[ppml] Policy Proposal: Decreasing Exponential Rationingof IPv4 IP Addresses

Iljitsch van Beijnum iljitsch at muada.com
Fri Aug 31 16:10:46 EDT 2007

On 31-aug-2007, at 16:55, <michael.dillon at bt.com> wrote:

>> The only thing that looks pretty solid is that
>> there's almost always growth in the number of addresses used
>> up per year. Anything else only persists for a few years and
>> then changes.

> Those things that persist for a few years are the trends.

A few = generally 2 or 3 years. Is that enough to call a trend?

> And the
> changes have been explained due to macro events (CIDR introduction,
> telecoms collapse) so even though the trends go through step changes,
> they are still trends.

If you can tell the trends from the macro events, please do so  
because as far as I know, nobody else has been able to.

> One could still do a worst-case scenario based on
> the pre telecoms collapse trend

I guess that would be going from 86 million in 2001 to 69 million in  

> and then estimate the probability that
> macroeconomic events will lead to that scenario. You then have an
> estimated runout date, and a probability that it will occur.

Worst case that we've seen is almost doubling from 43 million new  
addresses in 1999 to 81 million in 2000. Perspective: 1998 was 60 and  
2001 86 million.

You can arrive at pretty much any outcome by just selecting the right  
start date. From 98 million in 1996 to 170 in 2006 is 5.7% growth per  
year but starting in 1999 results in 21.7% and 2002 25.3%. Now if all  
of this had been going on for 100 or even 30 years it would probably  
be possible to see a long-year trend. But 1995 was the first year  
with growth after the introduction of CIDR so we only have 12 years.  
It's just not enough to come up with something better than 5 - 25 %  
growth per year = running out between Q3 2011 and Q3 2013.

However, you can't predict a run on the bank, hoarding and all kinds  
of other interesting end games by looking at the past.

> There are some very learned people who have spent their entire life
> studying forecasting methodology. If someone were to point out  
> flaws in
> Tony's or Geoff's methodology based on the published literature, that
> would be valuable. I would also expect Tony and Geoff to fix those
> flaws.

Let me put it this way: would either of them care to publish an error  
margin to go along with their prediction? Or run the numbers on  
historical data and see how well the predictions fit what actually  

> I was hoping that someone like you would take up the
> challenge of finding another data source and producing yet another
> forecast.

I don't think there's another source of data. However, if you want I  
can split the difference between Q3 2011 and Q3 2013, which brings us  
back to my "London olympics" prediction from a few days ago.

> It's easy to wave your hands and be a sceptic but that doesn't lead us
> anywhere.

Who says we're going anywhere, and if we are, whether we're actually  
getting there? :-)

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