A crazy idea

Mon Jul 19 15:12:52 UTC 2021

On Monday, 19 July, 2021 14:04, "Stephen Satchell" <list at satchell.net> said:

> The allocation of IPv6 space with prefixes shorter than /64 is indeed a
> consideration for bigger administrative domains like country
> governments, but on the other end, SOHO customers would be happy with
> /96, /104 or even /112 allocations if they could get them.  (Just how
> many light bulbs, fridges, toasters, doorbells, phones, &c does SOHOs
> have?)  I would *not* like to see "us" make the same mistake with IPv6
> that was made with IPv4, handing out large blocks of space like so many
> pieces of M&M or Skittles candy.

Nay, nay, and thrice nay.  Don't think in terms of addresses for IPv6, think in terms of subnets.  I can't stress this enough, it's the big v4 to v6 paradigm shift - don't think about "how many hosts on this net", think about "how many nets".

It's potentially useful for SOHO users to have multiple subnets, particularly as they stick multiple devices in their home network that try to do PD from the upstream for each downstream function.  /56 for every SOHO is a fire-and-forget, you don't have to dick about with right-sizing anything, you don't have to evaluate requirements with the customer, you don't have to do all kinds of management system stuff to track who has what size, and it gives you some room for a couple of levels of hierarchy within the house.

Make all of the subnets /64s, and SLAAC etc Just Work too.

Wikipedia suggests a little short of 200M households in the US.  That's 28 bits of space to give a /56 to every household.  Let's assume ISPs are really bad at aggregation, so those bits are spread across multiple PoPs, multiple ISPs, etc, and we take 36 bits of space to actually allocate those.  (That's only in /56 in every 256 used, *lots* of room for sparse PoPs, sparse ISPs, etc).  Shift back 36 bits from a /56, we've used a /20 to number the entire US.

Same again for India.  3 of those for China.  It's all smaller from there for the rest of the world.  Maybe 100 or so /20s to number the entire world on the same plan.  There are a million /20s in the IPv6 address space.

We've got room to be sensible about assignments without repeating the IPv4 scarcity problem.

Cheers,
Tim.