Looking at implementing an internal IPv6 network in parallel with the existing IPv4 network on RFC1918 addresses.
At first glance it looks nice and simple. IPv6 has its equivalent of RFC1918 addresses -- with even better semantics. It has 'site scope' addresses, and machines can be given _both_ 'site' and 'global' scope addresses, and basically do the right thing in all circumstances... using the internal addresses for internal communication, and the external addresses for everything else.
So each site on the intranet can have its own _global_ IPv6 link, with optimal routing out the local connection to the Real World, while tunnelling the site-scope addresses over the CIPE links with the RFC1918 IPv4 traffic. None of this NAT-from-internal-to-public-addresses crap which we have for IPv4.
Unfortunately it seems that the concept of site scope is to be abolished. Discussion of the various possible alternative implementation plans has failed to turn up any possibilities which are even _close_ to being as simple and effective.
I wonder if the martians are to blame. They know that TCPv4 isn't good enough for us to communicate with our Martian-invasion fleet, and they're determined to scupper our IPv6 deployment efforts by fucking it up for us... so they placed mind-control anal probes into the IPv6 WG and made them abolish the part which was going to actually let people deploy IPv6 sanely in large organisations.
Or maybe not. Perhaps there are just telcos involved?