What kind of (server) infrastructure is necessary for automatic IPv6 tunneling to work? How would a client automatically find an endpoint?

I'm not even sure if this is a standard feature of IPv6 or not, but setting up an IPv6 tunnel using an Apple Airport base station I noticed that it offers IPv6 tunneling with automatic configuration. Trying it, it didn't work (i.e. it failed to establish a tunnel). I'd imagine the ISP would need to run some sort of server advertising where an endpoint can be found? How is this supposed to work exactly?