When I see a car that needs a /56 subnet then I’ll take your use case 
seriously. Otherwise, it’s just plain laughable. Yes, I could theorize a use 
case for this, but then I could theorize that someday everyone will get to work 
using jetpacks.

We have prefix delegation already via DHCP-PD, but some in the IPv6 world don’t 
even want to support DHCP, how does SLAAC do prefix delegation, or am I missing 
something else? I assume each car is going to be running as  RA? Given quality 
of implementations of IPv6 in embedded devices so far, I found that pretty 
ludicrous.

Seriously, the IPv6 world needs to get a clue. Creating new protocols and 
solutions at this point in the game is only making it more difficult for IPv6 
deployment, not less. IPv6 needs to stabilize and get going.. instead it seems 
everyone is musing about theoretical world where users need 64k networks. I 
understand the idea of not wanting to not think things through, but IPv6 is how 
many years old, and we are still arguing about these things? Don’t let the 
prefect be the enemy of the good.

----
Matthew Huff             | 1 Manhattanville Rd
Director of Operations   | Purchase, NY 10577
OTA Management LLC       | Phone: 914-460-4039
aim: matthewbhuff        | Fax:   914-694-5669

From: Harald Koch [mailto:c...@pobox.com]
Sent: Thursday, July 9, 2015 12:01 PM
To: Matthew Huff
Cc: Marco Teixeira; NANOG list
Subject: Re: Dual stack IPv6 for IPv4 depletion

On 9 July 2015 at 11:42, Matthew Huff <mh...@ox.com<mailto:mh...@ox.com>> wrote:
What am I missing? Is it just the splitting on the sextet boundary that is an 
issue, or do people think people really need 64k subnets per household?

One thing you're missing is that some of these new-fangled uses for IP 
networking will want to do their own subnetting. It's not "here's a subnet for 
the car", it's "here's a /56 for the car to break into smaller pieces as 
required".

A /56 isn't 256 subnets, it's 8 levels of subnetting (or 2 levels, if you're 
human and want to subnet at nibble boundaries). A /48 is 16 (or 4) levels. I 
have four vehicles, so I'd want to carve out a /52 for "the car network" to 
make the routing and security easier to manage, and leave room for expansion 
(or for my guests...)

One more consideration for you: we're currently allocating all IPv6 addresses 
out of 2000::/3. That's 1/8th of the space available. If we discover we've 
messed up with this sparse address allocation idea, we have 7/8ths of the 
remaining space left to do something different.

--
Harald

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