
truly make it scale down to levels of latency we consider reasonable
while (In other words, wifi latencies suck horribly now no matter
what yet we think we know how to improve that. Feel free to do
measurements of your mesh with tools like netperf-wrapper. There are
also a few papers out there now showing how bad wifi can get nowadays)
As for replacing pfifo_fast, openwrt barrier breaker replaced
pfifo_fast with fq_codel in barrier breaker a year ago.
fq_codel by default is essentially zero cost (64k per interface*hw
queues) and the default in openwrt on all interfaces by default now...
but the typical router cpus are so weak it is rare it kicks in except
at 100mbit and below. (where it can be wonderful) - and it's on a rate
limited (eg dsl or cable) system where it's most obviously useful.
Lastly, I've been running a deployed babel mesh network for 2 years
with fq_codel in it, 2 SSIDs per nanostation m5 and picostation, and
it runs pretty good. Recent tests on the ubnt edgerouter went well, as
Please give this stuff a shot. Your users will love it.
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