RFC 1335 (rfc1335) - Page 1 of 7
A Two-Tier Address Structure for the Internet: A Solution to the Problem of Address Space Exhaustion
Alternative Format: Original Text Document
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