Hacker News Reader

With 'normal' DNS, UDP with the default and TCP is used if the packet size becomes too large. There are other TCP-only variants such as DoT (DNS over TLS) and DoH (DNS over HTTPS).

I don't think the performance would matter much with some basic caching (or even just OS-level caching), but there is limited memory in an ESP so maybe that is it. I have never noticed issues with DoT and DoH which are theoretically much heavier protocols.

That’s odd because DNS is the quintessential UDP-based protocol. “From the time of its origin in 1983 the DNS has used the User Datagram Protocol (UDP) for transport over IP.”. DNS over TCP was only introduced as a later addition (admittedly, in 1989).

> I always thought it was TCP only!

So did the NIH firewall administrator:

https://news.ycombinator.com/item?id=43229201

Huh, I didn't know it had a TCP option, I thought it was UDP-only.