From RFC8483 [0] "Yeti DNS Testbed", which was published a few hours ago:<p>> Yeti DNS is an experimental, non-production root server testbed that provides an environment where technical and operational experiments can safely be performed without risk to production root server infrastructure.<p>In section 5 they publish experience with their IPv6-Only operation.<p>For example:<p>> There are reports of a notable packet drop rate due to the mistreatment of middleboxes on IPv6 fragments. One APNIC study reported that 37% of endpoints using IPv6-capable DNS resolvers cannot receive a fragmented IPv6 response over UDP.<p>Or:<p>> It was observed that Yeti-Root servers running Knot 2.0 would compress the zero-length label (the root domain, often represented as ".") using a pointer to an earlier example. Although legal, this encoding increases the encoded size of the root label from one octet to two; it was also found to break some client software -- in particular, the Go DNS library. Bug reports were filed against both Knot and the Go DNS library, and both were resolved in subsequent releases.<p>0: <a href="https://tools.ietf.org/html/rfc8483" rel="nofollow">https://tools.ietf.org/html/rfc8483</a>