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An IP Address Extension Proposal (RFC1365)

IP.com Disclosure Number: IPCOM000002189D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 5 page(s) / 12K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Siyan: AUTHOR


This RFC suggests an extension to the IP protocol to solve the shortage of IP address problem, and requests discussion and suggestions for improvements.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 25% of the total text.

Network Working Group K. Siyan

Request for Comments: 1365 Siyan Consulting Services

September 1992

An IP Address Extension Proposal

Status of This Memo

This memo provides information for the Internet community. It does

not specify an Internet standard. Distribution of this memo is



This RFC suggests an extension to the IP protocol to solve the

shortage of IP address problem, and requests discussion and

suggestions for improvements.

1. Introduction and Background

The Internet community has a well-developed, mature set of protocols

that have been quite successful in providing network and transport

services to users. However, because of the spectacular success of the

TCP/IP protocols and the number of networks that desire connection to

the Internet, there is a shortage of network numbers that can be


The current network addressing scheme uses a 32-bit IP address that

has a network part and a local address part. The division between

the network part and the local address part has been defined in terms

of 5 address classes: class A, B, C, D, E. Of these, only class A,

B, C addresses are assigned to hosts. Class D is used for

multicasting and class E is reserved.

Class A has the highest order bit set to 0, a 7 bit network number

and a 24 bit host address.

Class B has the two higher order bits set to 10, a 14 bit network

number and a 16 bit host address.

Class C has the three higher order bit set to 110, a 21 bit network

number and a 8 bit host address.

Class D has the four higher order bits set to 1110.

Class E has four higher address bits set to 1111.

Increasing the size of the IP address field to more than 32 bits

would solve the problem, but at the expense of making a new IP header

definition that would be incompatible with the existing base of IP

implementations. OSI based solutions such as using CLNP have been

proposed but would take time to implement.

2. Proposal for IP extension

The IP header format should not be modified to minimize the changes

necessary for supporting the address extensions that are proposed in

this RFC. Instead an "escape" mechanism can be used to specify larger

address. The IP header length field is 4 bits and this allows a

maximum of fifteen 32-bit words where each word is 4 octets. The

minimum size of the IP header without options is 5 words, which

leaves 10 words for options. One can reserve 6 words (24 octets) for

the normal options and leave the remaining (4 words or 16 octets) for

a new option type that specifies an extended address. The details of

this mechanism are discussed below.

Class E should be defined with the its five high order bits set to

11110. Its current definition is that four 1's in the most

significant bits represent a class E address.

A new class F is pro...