RFC 3194 (rfc3194) - Page 1 of 7
The H-Density Ratio for Address Assignment Efficiency An Update on the H ratio
Alternative Format: Original Text Document
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