It doesn't take any OS upgrades for "getting everything to work on
IPv6".  All the OS's and routers have supported IPv6 for more than a
decade.

There are lots of vendors, both inside and outside the networking space, that have consistently released products with non-existant or broken IPv6 implementations. That includes smaller startups, as well as very big names. An affirmative choice is often made to make sure v4 works , get the thing out the door, and deal with v6 later, or if a big client complains. 

To be completely fair, some of those vendors also mess up IPv4 implementations as well, but in my experience , v4 stuff is more often 'vanilla' coding issues, whereas v6 mistakes tend to be more basic functional errors, like handling leading zeros correctly. 



On Wed, Mar 9, 2022 at 4:17 AM John Gilmore <gnu@toad.com> wrote:
John Levine <johnl@iecc.com> wrote:
> FWIW, I also don't think that repurposing 240/4 is a good idea.  To be
> useful it would require that every host on the Internet update its
> network stack, which would take on the order of a decade...

Those network stacks were updated for 240/4 in 2008-2009 -- a decade
ago.  See the Implementation Status section of our draft:

  https://datatracker.ietf.org/doc/draft-schoen-intarea-unicast-240/

Major networks are already squatting on the space internally, because
they tried it and it works.  We have running code.  The future is now.
We are ready to update the standards.

The only major OS that doesn't support 240/4 is Microsoft Windows -- and
it comes with regular online updates.  So if IETF made the decision to
make it unicast space, most MS OS users could be updated within less
than a year.

> It's basically
> the same amount of work as getting everything to work on IPv6.

If that was true, we'd be living in the IPv6 heaven now.

It doesn't take any OS upgrades for "getting everything to work on
IPv6".  All the OS's and routers have supported IPv6 for more than a
decade.

Whatever the IPv6 transition might require, it isn't comparable to the
small effort needed to upgrade a few laggard OS's to support 240/4 and
to do some de-bogonization in the global Internet, akin to what CloudFlare
did for 1.1.1.1.

        John