RFC 1597 (rfc1597) - Page 2 of 8


Address Allocation for Private Internets



Alternative Format: Original Text Document



RFC 1597        Address Allocation for Private Internets      March 1994


   Hosts within enterprises that use IP can be partitioned into three
   categories:

      - hosts that do not require access to hosts in other enterprises
        or the Internet at large;

      - hosts that need access to a limited set of outside services
        (e.g., E-mail, FTP, netnews, remote login) which can be handled
        by application layer gateways;

      - hosts that need network layer access outside the enterprise
        (provided via IP connectivity);

      - hosts within the first category may use IP addresses that are
        unambiguous within an enterprise, but may be ambiguous between
        enterprises.

   For many hosts in the second category an unrestricted external access
   (provided via IP connectivity) may be unnecessary and even
   undesirable for privacy/security reasons.  Just like hosts within the
   first category, such hosts may use IP addresses that are unambiguous
   within an enterprise, but may be ambiguous between enterprises.

   Only hosts in the last category require IP addresses that are
   globally unambiguous.

   Many applications require connectivity only within one enterprise and
   do not even need external connectivity for the majority of internal
   hosts.  In larger enterprises it is often easy to identify a
   substantial number of hosts using TCP/IP that do not need network
   layer connectivity outside the enterprise.

   Some examples, where external connectivity might not be required,
   are:

      - A large airport which has its arrival/departure displays
        individually addressable via TCP/IP. It is very unlikely that
        these displays need to be directly accessible from other
         networks.

      - Large organisations like banks and retail chains are switching
        to TCP/IP for their internal communication.  Large numbers of
        local workstations like cash registers, money machines, and
        equipment at clerical positions rarely need to have such
        connectivity.






Rekhter, Moskowitz, Karrenberg & de Groot