On Thu, Jan 16, 2020 at 04:33:47PM +0100,
 Klaus Darilion <klaus.mailinglists@pernau.at> wrote
 a message of 48 lines which said:

> - analyze the probe locations (ie. country, continent)

Instead of analyzing it afterwards, why not directly asking probes on
the place you're interested in?

I often use NSID to watch anycast servers, indeed:

% blaeu-resolve --requested 100 --area West --nameserver $(dig +short +nodnssec d.nic.fr A) --type SOA --nsid --displayrtt fr
Nameserver 194.0.9.1
[NSID: b'dns.th2.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 34 occurrences Average RTT 146 ms
[NSID: b'dns.fra.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 3 occurrences Average RTT 100 ms
[NSID: b'dns.nyc.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 35 occurrences Average RTT 56 ms
[NSID: b'dns.ix1.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 4 occurrences Average RTT 116 ms
[TIMEOUT] : 2 occurrences Average RTT 0 ms
[NSID: b'dns.mrs.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 10 occurrences Average RTT 156 ms
[NSID: b'dns.ams.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 8 occurrences Average RTT 101 ms
[NSID: b'dns.lon.nic.fr' nsmaster.nic.fr. hostmaster.nic.fr. 2225269298 3600 1800 3600000 5400] : 2 occurrences Average RTT 154 ms
[nsmaster.nic.fr. hostmaster.nic.fr. 2225269297 3600 1800 3600000 5400] : 1 occurrences Average RTT 24 ms
Test #23843409 done at 2020-01-16T15:43:10Z

Note the wonders of BGP: only a minority of probes use the instance in
New York City (the fastest one) :-(

Note also that the last result comes from a transparent proxy,
redirecting to a cache.