> The ultimate solution to IPv4 exhaustion is, of course, the complete transition of the Internet to IPv6, however, this will take time and until then there will be (by definition) networks and sites which only support IPv4.

Off-topic: I've always wondered why English speakers (or perhaps just Americans?) use "by definition" arguments so much (also just saying that things are by definition so and so).

People never seem to use "by definition" arguments and such in Finnish for example.

Definitions of mathematical objects aside, things in concept space are not eternal and can shift around. Is the usage a cultural thing? A quirk of language? Just some random trivial thing that just is and doesn't have any particular reason to it? :p