nanog mailing list archives

Re: A crazy idea


From: "james.cutler () consultant com" <james.cutler () consultant com>
Date: Tue, 10 Aug 2021 18:34:30 -0400

Thank you, Tim.

I have often suggested that clear business purposes should drive implementation of technology. Every cogent analysis of 
IPv6 shows that there are enough addresses that we need not worry about running out of addresses for many decades. Even 
swarms of devices should not seriously impact global IPv6 usage as they will have their own collision domain (/64, I 
presume). Norbert Weiner’s book Science and Cyphernetics (The Human Use of Human Beings) suggests than one should 
optimize human productivity and let the technology handle the grunt work. The human cost of micro-managing IPv6 
assignments would be obscenely prohibitive. 

In well over 15 years on this topic, I have yet to find a reason for making every customer encounter and configuration 
more complicated than as described by Tim. It just does not make economic sense.
-
James R. Cutler 
Top posted because Apple keeps changing Mail and I am Lazy an engineer at heart.
james.cutler () consultant com <mailto:james.cutler () consultant com>

On Jul 19, 2021, at 11:12 AM, tim () pelican org wrote:

On Monday, 19 July, 2021 14:04, "Stephen Satchell" <list () 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.




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