IPv4 Reclamation Algorithm
==========================

OVERVIEW

In May 2012, the ICANN Board ratified the Global Policy for Post Exhaustion
IPv4 Allocation by IANA.  This policy called for the establishment of a
Recovered IPv4 Pool, which contains fragments leftover in the IANA and
space that has been returned to the IANA by other means. The policy also
called for IANA to make allocations from the Recovered IPv4 Pool once the
pool is declared active.

The pool was declared active on 20 May 2014 when the first RIR had less 
than a /9 of IPv4 space in its inventory. The pool will also be declared 
active during “IPv4 allocation periods”, 6-month periods following 1 March
or 1 September in each year.

ICANN reported that we will use an open-source software program to 
perform the address selection process. This code implements the IPv4 
reclamation policy.

REQUIREMENTS

The Global Policy calls for the following:

    When the Recovered IPv4 Pool is first activated and at the beginning
    of each subsequent IPv4 allocation period, we will use software to
    select 5 IPv4 allocation units (one for each RIR) from the current
    IPv4 Recovered pool.

    An IPv4 allocation unit is 1/5 of Recovered IPv4 pool, rounded down
    to the next CIDR (power-of-2) boundary.

    The minimum "IPv4 allocation unit" size will be a /24. If the
    calculation used to determine the IPv4 allocation unit results in a
    block smaller than a /24, the IANA will not distribute any addresses
    in that IPv4 allocation period.

The software should use the published ipv4-recovered-address-space
registry XML file as input and output an updated XML file for check-in to
the repository. Ideally, the software should try to allocate RIRs address
space within /8s they already manage, based on the distribution in the
ipv4-address-space registry.

METHODOLOGY

The algorithm determines the number of addresses that must be assigned
to each RIR using the Global Policy. It determines the available ranges
that can be re-allocated using the IANA recovered IPv4 address registry.
It also determines a preference for each range using the current "WHOIS"
records in the IPv4 address registry. The WHOIS record is a good indicator
of which RIR is responsible for the covering /8 for a particular IP
address.

Based on these inputs, the algorithm iterates through each RIR and finds
the best record to satisfy their need. Allocations are weighted toward
(a) allocations that would be drawn from a range for which the
RIR is responsible for the covering /8; (b) allocations that are larger;
and (c) allocations that are the exact size of the needed space.

HOW TO USE

The algorithm is implemented as a command-line tool. Invoking the tool
without arguments will fetch the most recent version of the two input
registries from the IANA website. You can alternatively specify either a
file-path or a URL as command line arguments to nominate alternate inputs.

Using the "-o" or "--output" flags will save a revised version of the
recovered IPv4 registry updated to reflect the new allocations. Note that
allocations generated by this software will only take effect once the
revised registries are published officially by ICANN.

LICENSE

Copyright (c) 2014, Internet Corporation for Assigned Names and
Numbers. All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.

    * Neither the name of the ICANN nor the names of its contributors
      may be used to endorse or promote products derived from this
      software without specific prior written permission.

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