Network Working Group                                         K. Siyan
Request for Comments: 1365                   Siyan Consulting Services
                                                        September 1992

                    An IP Address Extension Proposal

Status of This Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard.  Distribution of this memo is
   unlimited.

Abstract

   This RFC suggests an extension to the IP protocol to solve the
   shortage of IP address problem, and requests discussion and
   suggestions for improvements.

1. Introduction and Background

   The Internet community has a well-developed, mature set of protocols
   that have been quite successful in providing network and transport
   services to users. However, because of the spectacular success of the
   TCP/IP protocols and the number of networks that desire connection to
   the Internet, there is a shortage of network numbers that can be
   assigned.

   The current network addressing scheme uses a 32-bit IP address that
   has a network part and a local address part.  The division between
   the network part and the local address part has been defined in terms
   of 5 address classes: class A, B, C, D, E.  Of these, only class A,
   B, C addresses are assigned to hosts. Class D is used for
   multicasting and class E is reserved.

   Class A has the highest order bit set to 0, a 7 bit network number
   and a 24 bit host address.

   Class B has the two higher order bits set to 10, a 14 bit network
   number and a 16 bit host address.

   Class C has the three higher order bit set to 110, a 21 bit network
   number and a 8 bit host address.

   Class D has the four higher order bits set to 1110.

   Class E has four higher address bits set to 1111.

   Increasing the size of the IP address field to more than 32 bits
   would solve the problem, but at the expense of making a new IP header
   definition that would be incompatible with the existing base of IP
   implementations. OSI based solutions such as using CLNP have been
   proposed but would take time to implement.

2. Proposal for IP extension

   The IP header format should not be modified to minimize the changes
   necessary for supporting the address extensions that are proposed in
   this RFC. Instead an "escape" mechanism can be used to specify larger
   address. The IP header length field is 4 bits and this allows a
   maximum of fifteen 32-bit words where each word is 4 octets.  The
   minimum size of the IP header without options is 5 words, which
   leaves 10 words for options.  One can reserve 6 words (24 octets) for
   the normal options and leave the remaining (4 words or 16 octets) for
   a new option type that specifies an extended address. The details of
   this mechanism are discussed below.

   Class E should be defined with the its five high order bits set to
   11110. Its current definition is that four 1's in the most
   significant bits represent a class E address.

   A new class F is proposed with its six high order bits set to 111110.
   The new class F address would be placed in the same locations that
   are used for source and destination IP address in the IP header, but
   would specify that part of the addressing information is in the
   options part of the IP header. This is illustrated in the figure
   below:

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Ver.  | IHL   |   TOS         |   Total Length                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Identification            |Flags|   Fragment Offset       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|1|1|0| Offset| Reserved  | Source IP address part 1      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|1|1|0| Offset| Reserved  | Destination IP address part 1 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                            Options                            :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   : SADDR Code    |Len adr. part 2| Source IP address part 2      :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   : DADDR Code    |Len adr. part 2| Destination IP address part 2 :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                            Data                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The "Offset" field specifies the offset in words from the beginning
   of the IP header where the second part of the IP address is located.
   Its purpose is to avoid searching the options part for addressing
   information. The address in the options part is in the Type-Length-
   Value form for consistency with other IP options that are found in
   this part.  The "Len adr. part" indicates the length of the second IP
   address part in octets. The lengths should be defined so that the
   second part of the IP address ends on a word boundary. For example,
   the possible length values are 4, 8 octets.  It is proposed that new
   IP option codes be used for the SADDR and DADDR codes respectively.

   The IP address is the 2 bytes in the fixed IP header part plus the
   address field defined in the options part.

   If the "Len adr. part" field has a value of 4, the new class is
   designated as the F-4 class (Class F with IP address length of 4
   octets).

   If the "Len adr. part" field has a value of 8, the new class is
   designated as the F-8 class (Class F with IP address length of 8
   octets).

   Each of the F-4 and F-8 IP address class can be further subdivided
   into a network number and a host number field in a manner that is
   similar to the current IP addressing scheme.

   The sub-class definitions for F-4 class are shown below. Though the 4
   octets are drawn contiguously, the first 2 octets and the last 2
   octets are not contiguous in the IP header.

   Class F-4A has the highest order bit set to 0, a 7 bit network number
   and a 24 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| net number  |  local part                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-4B has the two higher order bits set to 10, a 14 bit network
   number and a 16 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|0|      net number           |   local part                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-4C has the three higher order bit set to 110, a 21 bit
   network number and a 8 bit host address.

      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |1|1|0|      net number                         | local part    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-4D has the four higher order bits set to 1110. Class F-4D is
   reserved for multicasting.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|0|       |       multicast                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   The sub-class definitions for F-8 class are shown below. Though the 8
   octets are drawn contiguously, the first 2 octets and the last 6
   octets are not contiguous in the IP header.

   Class F-8A has the highest order bit set to 0, a 7 bit network number
   and a 56 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0| net number  |          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8B has the two higher order bits set to 10, a 14 bit network
   number and a 48 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|0|      net number           |   local part                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8C has the three higher order bit set to 110, a 21 bit
   network number and a 40 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|0|      net number                         | local part    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8D has the four higher order bits set to 1110, a 28 bit
   network number and a 32 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|0|                  net number                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8E has the five higher order bits set to 11110, a 35 bit
   network number and a 24 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|1|0|                net number                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   net number  |          local part                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8F has the six higher order bits set to 111110, a 44 bit
   network number and a 16 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|1|1|0|              net number                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          net number           |        local part             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Class F-8G has the seven higher order bits set to 1111110, a 49 bit
   network number and a 8 bit host address.

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |1|1|1|1|1|0|              net number                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 net number                    |  local part   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3. Interoperability Issues

   If the new class F address is seen by a host that does not support it
   the IP datagram will be ignored. So communication will not be
   possible with existing hosts, but the amount of modification for
   existing hosts is much less than implementing an entirely different
   IP header structure or a different protocol.

   The receiving host must be modified to contain the following code
   sketched below:

        if (Destination_IP_address & 0xFC000000 == 0xF8000000)
        {

             /* New extended class F address */
             Class_F_Processing(Destination_IP_address);

         }

   The Class_F_Processing() procedure can be defined in a separate
   module. There will be other changes required to communicate the
   results of processing the class F address to the main IP processing
   module but they should not be so extensive.

Security Considerations

   Security issues are not discussed in this memo.

Author's Address

   Karanjit Siyan
   Siyan Consulting Services
   49 Taurus Road, Box 960
   North Glastonbury
   Emigrant, Montana 59027

   Phone:  406-333-4491

   EMail:  72550.1634@compuserve.com