T-Mobile USA has launched an IPv6 web site -- http://ipv6.t-mobile.com/. Only the front page (including images and CSS) is reachable over IPv6; most of the links are broken or redirect to the IPv4-only site. Clearly, it's still a work-in-progress. This appears to be a futher development in their IPv6 strategy announced at Google's IPv6 Implementors Conference few weeks ago. (Btw, the conference was quite good; hats off to Erik, Lorenzo, and the rest of the Google team.)

T-Mobile USA makes heavy use of NAT44 and bogon addresses. Going forward, this isn't sustainable. So they've decided that future cellular deployments will be IPv6-only, with NAT64 to access the "legacy" IPv4 Internet (slides | video). Yes, NAT is bad, but this approach is the least-bad of the alternatives. There's still only one layer of NAT, it gets IPv6 on a large number of end nodes, and IPv6-enabled content (Google, Netflix, Facebook, etc) isn't NAT'ed at all. Over time, less traffic should flow through the NAT64 boxes as more content is IPv6-enabled. T-Mobile USA suspects they can run 50% of their cellular data traffic over IPv6 by the end of 2011 (apparently they send a lot of traffic to Google and Facebook).

On a personal note, it was very entertaining to hear Cameron Byrne from T-Mobile USA repeatedly tell content providers, "Our users are going to access your content over IPv6. The only relevant question is 'will we make the AAAA record or will you?' Wouldn't you rather be the one to do it so you have control?" After the fourth or fifth time it sunk in: These folks are serious.

This is an even gutsier move than Verizon. VZ is dual-stacking their LTE network and mandating IPv6 support on all devices. Let's hope T-Mobile is really good at running large-scale NATs.