[contravariant]

Right, all this kind of feels as if HTTP/2 is trying to solve transport layer problems in the application layer. Especially if you leave out the server initiated push. I can't really pretend to know much about this but I can't say I'm surprised that this causes problems when the underlying transport-layer protocol is trying to solve the same problem.

So is it correct to view HTTP/3 as basically taking a step back and just running HTTP over a different transport-layer protocol (QUIC)? (If so I think the name is a bit confusing, HTTP over QUIC would be much clearer)

[cwp]

That's true, but the transport layer has ossified, and the application layer is the only place we can still innovate. RIP SCTP.

[contravariant]

Still sad, it would have been much nicer to just keep HTTP as is and just put in a different transport layer. Or maybe extend HTTP a little but right now we've got a protocol independent HTTP/1.1 and a new HTTP/3 which rather than being more general strictly relies on a single protocol.

[nbm]

In some ways, HTTP 3 is the same HTTP messages, just over QUIC.

But as you get into other features, there are differences. And your clients and servers need to both have fallbacks to HTTP 2, since UDP connectivity might not be available, and fallback is expected.

So, you have to build support for having working push, or not. Or having working priorities, or not. Or having long-lived non-HTTP sockets, or using fallbacks like web sockets or even long polling. There’s even more fun on the horizon, and I’m not looking forward to my colleagues thinking of a fallback strategy for some of those...

[mumblemumble]

It was originally called HTTP over QUIC, and got renamed to HTTP/3 in order to avoid some other confusion.

https://en.wikipedia.org/wiki/HTTP/3#History

[SahAssar]

HTTP/2 is what you do if you're confined to using TCP. HTTP/3 is what you get if you use UDP to solve the same problems (and new problems discovered by trying it over TCP).