mal DNS operation,
this kind of response is required in order to find names beneath a
delegation... DNS
operation, this kind of response is not required for resolution or
for correctly answering a... TTL of every
resource record in an RRset is required to be the same ([RFC2181],
Section 5.2).
... on of [RFC6840],
NSEC records are no longer required for signed zones: a signed
zone might inclu