Some ideas from a mailing list:
quick and dirty:jens@screen:~$ dig nanog.org @8.8.8.8 | grep "Query time" ;; Query time: 16 msec jens@screen:~$ dig nanog.org @1.1.1.1 | grep "Query time" ;; Query time: 3 msecIndeed. For instance, the delay depends wether the cache it hot or cold (measuring response time for an authoritative server is easier).
also could use ripe atlas ...
Which embeds clients for ICMP Echo, DNS, NTP, TLS, arbitrary TCP (with some hacks), and, with serious limitations, HTTP.
use dig -u to get microsecond resolution, e.g.$ dig -u @131.111.8.42 nanog.org | grep time: ;; Query time: 611 usec
I recommend that eyeball networks don't run any external recursive server for optimal CDN performance. Yes, some CDNs support other methods, but not all. If not all do, then the requirement remains. See On Firefox Moving DNS to a Third Party