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.

8.  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.











 


RFC 819                                                     August 1982;


9.  Implementation

   The Actual Domains

      The initial set of top-level names include:

         ARPA

            This represents the set of organizations involved in the
            Internet system through the authority of the U.S. Defense
            Advanced Research Projects Agency.  This includes all the
            research and development hosts on the ARPANET and hosts on
            many other nets as well.  But note very carefully that the
            top-level domain "ARPA" does not map one-to-one with the
            ARPANET -- domains are administrative, not topological.

   Transition

      In the transition from the ARPANET naming convention to the
      Internet naming convention, a host name may be used as a simple
      name for an endpoint domain.  Thus, if "USC-ISIF" is an ARPANET
      host name, then "USC-ISIF.ARPA" is the name of an Internet domain.

10.  Summary

   A hierarchical naming convention based on the domain concept has been
   adopted by the Internet community.  It is an absolute naming
   convention defined along administrative rather than topological
   boundaries.  This naming convention is adaptive for interoperations
   with other naming conventions.  Thus, no standard convention needs to
   be imposed for interoperations among heterogeneous naming