A domain-ref must be THE official name of a registry, network, or host. It is a symbolic reference, within a name sub-domain. At times, it is necessary to bypass standard mechanisms for resolving such references, using more primitive information, such as a network host address rather than its associated host name.
To permit such references, this standard provides the domain-literal construct. Its contents must conform with the needs of the sub-domain in which it is interpreted.
Domain-literals which refer to domains within the ARPA Internet specify 32-bit Internet addresses, in four 8-bit fields noted in decimal, as described in Request for Comments #820, "Assigned Numbers." For example:
The names of "top-level" domains, and the names of domains under in the ARPA Internet, are registered with the Network Information Center, SRI International, Menlo Park, California.