[Bloat] [aqm] the side effects of 330ms lag in the real world

[Toke Høiland-Jørgensen]

Jim Gettys <jg at freedesktop.org> writes:

> Now, if someone gives me real fiber to the home, with a real switch fabric
> upstream, rather than gpon life might be somewhat better (if the switches aren't
> themselves overbuffered.... But so far, it isn't.

As a data point for this, I have fibre to my apartment building and
ethernet into the apartment. I get .5 ms to my upstream gateway and
about 6 ms to Google. Still measured up to ~20 ms of bufferbloat while
running at 100 Mbps...

http://files.toke.dk/bufferbloat/data/karlstad/cdf_comparison.png

However, as that graph shows, it is quite possible to completely avoid
bufferbloat by deploying the right shaping. And in that case fibre
*does* have a significant latency advantage. The best latency I've seen
to the upstream gateway on DSL has been ~12 ms.

-Toke
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