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Graph Shows Decline of IPv4 Has Been Mostly Linear

Mirjam Kuehne

As the free pool of IPv4 addresses reaches its end, we looked at the evolution of the amount of unassigned IPv4 address space over time. By 'unassigned', we mean address space not yet allocated to a Local Internet Registry (LIR) or assigned to an end user. LIRs are typically Internet Service Providers or enterprises operating an IP network.

See our findings in the graph below.

The graph shows that the decline of IPv4 has been mostly linear. This means that the Regional Internet Registries (RIRs) have been allocating roughly ten /8s1 each year since 2004. There was a small decrease in allocations in 2008 — due undoubtedly to the economic crisis — before accelerating again in mid-2009.

Thirty-three unassigned /8's of IPv4 addresses remain as of 1 October 2010. An overly simplistic extrapolation would mean that the RIRs still have three years left to hand out IPv4 address space. This is no reason to relax. We have clearly entered the last phase of available IPv4 address space. In 2010 the need for IPv4 addresses exceeded the long term average. RIRs handed out thirteen /8s in the last twelve months. If this trend continues or accelerates, the lifespan of the unassigned IPv4 address space will be significantly shorter.

Also, due to the difference in the regional communities, it is likely that one region will run out of IPv4 space while another may still have more than one /8 left.

Three years is really the upper limit. An exact run-out date is difficult to forecast because it doesn't only depend on mathematical modeling but also on address policies.

One might wonder: 'Why has the number of allocations been so stable over time when the number of LIRs has been increasing at the same time?'. There is no clear answer to this question. The reason is likely to be a combination of the increased deployment of Network Address Translations (NATs) and the increased relevance of IPv4 conservation within the RIR communities over time.
For more information about the method used, please refer to "Interesting Graph — IPv4 Unassigned

1 One /8 of IPv4 address space contains 128 networks (27). Each of these networks contains 16.777.216 addresses (224).

By Mirjam Kuehne

Related topics: IP Addressing, IPv6, Networks, Regional Registries


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Different Numbers Lee Howard  –  Oct 12, 2010 8:42 AM PDT

Your consumption numbers are different than those provided by the NRO, which show dramatic consumption increases over the past ten years.  IANA shows twelve /8s allocated in the first nine months of 2010.

You also assume that Class E space (240/8 and higher) is available for assignments.  Broad consensus is that this space is not generally usable.

After adjusting for consumption rates provided by the NRO, and including only global unicast space, IANA has 14 /8 remaining today.  Knowing that IANA will allocate the last five /8 all at once, the question is, "How long will the next nine /8 last?"

Re: Different Numbers Mirjam Kuehne  –  Oct 13, 2010 3:23 AM PDT

Hi Lee,

I don't see a huge difference between the NRO statistics and the statistics we provided in this article. Yes, one RIR's allocation rate has increased quite dramatically over the last few years, but others have decreased at the same time. There is also address space that has been returned to the RIRs.

But please note that this is a different way of looking at it: The NRO stats show the number of addresses allocated, we have looked at the number of addresses still either unallocated or unassigned.

Also, we have not just looked at the addresses held by the IANA, but at all addresses in the entire RIR system. The RIRs also hold address space that is not yet assigned and are handing it out according to current policy. As described in the background article on RIPE Labs, the legacy address space (pre-RIR system) also contains holes that can be considered unassigned. These blocks are not necessarily whole /8s, but smaller blocks which we included in the total.

Class E space has not been included in our count. We subtracted those addresses from the start (the methodology is described on RIPE Labs).

The intention was not to predict exhaustion dates. We just wanted to show how things evolved over the last years and how much is left "today".


Tracking the active and inactive IPs is more prudent and accurate Jothan Frakes  –  Oct 15, 2010 9:41 AM PDT

The scarcity of IPv4 address space and the push for IPv6 has created a demand within the secondary market in the IPv4 Legacy allocations.

Allocation of new blocks is certainly important to track, but I think it may not capture the activity where legacy /8's that have been long dark are being chopped up and used by their holders via auctions or other manners.

If one only tracks the allocated space via the Regional (ARIN/RIPE/etc) RIRs, the aftermarket activity from legacy allocations gets missed. 

This secondary activity can be large or small activity and it is really only visible if one actually downloads and parses the routing tables, which is not trivial.

Just saying that the numbers that NRO / LIR publish MAY not capture some additional demand fulfillment.

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