Associated with each domain there must be a naming authority to assign simple names and ensure proper distinction among simple names. Note that if the use of partially qualified names is allowed in a sub-domain, the uniqueness of simple names inside that sub-domain is insufficient to avoid ambiguity with names outside the subdomain. Appendix B discusses simple name assignment in a sub-domain that would allow the use of partially qualified names without ambiguity. Administratively, associated with each domain there is a single person (or office) called the registrar. The registrar of the naming universe specifies the top-level set of domains and designates a registrar for each of these domains. The registrar for any given domain maintains the naming authority for that domain. For user applications such as file transfer and terminal access, the remote host needs to be named. To be compatible with ARPANET naming convention, a host can be treated as an endpoint domain. Many operating systems or programming language run-time environments provide functions or calls (JSYSs, SVCs, UUOs, SYSs, etc.) for standard services (e.g., time-of-day, account-of-logged-in-user, convert-number-to-string). It is likely to be very helpful if such a RFC 819 August 1982; function or call is developed for translating a host name to an address. Indeed, several systems on the ARPANET already have such facilities for translating an ARPANET host name into an ARPANET address based on internal tables. We recommend that this provision of a standard function or call for translating names to addresses be extended to accept names of Internet convention. This will promote a consistent interface to the users of programs involving internetwork activities. The standard facility for translating Internet names to Internet addresses should include all the mechanisms available on the host, such as checking a local table or cache of recently checked names, or consulting a name server via the Internet.

Mail Relaying: Relaying is a feature adopted by more and more mail systems. Relaying facilitates, among other things, interoperations between heterogeneous mail systems. The term "relay" is used to describe the situation where a message is routed via one or more intermediate points between the sender and the recipient. The mail relays are normally specified explicitly as relay points in the instructions for message delivery. Usually, each of the intermediate relays assume responsibility for the relayed message [3]. A point should be made on the basic difference between mail relaying and the uucp naming system. The difference is that although mail relaying with absolute naming can also be considered as a form of source routing, the names of each intermediate points and that of the destination are universally interpretable, while the host names along a source route of the uucp convention is relative and thus only locally interpretable. The Internet naming convention explicitly allows interoperations among heterogeneous systems. This implies that the originator of a communication may name a destination which resides in a foreign system. The probability is that the destination network address may not be comprehensible to the transport system of the originator. Thus, an implicit relaying mechanism is called for at the boundary between the domains. The function of this implicit relay is the same as the explicit relay.