rfc990.txt

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Network Working Group                                        J. Reynolds
Request for Comments:  990                                     J. Postel
                                                                     ISI
Obsoletes RFCs:  960, 943, 923, 900,                       November 1986
870, 820, 790, 776, 770, 762, 758,
755, 750, 739, 604, 503, 433, 349
Obsoletes IENs:  127, 117, 93


                            ASSIGNED NUMBERS


Status of this Memo

   This memo is an official status report on the numbers used in
   protocols in the ARPA-Internet community.  Distribution of this memo
   is unlimited.

Introduction

   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 Joyce Reynolds.  The assignment of numbers is also handled by
   Joyce.  If you are developing a protocol or application that will
   require the use of a link, socket, port, protocol, network number,
   etc., please contact Joyce to receive a number assignment.

      Joyce K. Reynolds
      USC - Information Sciences Institute
      4676 Admiralty Way
      Marina del Rey, California  90292-6695

      Phone: [phone]

      ARPA mail: [e-mail]

   Most of the protocols mentioned here are documented in the RFC series
   of notes.  Some of the items listed are undocumented.  Further
   information on protocols can be found in the memo "Official
   ARPA-Internet Protocols" [114].  The more prominent and more
   generally used are documented in the "DDN Protocol Handbook" [46]
   prepared by the NIC.  Other collections of older or obsolete
   protocols are contained in the "Internet Protocol Transition Workbook
   [47], or in the "ARPANET Protocol Handbook" [48].  For further
   information on ordering the complete 1985 DDN Protocol Handbook,
   write: SRI International, DDN Network Information Center, Room EJ291,
   333 Ravenswood Avenue, Meno Park, California, 94025.  Or
   call: 1-800-235-3155.



Reynolds & Postel                                               [Page 1]



RFC 990                                                    November 1986
Assigned Numbers


   In the entries below the name and mailbox of the responsible
   individual is indicated.  The bracketed entry, e.g., [nn,iii], at the
   right hand margin of the page indicates a reference for the listed
   protocol, where the number ("nn") cites the document and the letters
   ("iii") cites the person.  Whenever possible, the letters are a NIC
   Ident as used in the WhoIs (NICNAME) service.

   The convention in the documentation of Internet Protocols is to
   express numbers in decimal and to picture data in "big-endian" order
   [131].  That is, fields are described left to right, with the most
   significant octet on the left and the least significant octet on the
   right.

   The order of transmission of the header and data described in this
   document is resolved to the octet level.  Whenever a diagram shows a
   group of octets, the order of transmission of those octets is the
   normal order in which they are read in English.  For example, in the
   following diagram the octets are transmitted in the order they are
   numbered.

                                    
    0                   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       |       2       |       3       |       4       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       5       |       6       |       7       |       8       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       9       |      10       |      11       |      12       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Transmission Order of Bytes

   Whenever an octet represents a numeric quantity the left most bit in
   the diagram is the high order or most significant bit.  That is, the
   bit labeled 0 is the most significant bit.  For example, the
   following diagram represents the value 170 (decimal).

                                    
                            0 1 2 3 4 5 6 7 
                           +-+-+-+-+-+-+-+-+
                           |1 0 1 0 1 0 1 0|
                           +-+-+-+-+-+-+-+-+

                          Significance of Bits

   Similarly, whenever a multi-octet field represents a numeric quantity


Reynolds & Postel                                               [Page 2]



RFC 990                                                    November 1986
Assigned Numbers


   the left most bit of the whole field is the most significant bit.
   When a multi-octet quantity is transmitted the most significant octet
   is transmitted first.














































Reynolds & Postel                                               [Page 3]



RFC 990                                                    November 1986
Network Numbers


                        ASSIGNED NETWORK NUMBERS

   The network numbers listed here are used as internet addresses by the
   Internet Protocol (IP) [46,101].  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 1-1-0.  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







Reynolds & Postel                                               [Page 4]



RFC 990                                                    November 1986
Network Numbers


      The fourth type of address, class D, is used as a multicast
      address [44].  The four highest-order bits are set to 1-1-1-0.

                           1                   2                   3