Did you discard probes that match *both* criteria, or just one of the criteria? In my preliminary experiments I did notice the very low RTT, but just filtering on unusual CHAOS replies seemed to be enough.
We only used chaos queries, since RTT suggests it but does not confirm it The thing is that the most roots are configured with IP anycast, so the same IP is shared among machines across the globe, meaning that the RTT varies depend on the relationship between the networks of the probe and the roots. What we did is not to run only for B-root, but for all letters (13 in total). That's what did, to double check.Reference 46 in the paper gives you measurement IDs for the other root letters.
I was running UDM towards a public resolver to perform CHAOS queries, but re-using the root measurements is quite clever, thanks for the idea!
Sure thing. The cool thing about these chaos measurements to the Roots is that they are "built-in" measurement. That means it uses *all* atlas probes, so you're covered. /giovane