I'm curious about how practical UDP amplification/reflection attacks will be in the wild with QUIC. A cloudflare blog mentions it in passing ( https://blog.cloudflare.com/head-start-with-quic/ ). I haven't dug into the protocol, but since what replaces the TCP SYN/ACK is now also setting up encryption, a lot more data is flying back and forth.

Putting HTTP/3 on a userspace QUIC stack solves a number of these problems.