My best guess is that the
interesting ipv6 icmp traffic I mentioned before is part of the
efforts of Akamai to build a 'performance map' of the IPv6 Internet, as
mentioned in
Akamai: Why our IPv6 upgrade is harder than Google's - Network World.
What we do in our mapping infrastructure is to build a performance map
of the Internet. A lot of what we do for our content provider customers
is provide superior performance by providing route optimization across
the fabric of the 12,000 service providers that are the Internet.
So my old IPv6 nameserver address is part of this mapping effort. This
traffic would stay under the radar if it wasn't the only traffic left on
my old IPv6 tunnel link.
My guess is based on the pattern in the addresses, and all whois records
which give a detailed enough answer show Akamai.