Implications of Various Address Allocation Policies for Internet Routing
RFC 2008

Document Type RFC - Best Current Practice (October 1996; No errata)
Also known as BCP 7
Last updated 2013-03-02
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Network Working Group                                      Y. Rekhter
Request for Comments: 2008                                      T. Li
BCP: 7                                                  Cisco Systems
Category: Best Current Practice                          October 1996

              Implications of Various Address Allocation
                     Policies for Internet Routing

Status of this Memo

   This document specifies an Internet Best Current Practices for the
   Internet Community, and requests discussion and suggestions for
   improvements.  Distribution of this memo is unlimited.

IESG Note:

   The addressing constraints described in this document are largely the
   result of the interaction of existing router technology, address
   assignment, and architectural history.  After extensive review and
   discussion, the authors of this document, the IETF working group that
   reviewed it, and the IESG have concluded that there are no other
   currently deployable technologies available to overcome these
   limitations.  In the event that routing or router technology develops
   to the point that adequate routing aggregation can be achieved by
   other means or that routers can deal with larger routing and more
   dynamic tables, it may be appropriate to review these constraints.

1 Abstract

   IP unicast address allocation and management are essential
   operational functions for the Public Internet. The exact policies for
   IP unicast address allocation and management continue to be the
   subject of many discussions. Such discussions cannot be pursued in a
   vacuum - the participants must understand the technical issues and
   implications associated with various address allocation and
   management policies.

   The purpose of this document is to articulate certain relevant
   fundamental technical issues that must be considered in formulating
   unicast address allocation and management policies for the Public
   Internet, and to provide recommendations with respect to these

   The major focus of this document is on two possible policies,
   "address ownership" and "address lending," and the technical
   implications of these policies for the Public Internet.  For the
   organizations that could provide reachability to a sufficiently large

Rekhter & Li             Best Current Practice                  [Page 1]
RFC 2008                                                    October 1996

   fraction of the total destinations in the Internet, and could express
   such reachability through a single IP address prefix the document
   suggests to use the "address ownership" policy. However, applying the
   "address ownership" policy to every individual site or organization
   that connects to the Internet results in a non-scalable routing.

   Consequently, this document also recomments that the "address
   lending" policy should be formally added to the set of address
   allocation policies in the Public Internet. The document also
   recommends that organizations that do not provide a sufficient degree
   of routing information aggregation, but wish to obtain access to the
   Internet routing services should be strongly encouraged to use this
   policy to gain access to the services.

2 On the intrinsic value of IP addresses

   Syntactically, the set of IPv4 unicast addresses is the (finite) set
   of integers in the range 0x00000000 - 0xDFFFFFFF. IP addresses are
   used for Network Layer (IP) routing. An IP address is the sole piece
   of information about the node injected into the routing system.

   The notable semantics of an IP unicast address is its ability to
   interact with the Public Internet routing service and thereby
   exchange data with the remainder of the Internet. In other words, for
   the Public Internet, it is the reachability of an IP address that
   gives it an intrinsic value. Observe, however, that IP addresses are
   used outside of the Public Internet. This document does not cover the
   value of addresses in other than the Public Internet context.

   The above implies that in the Public Internet it is the service
   environment (the Internet) and its continued operation, including its
   routing system, which gives an IP address its intrinsic value, rather
   than the inverse. Consequently, if the Public Internet routing system
   ceases to be operational, the service disappears, and the addresses
   cease to have any functional value in the Internet. At this point,
   for the Public Internet, all address allocation and management
   policies, including existing policies, are rendered meaningless.

3 Hierarchical routing and its implication on address allocation

   Hierarchical routing [Kleinrock 77] is a mechanism that improves the
   scaling properties of a routing system. It is the only proven
   mechanism for scaling routing to the current size of the Internet.

   Hierarchical routing requires that addresses be assigned to reflect
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