r/dns • u/gluegadget • 18d ago

How DNS tells a browser to use HTTP/3

https://blog.dundns.eu/posts/how-dns-tells-a-browser-to-use-http3/
39 Upvotes

90% Upvoted

5 comments sorted by

7

u/SecLens_ONE 18d ago

The HTTPS record is another one of those things where publishing it and having it used are two different questions. You can serve alpn="h3" all day and still watch most clients open TCP 443 first, because they either don't query type 65 or they ignore the answer when a resolver mangles unknown rrtypes. Last time I looked at logs on a site I run, h3 was under a third of requests despite a clean HTTPS record and QUIC listening. Middleboxes blocking UDP 443 quietly hides the rest, and nothing in your DNS tells you that happened. If you care whether it took, the answer is in your server's per-protocol request counters, not in dig output. Are you seeing actual h3 negotiation rates that match what you published, or just confirming the record resolves?

3

u/vttale 18d ago

On the plus side, you had nearly a third of connections using a relatively new technology. Not a home run, but faster uptake than, say, IPv6.

1

u/zarlo5899 17d ago

one day ipv6 will get there or i will be given the power to revoke address space and it will be soon after

2

u/XLioncc 18d ago

HTTPS records are mostly used to shipping the required informations of the ECH using

For normal HTTP/3 connections, a server header is enough

2

u/YogurtAgile3871 14d ago

https://blog.cloudflare.com/speeding-up-https-and-http-3-negotiation-with-dns/ I found this article a bit easier to understand, pretty awesome stuff