RFC 1335 (rfc1335) - Page 1 of 7

A Two-Tier Address Structure for the Internet: A Solution to the Problem of Address Space Exhaustion

Network Working Group                                          Z. Wang
Request for Comments: 1335                                J. Crowcroft
                                             University College London
                                                              May 1992


             A Two-Tier Address Structure for the Internet:
         A Solution to the Problem of Address Space Exhaustion

Status of this Memo

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

Abstract

   This RFC presents a solution to problem of address space exhaustion
   in the Internet.  It proposes a two-tier address structure for the
   Internet.  This is an "idea" paper and discussion is strongly
   encouraged.

Introduction

   Address space exhaustion is one of the most serious and immediate
   problems that the Internet faces today [1,2].  The current Internet
   address space is 32-bit.  Each Internet address is divided into two
   parts: a network portion and a host portion.  This division
   corresponds the three primary Internet address classes: Class A,
   Class B and Class C.  Table 1 lists the network number statistics as
   of April 1992.

                      Total       Allocated     Allocated (%)
   Class A              126            48            54%
   Class B            16383          7006            43%
   Class C          2097151         40724             2%

          Table 1: Network Number Statistics (April 1992)

   If recent trends of exponential growth continue, the network numbers
   in Class B will soon run out [1,2].  There are over 2 million Class C
   network numbers and only 2% have been allocated.  However, a Class C
   network number can only accommodate 254 host numbers which is too
   small for most networks.  With the rapid expansion of the Internet
   and drastic increase in personal computers, the time when the 32-bit
   address space is exhausted altogether is also not too distant [1-3].

   Recently several proposals have been put forward to deal with the



Wang & Crowcroft