Class A Subnet Experiment
RFC 1797

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Network Working Group                                               IANA
Request for Comments: 1797                                           ISI
Category: Experimental                                        April 1995

                       Class A Subnet Experiment

Status of this Memo

   This document defines an Experimental Protocol for the Internet
   community.  This does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

Discussion

   There appears to be some interest in experimenting with subnetting
   the class A addresses.

   There is some evidence that not all the routing software in use will
   deal correctly with subnetted class A addresses.  It also appears
   that actual use of subnetted class A addresses may be necessary in
   the not too distant future.  It is suggested that conducting an
   experiment now to identify and fix any software that does not
   properly handle subnetted class A addresses would be useful and
   important.

   To further this experiment the IANA will temporarily designate the
   class A network number 39 to be used in the following way:

   The high order octet of the 4-octet IPv4 address is the class A
   network number 39.  There are two cases for low order 24 bits.

   Case 1:

      In the first case, the high order bit of these 24 bits is zero and
      the next 15 bits are the low order 15 bits of a previously
      assigned Autonomous System number (AS), as registered by a network
      registry and listed in the RWhois database system.

      Using the AS number in this way allows the experiment to get
      underway quickly in that it automatically allocates some addresses
      to each service provider and does not require a registration step.

      One concern is that this might cause a run on AS numbers, since by
      getting an AS number you automatically get some address space.
      This concern should be offset by the fact that the amount of
      address space one gets under this plan is the same as one class C

IANA                                                            [Page 1]
RFC 1797               Class A Subnet Experiment              April 1995

      network number (and it should be easier to get a single class C
      allocated than to get an AS number allocated), and that this is a
      limited time experiment so that these addresses will be temporary.

      The low order octet of the 4-octet IPv4 address is for local use.
      It is expected that an address of this form will be used to
      identify a specific publicly accessible Internet host.

                +--------+-+-------+--------+--------+
                |   39   |0| low 15 bits AS | local  |
                +--------+-+-------+--------+--------+
   Case 2:

      In the second case, the high order bit of these 24 bits is one,
      and the remaining 23 bits are assigned by the IANA (currently
      reserved for future use).

                +--------+-+-------+--------+--------+
                |   39   |1| variable prefix + local |
                +--------+-+-------+--------+--------+

      The general intent is to find a way to assign to experimenters
      prefixes of differing lengths so that a variety of experiments can
      be conducted with the prefix/local-address boundary at different
      points.

   It is not intended that either of these address allocation schemes is
   the model for how subnetted class A addresses will be actually
   allocated in the future.

   It is expected, to make the experiment interesting, that some
   providers will use these addresses for servers supplying popular
   material via the Web or FTP.

   For example, if the service provider registered to use AS 690 wished
   to use this style of address to provide access to a server of popular
   information on local host 7, the address would be:

                +--------+--------+--------+--------+
                |   39   |    2   |   178  |    7   |
                +--------+--------+--------+--------+

IANA                                                            [Page 2]
RFC 1797               Class A Subnet Experiment              April 1995

   The support for DNS name and address resolution should be provided.
   For example, if Alternet wanted to put up a database of interesting
   information using the hostname "Interesting.Alter.Net" using the
   address 39.2.189.7, they would need to put the name to address
   mapping in their name server using the A record

        Interesting.Alter.Net. IN A 39.2.189.7

   Similarly, the address to name PTR record should be supported

        7.189.2.39.IN-ADDR.ARPA. PTR Interesting.Alter.Net.

   which means that the 189.2.39 branch of the IN-ADDR tree would be
   delegated to Alternet for the purposes of this experiment.

   To support this, the 39.IN-ADDR.ARPA branch is delegated to the IANA
   to be managed at ISI.  The nameserver for this branch is