RFC2136 Dynamic Updates in the Domain Name System (DNS UPDATE)

The Domain Name System was originally designed to support queries of a statically configured database. While the data was expected to change, the frequency of those changes was expected to be fairly low, and all updates were made as external edits to a zone’s Master File. Using this specification of the UPDATE opcode, it is possible to add or delete RRs or RRsets from a specified zone. Prerequisites are specified separately from update operations, and can specify a dependency upon either the previous existence or nonexistence of an RRset, or the existence of a single RR. UPDATE is atomic, i.e., all prerequisites must be satisfied or else no update operations will take place. There are no data dependent error conditions defined after the prerequisites have been met