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