On Oct 1, 2015, at 3:42 PM, Todd Underwood <toddunder@gmail.com> wrote:
it's just a new addressing protocol that happens to not work with the rest of the internet. it's unfortunate that we made that mistake
I understand the comment, but I see some issues with it. The problem isn't that IPv6 isn't backward-compatible, or that the changes to the Socket Library aren't backward compatible (the socket interface being the reason we have to upgrade applications, and btw getaddrinfo *is* backward-compatible), it's that the old stuff (IPv4, gethostbyname) aren't forward compatible. If we had deployed a new protocol that allowed us to use IPv4 addresses as well as the new format (which, BTW, we did), it would still be a new protocol that had to be deployed and enabled. There's no way to change the IPv4 address to be larger, or to get gethostbyname to return a non-IPv4 address. Had there been an easy way to expand an IPv4 address to a larger number of bytes, we wouldn't have needed to replace IPv4.