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An IP Address Extension Proposal (RFC1365) Disclosure Number: IPCOM000002189D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2019-Feb-11
Document File: 6 page(s) / 7K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Siyan: AUTHOR

Related Documents

10.17487/RFC1365: DOI

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 27% 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 unlimited.


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 assigned.

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.

Siyan [Page 1]

RFC 1365 An IP Address Proposal September 1992

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 proposed with its six high order bits set to 111110. The new class F address would be placed in the same locations that are used for source and destination IP a...