Assigned numbers
RFC 790

Document Type RFC - Historic (September 1981; No errata)
Obsoleted by RFC 820
Obsoletes RFC 776
Last updated 2013-03-02
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Network Working Group                                          J. Postel
Request for Comments: 790                                            ISI
                                                          September 1981

Obsoletes RFCs:  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.  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

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
Protocol Handbook [17] prepared by the Network Information Center (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 790                                                   September 1981
                                                        Assigned Numbers
Network Numbers

                        ASSIGNED NETWORK NUMBERS

   This list of network numbers is used in the internet address [33].
   The Internet Protocol (IP) uses a 32 bit address 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, or class a, of address has a 7-bit network number
      and a 24-bit local address.  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, or class b, of address has a 14-bit network
      number and a 16-bit local address.  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, or class c, of address has a 21-bit network number
      and a 8-bit local address.  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 notation for internet host addresses commonly used 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.  For
   example, the internet address of ISIF is 010.020.000.052.

   This notation will be used in the listing of assigned network

Postel                                                          [Page 2]



RFC 790                                                   September 1981
                                                        Assigned Numbers
Network Numbers

   numbers.  The class a networks will have nnn.rrr.rrr.rrr, the class b
   networks will have nnn.nnn.rrr.rrr, and the class c networks will
   have nnn.nnn.nnn.rrr, where nnn represents part or all of a network
   number and rrr represents part or all of a local address or rest
   field.

   Assigned Network Numbers

   Class A Networks

      Internet Address  Name          Network                 References
      ----------------  ----          -------                 ----------
      000.rrr.rrr.rrr                 Reserved                     [JBP]
      001.rrr.rrr.rrr   BBN-PR        BBN Packet Radio Network    [DCA2]
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