An anonymous reader writes "36 countries in the world have over 100% per-capita usage of mobile phones, and this is driving a real crunch on IPv4 addresses as more and more of these devices are data-capable. The mobile network operators are acting fast to deploy IPv6, and T-Mobile USA has had an IPv6-only trial going on for over 9 months now using NAT64 to bridge to IPv4 Internet content. It is interesting to note that the original plan for IPv6 transition, dual-stack, has failed since IPv4 addresses are effectively already exhausted for many people who want them. Dual-stack also causes many other issues and has forced the IETF to generate workarounds for end users called happy eyeballs (implying that eyeballs are not happy with dual-stack), and a big stink around DNS white-listing. How will you ensure that your network, users, and services continue to work in the address-fractured world of the future where some users have only IPv4 (AT&T ), some users have only IPv6 (mobile and machine-to-machine as well as developing countries), and other Internet nodes have both?"