A zone is stored in a
map[string]map[int]*ZRRset
where string is the qname and int (in the second map) is
qclass * <large number> + qtype, thereby making it unique.
ZRRset holds:
RRs RRset
RRsigs RRset
Nsec RR
Nsec3 RR
Glue bool
Which holds the RRset for the zone contents. This is grouped
together for DNSSEC purposes, but also helps in non-DNSSEC zones.
(There is of course a increase in memory usage).
Miek Gieben