Re:DNS over HTTPS–What Is It and Why Do People Care? [pdf]
by bluejekyll on Monday October 21, 2019 @01:46AM
(#21309616)
HTTP2 isn't significantly more overhead than TLS in my experience.
Also, using DoT over 443 would mean that you have an issue with traffic not being distinguishable for routing purposes at the edge. By making DNS on 443 DoH, it means that all HTTP2 routers/loadbalancers/etc. can work the same regardless of it being a Web request or a DNS request, because then they are both Web, i.e. HTTP, requests.
Also, using DoT over 443 would mean that you have an issue with traffic not being distinguishable for routing purposes at the edge. By making DNS on 443 DoH, it means that all HTTP2 routers/loadbalancers/etc. can work the same regardless of it being a Web request or a DNS request, because then they are both Web, i.e. HTTP, requests.