IP Address | How were IPv4 addresses distributed ?

 How were IPv4 addresses distributed ?

IANA assigns addresses based on globally agreed-upon rules, or policies. The key policy elements for IPv4 were:

■■ RIRs received IPv4 blocks in /8 units from IANA.
■■ RIRs could receive an additional block when they had just one half of a block left.
■■ The number of /8 units RIRs received was based on a formula established by IANA.

Two policies governed the allocation of IPv4 addresses to the RIRs. The regular policy was called the Policy for Allocation of IPv4 Blocks to Regional Internet Registries and governed how IPv4 addresses were allocated to RIRs since April 2005. The second, called the Global Policy for the Allocation of the Remaining IPv4 Address Space, governed how the last five IPv4 /8s were allocated. It was ratified in March 2009.

The regular policy

            The regular policy contained a formula for determining when an RIR qualified for additional IPv4 address space and how much address space the RIR could receive. To qualify for additional space, the RIR had to meet one of the following qualifications: it must have had less than 8 million addresses, which is less
than half of a /8, left in its stock of addresses that it could distribute, or it must have lacked sufficient
space to meet its members’ needs for the coming nine months.

Defining the variables 

                  The variables in the policy’s formula were available space and necessary space. All an RIR’s IPv4 address space was considered available for allocation unless the space was a reservation that would expire
within the coming three months, or was fragmented.
A reservation is a block of address space set aside for a particular network operator at a future date. RIRs
sometimes reserve particular blocks for network operators that frequently request more address space. By doing so, the RIR can ensure a sequential allocation in a single, contiguous block, and the network operator can announce these reserved spaces as a single route, reducing the burden on the routing system. Fragmented spaces are blocks of address space that are smaller than the minimum allocation size set by the RIRs’ policy-making community.

            The policy’s formula considered recent history and then projected forward to determine how much
address space an RIR might need in the future. The formula worked this way: First, it used simple
averaging to determine the number of addresses allocated per month during the past six months.
This average helped determine how much space an RIR was expected to need in the near term. If
the RIR’s available space was not enough for the next nine months of allocations, the RIR qualified for
additional address space.

Special facts

           The policy also allowed special facts to be taken into account when calculating how much additional IPv4 address space an RIR qualified to receive. These special facts might have applied if there was a new regional policy or external factors, such as new infrastructure, new services within the region,
technological advances or legal issues. In all cases, the RIR was required to explain the change in
consumption rate or the impact of the new policy, or it had to provide an analysis of the external factors.
If the RIR’s data was not sufficiently clear, IANA could question it. Special facts were almost never used to support requests for additional address space. In fact, RIRs tended to request less address space than they could justify.

The calculation

         Once this data was collected, the calculation could go forward.

Necessary Space = Average Number of Addresses Allocated Monthly during the Past 6 Months x Length of Period in Months 

           Although each RIR provided all this data to ICANN’s IANA Department with its request, most of the data was published every day in a standard format log file, and was mirrored on the IANA FTP site. But whether the calculation was done by ICANN staff or by an observer, using the data published by the
RIRs made calculating the results simple. The numbers could be entered in a spreadsheet that calculated how much space an RIR could receive.