IPv4 servers are reachable by IPv6-only clients. ipv6test.google.com famously has only an A (IPv4) record for a reason.
> God knows what subtle breakages would happen when IPv6 requests come in.
Unless your product deals with the nitty gritty of the networking stack itself, pretty sure everything continues to hum along just fine, if the basics are covered.
pretty sure everything continues
to hum along just fine
Have you ever worked with a live system that grew for 10 years?
There could be tons of IP specific things in there. To enforce rate limits. For security. To do statistics. To do A/B tests...
So far, nobody said IPv4 will be turned off.
Maybe it will work for another 1000 years?
Railroads have been around for over 2000 years and are still going strong. Despite cars and planes.
Postal service has been going on for 4000 years. Since the times of the pharaohs! And It's still going strong, too. Despite phone, email and WhatsApp.
Rail is vastly superior to both planes and cars in many circumstances, if done right.
> Postal service has been going on for 4000 years. Since the times of the pharaohs! And It's still going strong, too.
With significant upgrades to both the transport and addressing layers :)
As a provider, the main benefit I've seen is that every user has a roughly unique IP. It's easier to audit things. It's really messy when lots of users are behind CGNat. Another benefit, eventually, is the cost of IPv4 space (but admittedly not a big problem now).
It's less likely that you will do so at a "customer" request, rather it will be ISP/Hosting provider that will start to charge you evermore increasing fees to rent your IP address. The the Ipv4 space gets more competitive you will see the fees for routable IPv4 address go up; and conveniently there will be "discounts" to go ipv6. That's when I imagine most businesses will make the switch.
How does this work?
In practice DNS64 is now being removed from a majority of networks because some specialty applications (I say "specialty" but these are work VPNs, conference systems and the like) reacts badly (because usually they can't understand IPv6 in the first place), replaced by either DS-Lite or plain dual-stack (possibly with CGNAT for IPv4).
Hetzner and other providers of this size already support hosting options for IPv6.
That said - my home ISP is not providing IPv6 at all, ISP we were getting office connection also provided no IPv6.