[dns-operations] Strange Responses for 20.in-addr.arpa

[Peter Koch]

> ns1.csc.com and ns2.csc.com respond to queries for KEY, NXT and SIG RRs 
> but time out
> for DS, DNSKEY, NSEC, RRSIG and SSHFP RRs, so one guess is that there is a 
> middlebox
> of some description blocking queries for RR types that it doesn't know 
> about.

In addition, NS[12].CSC.COM aren't authoritative for 20.in-addr.arpa, but
for $N.20.in-addr.arpa with N = [0 .. 255].

-Peter