Comment by bigcityslider

V5 would depend on IPv6 packet parsing to work, but the reason some are avoiding v6 now is really everything else about it, which v5 avoids.

Agree about the rest. Also I did have a note about 6to4 in there but had to remove it due to char limit. RFC 6343 has some retrospective on why it got abandoned, basically the config-free option (anycast) was too flaky.