Waste will kill ipv6 too

Mark Andrews marka at isc.org
Wed Dec 20 21:57:35 CST 2017

When the IETF decided on 128 bit addresses it was taking into consideration /80 sized subnet.  Prior to that it was looking at a 64 bit address size and allocating addresses the IPv4 way with lots of variable sized networks.  This was changed to /64 subnets to accomodate 64 bit MAC.  After that there was discussion about how many subnet should be enough for 99.99% of sites which gave /48 per site using /64 sized network.  That 281474976710656 sites or 35184372088832 out of the /3 we are currently allocating from.

Now there are very few sites that need 65536 subnets and those that do can request additional /48’s.

Now if you assume the earth’s population will get to 25B, and every person is a site, that still leaves 35159372088832 sites.
And if each of those people also has a home and a vehicle, that still leaves 35109372088832 sites.

Handing out /48’s to homes was never ever going to cause us to run out of IPv6 space.  Even if the homes are are connected to multiple providers there isn’t a issue.


> On 21 Dec 2017, at 7:57 am, William Herrin <bill at herrin.us> wrote:
> On Wed, Dec 20, 2017 at 1:48 PM, Mel Beckman <mel at beckman.org> wrote:
>> I won’t do the math for you, but you’re circumcising the mosquito here. We
>> didn’t just increase our usable space by 2 orders of magnitude. It’s
>> increased more than 35 orders of magnitude.
> Hi Mel,
> The gain is just shy of 29 orders of magnitude. 2^128 / 2^32 = 7.9*10^28.
> There are 2^128 = 3.4*10^38 IPv6 addresses, but that isn't 38 "orders of
> magnitude." Orders of magnitude describes a difference between one thing
> and another, in this case the IPv4 and IPv6 address spaces.
> Using a /64 for P2P links is no problem, really. Worrying about that is
>> like a scuba diver worrying about how many air molecules are surrounding
>> the boat on the way out to sea.
> It's not a problem, exactly, but it cuts the gain vs. IPv4 from ~29 orders
> of magnitude to just 9 orders of magnitude. Your link which needed at most
> 2 bits of IPv4 address space now consumes 64 bits of IPv6 address space.
> Then we do /48s from which the /64s are assigned and we lose another 3 or
> so orders of magnitude... Sparsely allocate those /48s for another order of
> magnitude. From sparsely allocated ISP blocks for another order of
> magnitude. It slips away faster than you might think.
> Regards,
> Bill Herrin
> -- 
> William Herrin ................ herrin at dirtside.com  bill at herrin.us
> Dirtside Systems ......... Web: <http://www.dirtside.com/>

Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742              INTERNET: marka at isc.org

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