China Telecom China Telecom With the approaching exhaustion of IPv4 address space, large-scale ISPs are now facing the option to deploy IPv6 in a timely manner. However, most existing IPv6 transition solutions have tradeoff between scalability and efficiency. This draft proposes a lightweight address family transition mechanism named LAFT6. It only needs to maintain per-subscriber state entries in core network and there is no specific address format requirement for users' IPv6 address. It is a lightweight solution in terms of state-management, addressing and routing. The experimental results have shown that LAFT6 is scalable and can be rapidly deployed in commercial ISP network.