[atlas] probe resolution, overhead, or ...?

> As far as I know, a dedicated (x86) box that just acts as a ping
> target is best for round trip latency measurements.

that is what we are doing, though a collection of targets across a
topology.  though using the data plane to measure the control plane,
one of our often played songs.  so changes in rtt are critical.

but, like good little nerds, we are trying to calibrate the meters
before we use them in a real experiment.  

don't get me wrong.  for something the size of my thumb, the atlas
probes are cute.  and we hope they will be useful.  but knowing the
limits and accuracy of one's tools is a critical part of good research.

randy