1. DNS/Bert
https://ds9a.nl/tmp/powerdns-xs4all-presentatie.pdf
2. dns-operations 2018
[dns-operations] Spoofing DNS with fragments
https://lists.dns-oarc.net/pipermail/dns-operations/2018-September/017949.html
https://lists.dns-oarc.net/pipermail/dns-operations/2018-September/017950.html
This is mostly a solved problem from the point of view of the low-level infrastructure: Current Linux has mitigations DNS servers can use to avoid fragmented responses for reasonable response buffer sizes (such as 1200 bytes) even when ICMP path MTU poisoning is used.
By the way, I'm not sure if DNSSEC mitigates the denial-of-service aspect of this vulnerability. If this attack is simple enough to carry out, people will use it to install bad glue for DNSSEC-secured domains, blocking successful resolution, just for fun. There is no alternative to lowering the buffer size *and* avoiding fragmentation.