RFC1375 - Suggestion for New Classes of IP Addresses

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　　Network Working Group P. Robinson
Request for Comments: 1375 Tansin A. Darcos & Co.
October 1992

Suggestion for New Classes of IP Addresses

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 RFCsuggests a change in the method of specifying the IP address
to add new classes of networks to be called F, G, H, and K, to reduce
the amount of wasted address space, and to increase the available IP
address number space, especially for smaller organizations or classes
of connectors that do not need or do not want a full Class C IP
address.

Table of Contents

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Suggestion for new IP address classes . . . . . . . . . . . . . 2
Current Class C Address . . . . . . . . . . . . . . . . . . 3
Proposed new Class C Address . . . . . . . . . . . . . . . 4
Proposed "Class F" address . . . . . . . . . . . . . . . . 4
Proposed "Class G" address . . . . . . . . . . . . . . . . 4
Proposed "Class H" address . . . . . . . . . . . . . . . . 5
Proposed "Class K" address . . . . . . . . . . . . . . . . 5
Optional selection of routing codes by region . . . . . . . . . 5
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Security Considerations . . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7

Introduction

Currently, IP addresses on the Internet are 32-bit quantities which
are generally represented as four decimal numbers from 0 to 255,
separated by periods, sometimes called a "dotted" decimal number.
The current numbering scheme provides in general for three classes of
networks in general use (A,B, and C), and two other classes of
networks (D, E).

The Class A networks assign a large address space for the particular

network to allow up to 254^3 local machines [1]. The Class B network
assigns a somewhat smaller address space for the particular network
to allow up to 254^2 local machines. The Class C network assigns a
still smaller address space for the particular network to allow up to
254 local machines.

This memo proposes to assign part of the unused Class C address space
for smaller networks than are currently available. The term "Class
D" is used for the "multicast" capability and addresses in "Class E"
are reserved for future use. Therefore, these new features for which
capability is to be added is being referred to as classes F, G, H and
K.

Suggestion for new IP address classes

The most worrisome problem which appears in the literature is the
possibility of running out of address space for IP addresses. Various
schemes are being suggested such as subrouting, introduction of
additional bits, and other possibilities.

There is an even more serious matter. In all probability, I suspect
that eventually the Internet backbone will either become available to
anyone who wants to use it (like public highways) and the costs paid
for out of taxes or some other method which gets someone else to pay
for it, or eventually the Internet will be fully commercialized and
made available to anyone who wants to buy a permanent connection.
With the cost of hardware and connections dropping, some Computer
Bulletin Board Systems (BBSs) which are currently accessible via
telephone call may become accessible via TELNET or FTP. When a 9600
baud connection can be obtained for around the price of a phone line,
the demand for internet access will skyrocket. This almost certain
eventual availability to virtually anyone who wants a connection will
cause an even greater demand for internet addresses, which will
exacerbate this situation. One problem is in the granularity of IP
addressing, in that the smallest possible IP address one may obtain
allows for as high as 254 IP addresses. If someone wanted only to
put four or five computers on the Internet, more than 240 addresses
are wasted.

Many smaller installations would probably be interested either in
placing their computers and/or servers on the Internet (and perhaps
helping to pay the cost of running it) or in being able to access the
Internet directly, and perhaps making facilities on their machines
available to others; the problem being that IP addresses on Internet
are not readily available to small classes of users. Also, the
possibility exists of eventually placing non-computer and output-only
devices such as printers, facsimile machines, and visual pagers
directly on the Internet to allow people to send a message to a local

device simply by directing it to a specific internet site as an E-
Mail message.

The scheme proposed by this paper proposes to make a slight change in
one of the classes of network address in a manner which should not be
a significant problem for implementing, and should not cause a
significant hardship as the addresses to use for this purpose are not
now allocated anyway, and may draw some of the drain which would have
consumed Class C addresses in large quantity into quantities of Class
F, H, or K addresses which waste less IP address space.

This scheme I am proposing is to allow for very small networks (1 or
2, 1-7, or 1-15, depending on the number of addresses the
administrator of that site thinks he will need), by reconstructing
the network address to include what is nominally part of the local
address. If bridges and routers (and other hardware and software) do
not assume that only the last 8 bits make up a local address and
permit smaller spaces for local addresses, then this method should
not cause problems. Sites needing less than a close order of 256 IP
addresses could simply apply for 2 or more contiguous blocks of Class
F numbers.

Currently, a Class C address consists of a 32-bit number in which the
leftmost 3 bits consist of "110" [2]:

The third type of address, class C, has a 21-bit network number
and a 8-bit local address. The three highest-order bits are set
to 1-1-0. This allows 2,097,152 class C networks.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 0| NETWORK | Local Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Current Class C Address

This memo proposes to change Class C addresses to be 4-bit numbers
beginning with "1100":

The third type of address, class C, has a 20-bit network number and a
8-bit local address. The four highest-order bits are set to 1-1-0-0,
This allows 1,048,576 class C networks.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 0 0| NETWORK | Local Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Proposed new Class C Address

This memo then proposes to add four new types of addresses, to be
referred to as "Class F", "Class G", "Class H", and "Class K" [3].
These would all use part of the "old" class C address by all using IP
addresses that begin with the 4-bit sequence "1101". The Class F
addresses would begin with the binary code sequence "11010", Class G
addresses begin with "110110", Class H addresses with "1101110", and
Class K with "1101111".

Class F addresses will be used for networks having from 1-15 sites
[4], where the number could be expected to exceed 7. Class F
addresses are defined as follows:

The sixth type of address, class F, has a 23-bit network number, and
a 4-bit local address. The five highest-order bits are set to 1-1-
0-1-0. This allows 16,777,256 class F networks.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | Local |
|1 1 0 1 0| NETWORK |Address|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Proposed "Class F" address

Class G is to be defined as follows:

The seventh type of address, class G, is reserved for future
use. The six highest-order bits are set to 1-1-0-1-1-0.

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
|1 1 0 1 1 0| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Proposed "Class G" address

Class H is for small networks which are not expected to exceed 7

connected IP addresses. Class H is to be defined as follows:

The eighth type of address, class H, has a 22-bit network
number, and a 3-bit local address. The seven highest-order bits
are set to 1-1-0-1-1-1-0. This allows 4,194,304 Class H
addresses [5].

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |Local|
|1 1 0 1 1 1 0| NETWORK | Addr|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Proposed "Class H" address

Class K is for sites which either will only have one or two connected
addresses [6]. Class K is to be defined as follows:

The eighth type of address, class K, has a 25-bit network
number, and a 1-bit local address. The seven highest-order bits
are set to 1-1-0-1-1-1-1. This allows 33,554,432 Class K
addresses [7].

1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |*|
|1 1 0 1 0 0| NETWORK | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

* = Local Address, 1 or 0
Proposed "Class K" address

Optional selection of routing codes by region

Because of the possibility of confusion, some method similar to the
international dialing plan might be set up, in which bits 5-8 in
Class F, bits 7-10 in Class H, and bits 6-9 in Class K could be used
to define what part of the world the particular address is in, in a
manner similar to the international telephone dialing system, which
uses the first digit of the international telephone number to
determine the region being used. The current method for assigning
international dialing codes is:

1 North America 6 Oceania, Australia
2 Africa 7 Ex-Soviet Union Countries
3 Europe 8 Asia
4 Europe 9 Mideast
5 South America and Mexico

If a similar method is used, I would recommend assigning 0,1,10 and
11 to North America, 8 and 12 to Asia, and leaving 13 through 15 for
other areas as needed. Note that this would simply make some routing
choices easier, it is not precisely necessary that this be done,
since currently routing is generally done using the shortest path to
a site and IP numbers don't really relate to any specific address
anywhere in the world.

The number form of a class F, G, H or K address could still be listed
in the standard form n.n.n.n, as long as it is not assumed that the
4th chunk number alone identifies a local address and that numbers
with the same preceding 3 chunks do not necessarily belong to the
same network.

Summary

In order to make the address space available, even if the method to
implement this feature is not presently available, it is suggested
that Class F, G, H, and K address space should be taken out of Class
C space and reserved for the purpose of allowing smaller-sized
networks so that this feature may be made available. Since Class C
addresses currently are only using the equivalent of one Class A
number anyway, this should not cause a problem.

Notes

[1] Common practice dictates that neither an address 0 nor 255 should
be used in any "dotted" address.

[2] Reynolds, J., and J. Postel, "Assigned Numbers", STD 2, RFC1340,
USC/Information Sciences Institute, July 1992.

[3] To prevent confusion, no class "I" or "J" address was created by
this memo.

[4] It is expected that if the higher part of the network address
occupying the 4-bits to the left of the Class F address are
neither 0 nor 15, that a class F site could have 16 machines. If
the 4-bits to the left are all 0, the Class F site must not use
number 0. If the four bits are all 1, the site must not use
number 15.

[5] It may be that Class H numbers are more appropriate for classes
of addresses that will not have as high a demand for access via
Internet addresses such as facsimile machines and pagers. (The
end digit could be used to determine class of service, i.e., 0
for tone only, 1 and 2 for numeric only, 3 4 and 5 for
alphanumeric, and 6 and 7 for facsimile machines. Or some
combination of these according to the demand. Remember,
Internet won't always be just text messages and file transfers;
we may eventually see things like voice telephone calls or voice
data being placed to an Internet address just like calls made
via the telephone system. This would require a whole change in
the way things are done, but it's always best to look at the
future.

[6] It is suggested that addresses in this range not be assigned
where the 7 bits to the left of the local number are all the
same (all 0 or all 1), to allow all Class K addresses to have
two local addresses.

[7] Different things can be done with different capabilities. One
thought was to set up some group of numbers and use them to
indicate systems which are "gateway" systems, i.e., the top set
of numbers in Class K could indicate that subnets are required
after those numbers, similar to the use of an extension number on
the switchboard of a large organization. Another possibility is
to assign some of the numbers to specific classes of devices,
such as number-only pagers and electronic display devices.

Security Considerations

Security issues are not discussed in this memo.

Author's Address

Paul Robinson
Tansin A. Darcos & Company
8604 Second Avenue #104
Silver Spring, MD 20910 USA

Phone: 202-310-1011
Telex: 6505066432MCI UW
E-mail: TDARCOS@MCIMAIL.COM

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