An Rdata is typed data in one of the known DNS datatypes, for example
A, the IPv4 address of a host, or type
MX, how to route
mail. Unlike the DNS RFC concept of RR, an Rdata is not bound to
an owner name. Rdata is immutable.
Rdata of the same type can be grouped into an unnamed set, an Rdataset, or into a named set, an RRset.