Name
Server (Listed only for zone-specific SOA). The name of the server
on which the zone resides.
Administrator
Email. The email address of the administrator responsible for the
master DNS name server.
Refresh
interval. The frequency (how often), in seconds, the slave name server
checks with the master name server for updated lookup information.
Retry
interval. The frequency (how long), in seconds, a slave server must
wait before retrying a failed zone transfer from the master name server.
Normally, the retry interval is shorter than the refresh interval.
Expire
interval. The upper limit, in seconds, that a slave name server can
use the lookup data it currently has before the data expires.
Minimum
Time To Live. The length of time, in seconds, the slave name server
can cache data.