[ppml] IPv6>>32

Geoff Huston gih at apnic.net
Mon May 9 16:56:16 EDT 2005

At 06:01 AM 10/05/2005, Tony Hain wrote:
>David Conrad wrote:
> > Michael,
> >
> > On May 9, 2005, at 9:39 AM, Michael.Dillon at radianz.com wrote:
> > >> The net result is that we're poised to burn through a /1 to a /4
> > >> of the IPv6 address space in the next 60 years based on our best
> > >> current guesses.  This makes me extremely nervous.
> > > I'm sorry but I cannot understand this sentiment at all.
> >
> > For me, the sentiment derives from the discomfort of knowingly
> > deploying something that is (arguably) broken.  I suspect if you went
> > back in time and asked Vint or Bob Kahn or any of the other original
> > net geeks if they thought IPv4 would ever really be at risk of
> > running out, they'd laugh at you.
>Burning through a /4 in 50 years is consistent with original assumptions, as
>is the point that we have 3/4 of the space set aside for different
>allocation approaches if the first proved wrong. It is not that people
>didn't learn anything from the first time around, it is just that some want
>to be more conservative than others.

The IPv6 roundtable presentation at ARIN XV explicitly placed quite a high 
level of uncertainly on that number of cumulative consumption Tony, and the 
presentation explicitly noted that the outcome was somewhere between a /1 
and a /4. Not, that's not a /4, that's somewhere between a /1 and a /4.

Also, just to be mathematically on the right track here a /4 is 1/16 of the 
number space, while a /2 is one quarter of the address space. So, to 
rephrase your comment, if the cumulative consumption is a /4 then there is 
15/16ths of the space that could, in theory, be used for different 
allocation approaches.

However, its sensible to also note that if we think that "installed base" 
is an argument today in terms of the pain associated with changing the 64 
bit length for the device identifier, just wait until the installed base of 
end sites gets to the 30 billion mark that is commensurate with a /4 
consumption under current policies. Now 30 billion end sites  is _really_ 
an installed base, and its inertial impetus would say to me that at that 
stage your wriggle room for the remaining space is pretty much a lost 
opportunity. So if we are having trouble now in looking at the global 
identifier on the basis of the inertial mass of already deployed systems 
and services, then you cannot also put forward the proposition that we can 
change things once we've deployed 30 billion end site instances of the same.

So I'm afraid that "we've still got future wriggle room in the future so 
don't worry about it now" is not an approach that I can accept easily - if 
at all. At that point the late comers will be complaining that they are 
exposed to tougher and more constrained policies that are deployed at a 
higher cost than that of the early adopters - and if all this sounds 
hauntingly familiar in reference to the current debates about national 
interests and highly populous economies and various address policy 
frameworks, then it should. I'm afraid that there's an increasing cynicism 
out there about the refrain of "don't worry we'll fix it once its visibly 
broken" with respect to address policies. We should at this point be 
striving to instill some broad confidence in the proposition that we can 
provide a stable and enduring platform for the world's communications needs.



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