[noway421]

Wondering the same- how’s the compatibility with very restrictive networks? Say a university/corporate network that only allows port 443 and DPI’d 80 egress. QUIC won’t pass through that since it’s UDP. Can server and client reliably negotiate a fallback to http/2 in such a case?

[supriyo-biswas]

Yes. Browsers typically initiate a TLS (TCP) connection to port 443 for HTTP1/2, and then upgrade to HTTP/3 based on the Alt-Svc header.

[fridek]

This. There are also clients that with a little config will let cache the support level per-host, and even provide a list of hosts that the initial request should race TCP and QUIC to.

https://developer.android.com/guide/topics/connectivity/cron...

[noway421]

What if your browser receives Alt-Svc header and switches to http/3 on one network (say mobile data), but then you switch to a restrictive WiFi that has UDP disabled. All without restarting your browser/within one "session" of your http client. Wouldn't you start having connectivity issues that would be hard to troubleshoot? In that scenario, having http3 disabled is beneficial.

[oefrha]

HTTP/1.1 isn’t going anywhere in any popular server, so yeah, HTTP/2 fallback isn’t a problem. (HTTP/1.1 is basically required even if you just want to serve an https redirect on port 80, since h2 requires TLS. The clear text h2c protocol has no adoption AFAICT.)

[ignoramous]

Yep, just like IPv4 didn't, HTTP/1 and H2 aren't going anywhere anytime soon.

[Ekaros]

HTTP2 is probably first one to go or be replaced. You can live without it or update it to whatever next thing.

[j16sdiz]

nit: It is HTTP/1.1 . HTTP/1.0 have long gone

[wraptile]

IPv4 is not going away because it's valuable (as in limited supply creates a market). HTTP 1.1 is already unusuable in modern web as you'll be instantly blocked by cloudflare and gang. HTTP2 is likely to follow in near future as replacing it will be much easier than replacing http1.1.