The Zone Section has the same format as that specified in [RFC1035 4.1.2], with the fields redefined as follows:
1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| |
/ ZNAME /
/ /
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ZTYPE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ZCLASS |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
UPDATE uses this section to denote the zone of the records being updated. All records to be updated must be in the same zone, and therefore the Zone Section is allowed to contain exactly one record. The ZNAME is the zone name, the ZTYPE must be SOA, and the ZCLASS is the zone's class.