RFC 6724

[Phillip Hellewell]

Here are the policy tables for comparison:

RFC 3484:
      Prefix        Precedence Label
      ::1/128               50     0
      ::/0                  40     1
      2002::/16             30     2
      ::/96                 20     3
      ::ffff:0:0/96         10     4

RFC 6724:
      Prefix        Precedence Label
      ::1/128               50     0
      ::/0                  40     1
      ::ffff:0:0/96         35     4
      2002::/16             30     2
      2001::/32              5     5
      fc00::/7               3    13
      ::/96                  1     3
      fec0::/10              1    11
      3ffe::/16              1    12

In general, what you are seeing is a depreference for
old/obsolete/unreliable ipv6 prefixes such as Teredo, site-local,
6to4, 6bone, etc.

The changes look good and make sense to me, except for one minor tweak
I would suggest.  The rule for fc00::/7 was added so that global IPv6
would be preferred over ULAs.  That makes sense, but as you can see it
has also been placed below IPv4 (::ffff:0:0/96).  This also makes
sense if we are talking about a global IPv4 being preferred over a
(local) ULA IPv6.  However, if choosing between a private IPv4 (10/8,
172.16/12, 192.168/16) or a ULA IPv6, they have the same scope so the
IPv6 address ought to be preferred.  To solve this, I would add in
three rules for the private IPv4 prefixes with a precedence of 2, so
that ULA will be preferred over them.

Phillip