[Babel-users] us vs ns resolution in babel rtt branch

[Dave Taht]

There have been many astounding improvements in latency in the linux stack
of late,
jesper (cc'd) has been doing tons of work in this area, another is in FIB
tables, and there are others
like low latency udp short circuits that I am not tracking well.

Jesper, what sort of numbers would you get along the lines' of baptiste's
benchmark
at 10GigE these days?

On Wed, Mar 18, 2015 at 6:28 AM, Baptiste Jonglez <
baptiste at bitsofnetworks.org> wrote:

> On Sun, Mar 15, 2015 at 03:00:12PM -0700, Dave Taht wrote:
> > I still kind of like getting down to ns resolution here. A single 64
> > byte packet at 10gigE takes like 64ns. I have discussed elsewhere my
> > hopes for using babel messages to determine the capacity and
> > utilization of a given network interface before, depending on
> > fq_codel's behavior as a substrate....
>
> I still believe other factors dwarf these 64 ns...
>
> I had done some measurements with the µs-precision code, on a direct
> gigabit link between two hosts (no switch):
>
>
> http://files.polyno.me/babel/evalperf/figures/32bits-rtt-ethernet-thinkbad-gilead.svg
>
> As you notice, ping6 reports 400 µs, babeld reports 800 µs, while the
> theoretical latency is 512 ns for a 64-bytes packet and 12 µs for a full
> 1500-bytes packet.  I am neglecting propagation delays (that would amount
> to about 50 ns for a 10-meter cable).
>
> So, the actual latency (measured either with ping or babel) is 3 orders of
> magnitude higher than the theoretical latency.  Do note that my tests were
> done with low-end hardware, so it might be better with high-performance
> NICs.
>
> Do you have latency measurements on 10G links?  If so, what tool do you
> use?  I believe both ping and babel are not very accurate at these
> timescales.
>
> Baptiste
>
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-- 
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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