a new way of application designs IPv6 only applications, on top of a middleware that does IPv6-over-IPv4 IPv6 over IPv4 tunnel, Teredo or some other technology, could be p2p lower implementation costs/education once you educate guys with IPv6 you are ok increased transparency say goodbye to NAT traversal stuff in apps, lower layers will do it for you clients can communicate with each other directly (via IPv6) no need for triangular data path, central servers can become much smaller on IPv6-enabled environment there's no need for middleware/tunnelling much more efficient, lower delays/jitters example: rakuten messenger http://phone.rakuten.co.jp/