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. Mark > On 21 Dec 2017, at 7:57 am, William Herrin <b...@herrin.us> wrote: > > On Wed, Dec 20, 2017 at 1:48 PM, Mel Beckman <m...@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 ................ her...@dirtside.com b...@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: ma...@isc.org
