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Re: "It's the end of the world as we know it" -- REM
From: Geoff Huston <gih () apnic net>
Date: Wed, 24 Apr 2013 09:44:09 +1000

On 24/04/2013, at 8:10 AM, Andrew Latham <lathama () gmail com> wrote:

On Tue, Apr 23, 2013 at 5:41 PM, Valdis Kletnieks
<Valdis.Kletnieks () vt edu> wrote:
I didn't see any mention of this Tony Hain paper:

http://tndh.net/~tony/ietf/ARIN-runout-projection.pdf

ARIN predicted to run out of IP space to allocate in August this year.

Are you ready?


The prediction of runout business is extremely hard. All of these predictions are based on the basic premise that what 
happened yesterday will most likely happen tomorrow. And in a world of very large populations this is highly likely - 
the larger the population its often the case that the smaller the impact of individual variations in behaviour. That 
means that once you get a very large population you'd expect a relatively low level of uncertainty in trend-based 
predictive models.

But the world of addresses is not so well behaved. For some years now we've seen the address world bifurcate into a 
small number of very large actors and a large number of much smaller actors. In the address world it was observed that 
less than 1% (its closer to around 0.5%)  individual allocations account for more than half of the number of allocated 
addresses. This becomes a problem in the predictive models, as the dominant factor in address consumption is now the 
actions of some 20 or so very large entities. If they all fronted at the registry's front doors and asked for a three 
month allocation, and do so again in 90 days, and so on, then its pretty obvious that ARIN's remaining 40M addresses 
would not last more than one or two iterations of this cycle.

But what has been apparent in the ARIN region since the IANA runout of February 2011 has not been panic, but restraint. 
If you look at the run-down' of the address pool in ARIN over time (http://www.potaroo.net/tools/ipv4/arin-pool.png), 
you could certainly make the case that there was a pronounced run on address resources in ARIN in the last quarter of 
2010, but it all changed in 2011. The ensuing 14 months following IANA runout, through 2011 and early 2012, saw a 
pronounced change in the region, and ARIN's address consumption in that period slowed down to a consumption rate that 
got as low as 1M addresses per month. This coincided in a change in the address allocation policy to reduce the time 
horizon of "demonstrated need" from 12 months to 3 months, but that factor alone would not account for the entirety of 
this slow down in the address consumption rates over this 14 month period. 

Following a single largish allocation in early 2012 we've seen the ARIN address consumption rate increase somewhat, and 
the average rate of address consumption is currently around 2M addresses per month. If this rate of address consumption 
continues, the ARIN will reach its last /8 in early 2014, and if this rate persists, then the registry will exhaust its 
pool around the end of that year, or early 2015.

But given the uncertainty factors here as they relate to the distribution of large and small consumers in this area and 
changing sentiment about whether or not panic is a factor in address demands, I'd have to comment that the uncertainty 
factor of any prediction is high. Its quite plausible that exhaustion could occur some 6 - 9 months earlier than these 
dates. 

However, personally I find it a little hard to place a high probability on Tony's projected exhaustion date of August 
this year. I also have to qualify that by noting that while I think that a runout of the remaining 40 M addresses 
within 4 months is improbable, its by no means impossible. If we saw a re-run of the address consumption rates that 
ARIN experienced in 2010, then it's not outside the bounds of plausibility that ARIN will be handing out its last 
address later this year. 

thanks,

Geoff




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