to receive a number assignment.

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

        Electronic mail: IANA@ISI.EDU
        Phone: +1 310-822-1511




 
RFC 1700                    Assigned Numbers                October 1994


Most of the protocols 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, "Internet Official Protocol
Standards" (STD 1).

Data Notations

The convention in the documentation of Internet Protocols is to
express numbers in decimal and to picture data in "big-endian" order
[COHEN].  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
the left most bit of the whole field is the most significant bit.  When




 
RFC 1700                    Assigned Numbers                October 1994


a multi-octet quantity is transmitted the most significant octet is
transmitted first.

Special Addresses

There are five classes of IP addresses: Class A through Class E.  Of
these, Classes A, B, and C are used for unicast addresses, Class D is
used for multicast addresses, and Class E addresses are reserved for
future use.

With the advent of classless addressing [CIDR1, CIDR2], the
network-number part of an address may be of any length, and the whole
notion of address classes becomes less important.

There are certain special cases for IP addresses.  These special cases
can be concisely summarized using the earlier notation for an IP
address:

      IP-address ::=  { <Network-number>, <Host-number> }

         or

      IP-address ::=  { <Network-number>, <Subnet-number>,
                                                      <Host-number> }

if we also use the notation "-1" to mean the field contains all 1