[Cerowrt-devel] [aqm] ping loss "considered harmful"

Andrew Mcgregor andrewmcgr at google.com
Sun Mar 1 23:00:40 EST 2015

Hash all pings into one fq_codel bucket reserved for the purpose, so if
we're getting DoSed we drop them, otherwise if they stay thin they get

On 2 March 2015 at 14:57, Dave Taht <dave.taht at gmail.com> wrote:

> On this thread over here, an otherwise pretty clueful user chose
> openwrt's qos-scripts over the sqm-scripts, because sqm-scripts had
> *higher ping loss*.
> http://forums.dlink.com/index.php?topic=61634.msg251125#msg251125
> (I note that both fq_codel enabled QoS systems outperformed
> streamboost by a lot, which I am happy about)
> wow. It never registered to me that users might make a value judgement
> based on the amount of ping loss, and in looking back in time, I can
> think of multiple people that have said things based on their
> perception that losing pings was bad, and that sqm-scripts was "worse
> than something else because of it."
> sqm-scripts explicitly *deprioritizes* ping. In particular, this
> reduces the impact of ping floods from ipv6 to your entire /64, or to
> your whole ipv4, fairly well. And I had made the point that
> prioritizing ping was a bad idea here (including some dripping sarcasm
> later in the piece).
> http://www.bufferbloat.net/projects/cerowrt/wiki/Wondershaper_Must_Die
> but wow, it never occurred to me - in all these years - that ping was
> the next core metric on simple tests. I can be really dumb.
> I use netperf-wrapper and tend to ignore most of the ping data, but
> certainly on some benchmarks we have published ping doesn't look as
> good as the other stuff, *because it is deprioritized below all the
> other traffic*. Not strictly rate limited - as some systems do by
> default, including openwrt, which is impossible to get right - just
> deprioritized....
> How can we fix this user perception, short of re-prioritizing ping in
> sqm-scripts?
> --
> Dave Täht
> Let's make wifi fast, less jittery and reliable again!
> https://plus.google.com/u/0/107942175615993706558/posts/TVX3o84jjmb
> _______________________________________________
> aqm mailing list
> aqm at ietf.org
> https://www.ietf.org/mailman/listinfo/aqm

Andrew McGregor | SRE | andrewmcgr at google.com | +61 4 1071 2221
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