[outages] usno.navy.mil disappeared?

[Stephane Bortzmeyer]

On Fri, Dec 21, 2018 at 02:48:03PM +0000,
 Steven Surdock via Outages <outages at outages.org> wrote 
 a message of 13 lines which said:

> Anyone know what is going on with The US Naval Observatory?
> Usno.navy.mil appears to be completely unresolvable.

Indeed, their four name servers do not reply to most packets.

Sometimes, it works:

% check-soa -i usno.navy.mil  
charon.usno.navy.mil.
	199.211.133.5: OK: 201709123 (180 ms)
metis.usnogps.navy.mil.
	Cannot get the IPv4 address: read udp 127.0.0.1:57410->127.0.0.1:53: i/o timeout
psyche.usno.navy.mil.
	192.5.41.214: OK: 201709123 (181 ms)
tycho.usnogps.navy.mil.
	Cannot get the IPv6 address: read udp 127.0.0.1:59763->127.0.0.1:53: i/o timeout

And sometimes not:

% check-soa -i usno.navy.mil 
charon.usno.navy.mil.
	199.211.133.5: ERROR: read udp 10.10.86.133:50346->199.211.133.5:53: i/o timeout
metis.usnogps.navy.mil.
	Cannot get the IPv4 address: read udp 127.0.0.1:51404->127.0.0.1:53: i/o timeout
psyche.usno.navy.mil.
	192.5.41.214: ERROR: read udp 10.10.86.133:34181->192.5.41.214:53: i/o timeout
tycho.usnogps.navy.mil.
	Cannot get the IPv6 address: read udp 127.0.0.1:50038->127.0.0.1:53: i/o timeout

RIPE Atlas probes see a majority of failures:

% blaeu-resolve -r 250 -q NS usno.navy.mil

[ERROR: NXDOMAIN] : 150 occurrences 
[ERROR: SERVFAIL] : 14 occurrences 
[charon.usno.navy.mil. metis.usnogps.navy.mil. psyche.usno.navy.mil. tycho.usnogps.navy.mil.] : 81 occurrences 
Test #18414784 done at 2018-12-21T14:58:04Z

May be a DoS? But I'm surprised by the number of NXDOMAIN
(unresponding servers should trigger SERVFAIL or timeout).