RFC 1365 (rfc1365) - Page 2 of 6

An IP Address Extension Proposal

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RFC 1365                 An IP Address Proposal           September 1992


   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                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




Siyan
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