bert64

How you represent the address is arbitrary, using a colon instead of a dot matters little as underneath it's just an integer with the only difference being 32 or 128bit.

Using a dot causes its own problems, because it conflicts with DNS. DNS allows fully numeric domain names, but they conflict with legacy ip so are not used on a the public DNS. Using hex would make the problem worse as it's perfectly valid to have an ipv6 address ending "de" for example, which is the TLD for germany.

Legacy addresses can be represented via hex too - try ping 0xdeadbeef.

The socket apis between v6 and legacy ip are largely as compatible as they can be, you need to use sockaddr_in6 and AF_INET6 which is the same as you propose. You can open an AF_INET6 socket and still connect to legacy addresses with it.

For higher level languages that don't deal with fixed size memory structures directly it's pretty much fully compatible, you can just say "connect www.google.com tcp/443" or equivalent, and the system takes care of resolving what protocol and address to connect to.

Depends on the phone and carrier, if i enable tethering (iphone 8) then my connected devices get IPv6 addresses. Some android tethering implementations use CLAT and only give you legacy IP. Some old routers might do the same, or might do so by default until you reconfigure them.

Here at least the mobile network uses cgnat for ipv4, but fully routable ipv6 - so the only way i can get inbound connections over the mobile network is to use ipv6.

According to linkedin it varies and is up to 40% in some cases they measured:

https://www.linkedin.com/pulse/ipv6-measurements-zaid-ali-ka...

A fast NAT gateway which is lightly loaded might make little difference, a heavily loaded one can make a big difference.

Google stats also show slight latency improvements for IPv6: https://www.google.com/intl/en/ipv6/statistics.html#tab=per-...

Of course these are generalised stats, there will be some users with tunnels which will impair IPv6 performance, while other users might be behind multiple layers of NAT.