RFC 3194 (rfc3194) - Page 1 of 7

The H-Density Ratio for Address Assignment Efficiency An Update on the H ratio

Network Working Group                                          A. Durand
Request for Comments: 3194                              SUN Microsystems
Updates: 1715                                                 C. Huitema
Category: Informational                                        Microsoft
                                                           November 2001


       The Host-Density Ratio for Address Assignment Efficiency:
                        An update on the H ratio

Status of this Memo

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

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   This document provides an update on the "H ratio" defined in RFC
   1715.  It defines a new ratio which the authors claim is easier to
   understand.

1. Evaluating the efficiency of address allocation

   A naive observer might assume that the number of addressable objects
   in an addressing plan is a linear function of the size of the
   address.  If this were true, a telephone numbering plan based on 10
   digits would be able to number 10 billion telephones, and the IPv4 32
   bit addresses would be adequate for numbering 4 billion computers
   (using the American English definition of a billion, i.e. one
   thousand millions.) We all know that this is not correct: the 10
   digit plan is stressed today, and it handles only a few hundred
   million telephones in North America; the Internet registries have
   started to implement increasingly restrictive allocation policies
   when there were only a few tens of million computers on the Internet.

   Addressing plans are typically organized as a hierarchy: in
   telephony, the first digits will designate a region, the next digits
   will designate an exchange, and the last digits will designate a
   subscriber within this exchange; in computer networks, the most
   significant bits will designate an address range allocated to a
   network provider, the next bits will designate the network of an
   organization served by that provider, and then the subnet to which
   the individual computers are connected.  At each level of the



Durand & Huitema             Informational