On Tue, Apr 29, 2014 at 1:01 PM, Toke Høiland-Jørgensen <toke@toke.dk> wrote:

Jim Gettys <jg@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.

Media access is a killer on Cable too, putting the latency floor at around 8ms on my Docsis 3.0 Comcast service, though you can sometimes get lucky and piggyback. to somewhat lower latency, IIRC conversations with Greg White about how cable works.

- Jim

-Toke