The relationship is that DNS is acting as an index service
for IPv6 addresses. In doing so it treats them as simple
hierarchical addresses, i.e. like fat IPv4 addresses.
The question as to whether that is the correct handling of
IPv6 addresses is a valid one. This thread started with
exactly such a question being raised, but the rationale on
how DNS *could* be optimized for IPV6 was not spelled out.
There is no IPv6 service that guarantees that the identifiers are
actually world-wide unique. In fact, there is ample evidence that they
often will not be. Poorly configured interface cards are known to have
phony IEEE-802 addresses; privacy addresses are random numbers that are
only statistically unique; configured addresses may use user assigned
values. In all these cases, local collisions can be detected, global
collisions cannot be.
There is also no requirement that a given multi-homed hosts combines the
same identifier with different prefixes. Privacy advocates will no doubt
argue that a multi-homed host should associate different identifiers
with different provider prefixes, so it cannot be tracked by
big-brother.
-- Christian Huitema