Assigned numbers
RFC 820

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• rfc820

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

                            ASSIGNED NUMBERS

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

   ARPANET mail: POSTEL@ISIF

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

                        ASSIGNED 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 
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1 0|           NETWORK         |          Local Address        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             Class B Address

      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 1-0-0.  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 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             Class C Address

   One commonly used notation for internet host addresses divides the
   32-bit address into four 8-bit fields and specifies the value of each
   field as a decimal number with the fields separated by periods.  This
   is called the "dotted decimal" notation.  For example, the internet
   address of ISIF in dotted decimal is 010.002.000.052, or 10.2.0.52.

Postel                                                          [Page 2]



RFC 820                                                     January 1983