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Assigned numbers (RFC0820) Disclosure Number: IPCOM000003868D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2019-Feb-14
Document File: 22 page(s) / 27K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

J. Postel: AUTHOR

Related Documents

10.17487/RFC0820: DOI


This RFC is an old version, see RFC 870.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 7% of the total text.

Network Working Group J. Postel Request for Comments: 820 J. Vernon January 1983

Obsoletes RFCs: 790, 776, 770, 762, 758, 755, 750, 739, 604, 503, 433, 349 Obsoletes IENs: 127, 117, 93


This Network Working Group Request for Comments documents the currently assigned values from several series of numbers used in network protocol implementations. This RFC will be updated periodically, and in any case current information can be obtained from Jon Postel. The assignment of numbers is also handled by Jon, subject to the agreement between DARPA/IPTO and DDN/PMO about number allocation, documented in Appendix A of this RFC. If you are developing a protocol or application that will require the use of a link, socket, port, protocol, or network number please contact Jon to receive a number assignment.

Jon Postel USC - Information Sciences Institute 4676 Admiralty Way Marina del Rey, California 90291

phone: (213) 822-1511


The ARPANET community is making the transition form the ARPANET to the ARPA Internet. This has been characterized as the NCP/TCP transition [63], although many other the protocols are involved, too. The working documents for the new Internet environment have been collected by the Network Information Center (NIC) in a book entitled the "Internet Protocol Transition Workbook" [62].

Most of the protocols mentioned here are documented in the RFC series of notes. The more prominent and more generally used are documented in the "Internet Protocol Transition Workbook" or in the old "Protocol Handbook" [17] prepared by the NIC. Some of the items listed are undocumented.

In all cases the name and mailbox of the responsible individual is indicated. In the lists that follow, a bracketed entry, e.g., [17,iii], at the right hand margin of the page indicates a reference for the listed protocol, where the number cites the document and the "iii" cites the person.

Postel [Page 1]

RFC 820 January 1983 Assigned Numbers Network Numbers


The network numbers listed here are used as internet addresses by the Internet Protocol (IP) [33,62]. The IP uses a 32-bit address field and divides that address into a network part and a "rest" or local address part. The division takes 3 forms or classes.

The first type of address, or class A, has a 7-bit network number and a 24-bit local address. The highest-order bit is set to 0. This allows 128 class A 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| NETWORK | Local Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Class A Address

The second type of address, class B, has a 14-bit network number and a 16-bit local address. The two highest-order bits are set to 1-0. This allows 16,384 class B 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...