RFC 3021 (rfc3021) - Page 1 of 10

Using 31-Bit Prefixes on IPv4 Point-to-Point Links

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Network Working Group                                          A. Retana
Request for Comments: 3021                                      R. White
Category: Standards Track                                  Cisco Systems
                                                               V. Fuller
                                                     GTE Internetworking
                                                            D. McPherson
                                                          Amber Networks
                                                           December 2000


           Using 31-Bit Prefixes on IPv4 Point-to-Point Links

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2000).  All Rights Reserved.

Abstract

   With ever-increasing pressure to conserve IP address space on the
   Internet, it makes sense to consider where relatively minor changes
   can be made to fielded practice to improve numbering efficiency.  One
   such change, proposed by this document, is to halve the amount of
   address space assigned to point-to-point links (common throughout the
   Internet infrastructure) by allowing the use of 31-bit subnet masks
   in a very limited way.

1. Introduction and Motivation

   The perceived problem of a lack of Internet addresses has driven a
   number of changes in address space usage and a number of different
   approaches to solving the problem:

   - More stringent address space allocation guidelines, enforced by the
     IANA and the regional address assignment authorities [RFC 2050].

   - Use of Network Address Translators (NATs), where a small number of
     IANA-compliant addresses are shared by a larger pool of private,
     non-globally routed addresses topologically behind a NAT box
     [RFC 1631].




Retana, et al.              Standards Track
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