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.
Yes, there could be. But in the end, those are just parameters of the specific networks/services that make up the internet.
Considering that routing is not deterministic, you could get vastly different characteristics from point A to point B across the internet at specific times anyways.
No - but I think at some point, you or your customers will see benefits in IPv6, or your clients may require it by policy (some of mine do). No rush, just saying, it takes time, may as well start with bits and pieces now.
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.
It unfortunately involves CGNATted IPv4, but it's either DS-Lite (https://datatracker.ietf.org/doc/html/rfc6333) where the end-user router emulates a dual-stack network but encapsulates IPv4 traffic on IPv6 from the perimeter to the CGNAT device at the ISP or just plain NAT64/DNS64 (https://datatracker.ietf.org/doc/html/rfc6147) where IPv4 traffic is relayed at dedicated IPv6 addresses operated by the ISP with the help of special DNS (which might be the GP meant for IPv6-only networks, but it tends to be unreliable for a lot of reasons).
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).
I forget this part of IPv6 class (I've literally gone to several IPv6 classes throughout the years but then end up forgetting details because I've yet to use it in production), but since the IPv6 space is so large, it's trivial to put an IPv4 address into it, and so they make NAT 6to4 type gateways that map the IPv4 internet into a block on the IPv6 network.
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.