I first heard about IPv6 many years ago in the times when IP Addresses as we know them (IPv4) were thought to be nearly at a running out stage. Then, largely due to new routing protocols and the availability of large numbers of unused Class A based subnets the crisis was averted for the time being.

Because of the aversion of the postponment of the IPv4 run-out, take up of
IPv6 had been slow to gain momentum. However, Chinese authorities have just
announced the launch of "CERNET2" which is 100% IPv6 and which they
claim is the World’’s largest IPv6 network. CERNET2 will form the backbone of
their Internet Infrastructure. Apparrently a trial on CERNET2 between Beijing
and Tianjin on December 7 achieved a speed of 40 gigabits per second, claimed to be the highest in the world in real applications.

More details can be found on this site.

You can find full details on IP Version 6 or IPv6, here.