RFC 2101 (rfc2101) - Page 1 of 13

IPv4 Address Behaviour Today

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Network Working Group                                       B. Carpenter
Request for Comments: 2101                                  J. Crowcroft
Category: Informational                                       Y. Rekhter
                                                                     IAB
                                                           February 1997


                      IPv4 Address Behaviour Today

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 main purpose of this note is to clarify the current
   interpretation of the 32-bit IP version 4 address space, whose
   significance has changed substantially since it was originally
   defined.  A short section on IPv6 addresses mentions the main points
   of similarity with, and difference from, IPv4.

Table of Contents

     1. Introduction.................................................1
     2. Terminology..................................................2
     3. Ideal properties.............................................3
     4. Overview of the current situation of IPv4 addresses..........4
       4.1. Addresses are no longer globally unique locators.........4
       4.2. Addresses are no longer all temporally unique............6
       4.3. Multicast and Anycast....................................7
       4.4. Summary..................................................8
     5. IPv6 Considerations..........................................8
     ANNEX: Current Practices for IPv4 Address Allocation & Routing..9
     Security Considerations........................................10
     Acknowledgements...............................................11
     References.....................................................11
     Authors' Addresses.............................................13

1. Introduction

   The main purpose of this note is to clarify the current
   interpretation of the 32-bit IP version 4 address space, whose
   significance has changed substantially since it was originally
   defined in 1981 [RFC 791].





Carpenter, et. al.           Informational
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