> There is a difficulty in that it does behave quite differently to IPv4

Which can be fine if you have a /solid/ transition plan to move networks wholesale from v4 to v6. They absolutely failed on this point and almost purposefully refused to carry over any familiar mechanisms to make dual stack easier to manage.

It's a University protocol that escaped into commercial usage based mostly on false fears of global routing table size becoming unmanageable or impossible to store in RAM. The results are absolutely predictable.