Re: [aqm] ping loss "considered harmful"

Andrew Mcgregor <andrewmcgr@google.com> Mon, 02 March 2015 10:49 UTC

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Date: Mon, 2 Mar 2015 21:49:22 +1100
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From: Andrew Mcgregor <andrewmcgr@google.com>
To: Dave Dolson <ddolson@sandvine.com>
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Cc: Jana Iyengar <jri@google.com>, "bloat@lists.bufferbloat.net" <bloat@lists.bufferbloat.net>, "dave.taht@gmail.com" <dave.taht@gmail.com>, "cerowrt-devel@lists.bufferbloat.net" <cerowrt-devel@lists.bufferbloat.net>, "aqm@ietf.org" <aqm@ietf.org>
Subject: Re: [aqm] ping loss "considered harmful"
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So, are you suggesting that, for example, Chrome's rather extensive network
debugging information get more publicised?  We can probably arrange that.

On 2 March 2015 at 21:47, Dave Dolson <ddolson@sandvine.com> wrote:

> I'm rather new to the aqm community, but IMHO, it is wrong to deprioritize
> the ping traffic by default. I would not have expected a forwarding agent
> to do this.
>
> And I think measuring ping times and loss is a reasonable thing to do,
> never expecting forwarding agents along the path to place more value on
> some IP packets than others. (Especially in my own network/lab when I did
> not configure such a policy)
>
> There aren't many tools available to an end user. Ping, traceroute, speed
> test... The network is a black box to most users.
>
> As for the flood attack aspect, of course a flood of pings should wait
> their turn in a queue and be dropped as the queue fills.
>
> It would be appropriate if this was fair to different ping flows in the
> same way TCP SYN packets are treated fairly. Treat ping flood like TCP SYN
> flood.
>
> My 2cents.
> -Dave Dolson
>
>
>
> ----- Original Message -----
> From: Dave Taht [mailto:dave.taht@gmail.com]
> Sent: Sunday, March 01, 2015 10:57 PM
> To: cerowrt-devel@lists.bufferbloat.net <
> cerowrt-devel@lists.bufferbloat.net>gt;; aqm@ietf.org <aqm@ietf.org>rg>; bloat <
> bloat@lists.bufferbloat.net>
> Subject: [aqm] ping loss "considered harmful"
>
> 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
>
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-- 
Andrew McGregor | SRE | andrewmcgr@google.com | +61 4 1071 2221