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The H Ratio for Address Assignment Efficiency (RFC1715)

IP.com Disclosure Number: IPCOM000003962D
Original Publication Date: 1994-Nov-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 3 page(s) / 7K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

C. Huitema: AUTHOR

Abstract

This document was submitted to the IETF IPng area in response to RFC 1550. Publication of this document does not imply acceptance by the IPng area of any ideas expressed within. Comments should be submitted to the author and/or the sipp@sunroof.eng.sun.com mailing list.

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 40% of the total text.

Network Working Group C. Huitema

Request for Comments: 1715 INRIA

Category: Informational November 1994

The H Ratio for Address Assignment Efficiency

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

This document was submitted to the IETF IPng area in response to RFC

1550. Publication of this document does not imply acceptance by the

IPng area of any ideas expressed within. Comments should be

submitted to the author and/or the sipp@sunroof.eng.sun.com mailing

list.

Table of Contents

1. Efficiency of address assignment . . . . . . . . . . . . . . 1

2. Estimating reasonable values for the ratio H . . . . . . . . 2

3. Evaluating proposed address plans. . . . . . . . . . . . . . 3

4. Security Considerations . . . . . . . . . . . . . . . . . . 4

5. Author's Address . . . . . . . . . . . . . . . . . . . . . . 4

1. Efficiency of address assignment

A substantial part of the "IPng" debate was devoted to the choice of

an address size. A recurring concept was that of "assignment

efficiency", which most people involved in the discussion expressed

as a the ratio of the effective number of systems in the network over

the theoretical maximum. For example, the 32 bits IP addressing plan

could in theory number over 7 billions of systems; as of today, we

have about 3.5 millions of addresses reported in the DNS, which would

translate in an efficiency of 0.05%.

But this classic evaluation is misleading, as it does not take into

account the number of hierarchical elements. IP addresses, for

example, have at least three degrees of hierarchy: network, subnet

and host. In order to remove these dependencies, I propose to use a

logarithmic scale for the efficiency ratio:

log (number of objects)

H = -----------------------

available bits

The ratio H is not too dependent of the number of hierarchical

levels. Suppose for example that we have the choice between two

levels, encoded on 8 bits each, and one single level, encoded in 16

bits. We will obtain the same efficiency if we allocate in average

100 elements at each 8 bits level, or simply 10000 elements in the

single 16 bits level.

Note that I use base 10 logs in what follows, because they are easier

to compute mentally. When it comes to large numbers, people ...