There are currently three operative technologies for trafficking packets in IPv6. The main question here is, how to developed system that can be used on IPv4 and IPv6 applications on existing machines? This means that for example if you have server running on IPv6 that can communicate with IPv4 clients or vice versa. This might sound like a simple problem to solve, but complexity is much bigger. You can solve that kind of problem with additional hardware upgrades or software solutions – however this solutions and development doesn’t come cheap and it takes some time to put it in production.
In White paper: NAT64 Technology: Connecting IPv6 and IPv4 networks of Cisco there are mentions three types of solutions:
Dual Stack Network
In this type of network IPv4 and IPv6 operate in tandem over shred or dedicated links, it’s deployed across infrastructure, so that configuration and routing protocols handle both IPv4 and IPv6 addressing and adjacencies. However this solution requires many hardware and software upgrades, because IPv6 needs to be active on all network elements, but after the upgrade this kind of solution will require less maintenance changes in the future.
This method is ad-hoc solution, it works like this: it works as overlay network that tunnels one protocol over the other by encapsulating IPv6 packets within IPv4 packets and IPv4 packets within IPv6 packets – not the safest solution. This solution does not disturb old protocols and provides connectivity with the new protocol. There are two disadvantages mentioned in RFC 6144 – users of the new architecture cannot use the services of underlying infrastructure, so tunneling doesn’t solve this problem, however you can incorporate dual-stack host, and make interoperability with users on the old protocol.
My favourite kind of method, because it’s kind of raw, but it works. Translation method or AFT Address Family Translation it facilitates communication between IPv6-only and IPv4-only hosts and networks (transit, access or edge network) by performing IP header and address translation between the two address families. However is not ment to be a long-term support strategy.
Implementing IPv6 is a major problem for business subscribers and enterprises, because of the critical applications and servers that require 24/7 uptime and for the time of transit and migration, business continuity would be hard to maintain.