I have no problem, yet, with IPv6 protocol per se. I think that we are unlucky being stuck with IPv4. However, the transition to IPv6 sucks big time. Clearly, two protocols (4 and 6) will run side by side for years and years. And then IPv4 will continue to run in data centers disguised as IPv6 for even more years. So you would imagine that transition is a pretty important subject. It is, and it has been under intensive research. Just take a look at IPv6 Wikipedia entry to see the number of references and RFCs. Unluckily, transition still sucks.
- NAT-PT. It was designated as a device/software that will translate from IPv4 to IPv6 and vice versa in a completely transparent way. In addition to architectural problems of NAT-PT there is a performance thing. It is slow. It slows down the traffic and does not make IPv6 looks good.
- Tunneling technologies. There are few of those: ISATAP, 6to4 and Teredo. There is inherit problem with all tunnels: they waste bandwidth. They make IPv6 "feel" slower than IPv4, which reduces the drive to move to the new technology.
- End-to-end IPSec. IPv6 hosts must support IPSec. The problem is that end-to-end authentication cannot work with NAT-PT. This means that there are severe limitations on topology. If IPv6 host wants to talk to IPv4 host with end-to-end IPSec, the traffic cannot pass NAT-PT. What if you do pass NAT-PT and you have to work with IPSec, after all it is a must for IPv6, then what do you do? You fall back to IPv4.
The world will move to IPv6 in time, South Korea and Japan are good examples. However, it does sucks that the transition itself is puts potential customers from the protocol.
This post is short. I am still getting on track with this blog thing.