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RFC 2136 defines four operations that are possible with dynamic DNS. They're
indicated using data provided with each operational entry. Note there are no
verbs or commands with dynamic DNS. The operations and their hint patterns are:
- Add a Resource Record. If a resource record needs to be inserted into a zone table, all the information for the new resource record must be provided in the update section entry. This includes data that identifies the target domain name, a resource record code, the resource record data, a network class code and a time-to-live value. If the resource record exists, the server will ignore the operation. If the domain name doesn't exist, it will be created with its only resource record consisting of the data provided in this entry. If the domain name exists but with some other data, the resource record data will be added to the existing entry.
- Delete a Specific Resource Record. If a specific resource record needs to be removed from the zone table, all the information that describes the resource record must be provided in the update section entry, with the exception of the time-to-live value and the network class code. To distinguish "add" operations from "delete" operations, a domain name that is to be deleted must have the network class code set to "none" (code value 254) as opposed to indicating a specific class. If the domain name does not exist in the zone table, the server will silently ignore the specific operation and return a response that indicates general success. If the resource record specified in the operation is the last resource record associated with the specified domain name, the entire domain name entry will be deleted from the zone table.
- Delete All Resource Records of a Specific Type. If all resource records of a specific type need to be removed from a specific domain name, (such as deleting all of the IPv4 Address resource records that are associated with a specific host), only the necessary information will be specified. This specific operation is identified by the update section entry containing a domain name, a resource record code (the group to be deleted), a network class code of "any" (code value 255), zero-length resource record data and a time-to-live value of 0. Note that the use of the "any" network class distinguishes this operation from the operation that deletes a specific resource record (the latter uses a network class of "none"). Also note that since all the matching resource records are to be deleted, no resource record data is provided.
- Delete All Resource Records. If a domain name needs to be entirely removed from the zone table, the update section must contain an entry which only describes that domain name. This specific operation is identified by the entry containing the domain name to be deleted, a resource record code of "all" (code value 255), a network class code of "any," zero-length resource record data, and a time-to-live value of 0.
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