RFC 990 (rfc990) - Page 2 of 75


Assigned numbers



Alternative Format: Original Text Document





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