Re: minimum IPv6 announcement size

[Darren Pilgrim <nanog () bitfreak org>]

On 9/26/2013 1:07 PM, joel jaeggli wrote:
> On Sep 26, 2013, at 12:29 PM, Darren Pilgrim <nanog () bitfreak org>
> wrote:
>
> > On 9/26/2013 1:52 AM, bmanning () vacation karoshi com wrote:
> > > sounds just like folks in 1985, talking about IPv4...
> >
> > The foundation of that, though, was ignorance of address space
> > exhaustion.  IPv4's address space was too small for such large
> > thinking.
>
> The first dicussion I could find about ipv4 runnout  in email
> archives is circa 1983
>
> > IPv6 is far beyond enough to use such allocation policies.
>
> There are certain tendencies towards profligacy that might
> prematurely influence the question of ipv6 exhaustion and we should
> be on guard against them… allocating enough /48s as part of direct
> assignments  is probably not one of them.

That's just it, I really don't think we actually have an exhaustion risk 
with IPv6.  IPv6 is massive beyond massive.  Let me explain.

We have this idea of the "/64 boundary".  All those nifty automatic 
addressing things rely on it.  We now have two generations of hardware 
and software that would more or less break if we did away with it.  In 
essence, we've translated an IPv4 /32 into an IPv6 /64.  Not great, but 
still quite large.

Current science says Earth can support ten billion humans.  If we let 
the humans proliferate to three times the theoretical upper limit for 
Earth's population, a /64 for each human would be at about a /35's worth 
of /64's.  If we're generous with Earth's carrying capacity, a /36.

If we handed out /48's instead so each human could give a /64 to each of 
their devices, it would all fit in a single /52.  Those /48's would 
number existance at a rate of one /64 per human, one /64 per device, and 
a 65535:1 device:human ratio.  That means we could allocate 4000::/3 
just for Earth humans and devices and never need another block for that 
purpose.

That's assuming a very high utilisation ratio, of course, but really no 
worse than IPv4 is currently.  The problem isn't allocation density, but 
router hardware.  We need room for route aggregation and other means of 
compartmentalisation.  Is a 10% utilisation rate sparse enough?  At 10% 
utilisation, keeping the allocations to just 4000::/3, we'd need less 
than a single /60 for all those /48's.  If 10% isn't enough, we can go 
quite a bit farther:

- 1% utilisation would fit all those /48's into a /62.
- A full /64 of those /48's would be 0.2% utilisation.
- 0.1%? We'd have to steal a bit and hand out /47's instead.
- /47 is ugly.  At /52, we'd get .024% (one per 4096).

That's while maintaining a practice of one /64 per human or device with 
65535 devices per human.  Introduce one /64 per subnet and sub-ppm 
utilisation is possible.  That would be giving a site a /44 and them 
only ever using the ::/64 of it.

Even with sloppy, sparse allocation policies and allowing limitless 
human and device population growth, we very likely can not exhaust IPv6.