Network Working Group E. Gerich
Request for Comments: 1814 Merit Network Inc.
Category: Informational June 1995

Unique Addresses are Good

Status of this Memo

This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.

Abstract

The IAB suggests that while RFC1597 establishes reserved IP address
space for the use of private networks which are isolated and will
remain isolated from the Internet, any enterprise which anticipates
external connectivity to the Internet should apply for a globally
unique address from an Internet registry or service provider.

IntrodUCtion

With the advent of RFC1466 and RFC1597 the criteria for the
allocation of unique IP numbers and the reservation of unique IP
numbers have been defined. The IAB and the IANA wish to offer
guidance to the Internet registries as to the application of these
two documents. The author submits this document as an informational
RFCon behalf of the Internet Architecture Board and the IANA.

Guidance to Internet Registries

RFC1466 lists the criteria to which Internet registries should
conform. One of the criteria is that the Internet registry is
committed to allocate IP numbers according to the guidelines
established by the IANA and the IR. Those guidelines (for Classes A,
B, and C addresses) are documented in RFC1466.

Internet Registries have agreed to comply with the guidelines
established by RFC1466 and therefore, if an organization meets the
size requirement for the requested address(es) and submits an
engineering plan, the organization has fulfilled the necessary
requirements. The Internet Registry will make the allocation based
on the established criteria.

The preconditions defined in RFC1466 are limited to number of hosts
and subnets as well as an engineering plan. The existence of private
address space (RFC1597) shall not prevent an enterprise from
oBTaining public address space according to the allocation criteria
(currently, RFC1466).

An enterprise may be required by a Internet registry to submit an
engineering plan documenting a realistic deployment schedule and
reasonable attention to conservation of address space to support the
size of the enterprise's request for globally unique IP addresses.

It is perfectly appropriate for an Internet registry to inform an
organization of the provisions of RFC1597. Any organization
considering the use of private network numbers should carefully
consider the potential advantages and possible problems as discussed
in RFCs 1597 and 1627.

RFC1597 establishes reserved IP address space for the use of private
networks which are isolated and will remain isolated from the
Internet. Thus RFC1597 documents a way that private enterprises may
assure that their networks will remain segregated from the Internet.
The addresses designated in RFC1597 should not be routed by the
Internet.

Any enterprise with a significantly large number of hosts which might
require external connectivity to the Internet at the IP layer should
apply for a block of globally unique addresses from an Internet
registry. Enterprises with a small to medium number of hosts that
require external connectivity to the Internet at the IP layer should
eXPect to use globally unique addresses for these hosts, assigned to
them by their current Internet service provider from its own assigned
addresses, if it has such addresses to distribute.

If an enterprise with a small to medium number of hosts desires
unique IP addresses, and is unable to obtain them under reasonable
conditions from a service provider, or has no service provider, the
Internet registries are recommended to assign such addresses without
conditions with respect to service provider selection. The
registries should make clear to the enterprise that when the
enterprise decides to connect to the Internet, the assigned addresses
are no guarantee of Internet-wide IP connectivity. In fact, some
service providers may require renumbering as a condition of
connectivity.

Any organization which anticipates having external connectivity is
encouraged to apply for a globally unique IP address. Globally
unique addresses are necessary to differentiate between destinations
on the Internet. One must understand, however, that the globally

unique address by itself does not necessarily guarantee global
connectivity. Individual network service providers may place
restrictions on what addresses they will or will not route based on
operational limitations.

References

[1] Gerich, E., "Guidelines for Management of IP Address Space", RFC
1466, Merit Network Inc., May 1993.

[2] Rekhter, Y., Moskowitz, B., Karrenberg, D., and G. de Groot,
"Address Allocation for Private Internets", RFC1597, T.J. Watson
Research Center, IBM Corp., Chrysler Corp., RIPE NCC, RIPE NCC,
March 1994.

Security Considerations

Security issues are not discussed in this memo.

Author's Address

Elise Gerich
Merit Network Inc.
4251 Plymouth Road
Ann Arbor, MI 48105

Phone: +1 313 764 9430
Fax: +1 313 747 3745