Deploying IPv6-only network

Happens only in far future, or when admins got tired of maintaining IPv4

IPv6-only node needs to be able to talk with IPv4-only node
Need to click www.yahoo.com...

Translator
Appilication layer: web proxy, fwtk, sendmail
TCP layer: socks, fwtk
IP layer: header translation

Has the same problems with NAT (not end-to-end, single point of failure)