I am curious about the usefulness of NAT and NAT traversal mechanisms once the deployment and usage of IPv6 increases. We have so many NAT traversal mechanisms (including proprietary) which are intended for mainly IPv4 devices/clients which are behind some kind of residential or enterprise NAT's. Given that NAT came about because of the lack of available addresses in IPv4, is it likely to become redundant once IPv6 is adopted widely in the coming years since IPv6 has enough addresses?
Of course, I do understand that adoption of IPv6 will not happen overnight and it is a gradual and painful process. And during this time, devices will have to support some sort of dual stack (IPv4 and IPv6) OR some network entity will do the translation between the two. I believe the firewalls will continue to exist to protect the end users and provide some security even in IPv6 world.
What is the attitude of IETF towards the NAT issue as far as standardization is concerned? given that they have ignored NAT all this while which thus led to broken protocols.
I hope someone can throw some light on this.
With IPv6, it will still be smart to avoid relying on IP addresses as host identifiers. Proposals to introduce standardized network prefix translators, e.g. I-D.mrw-nat66, never seem to be too far away from publication. More importantly, however, is that firewalls won't be going away anytime soon, c.f. I-D.ietf-v6ops-cpe-simple-security. While you may not have to worry about prefix or address translation breaking your applications, you can expect that ubiquitous firewalls will continue to interfere with application protocols and require you to do all the same basic traversal methods that IPv4/NAT entails in order to maintain state records in the middleboxes on your application paths.
来源：https://stackoverflow.com/questions/4647633/nat-traversal-and-ipv6