> However, you can also advertise H3 support via Alt-Svc, so presumably you could do the same with TurboTLS.
Alt-Svc is an http header, by the time you get http you already have TLS setup. In a Alt-Svc workflow you generally advertise h2 in TLS ALPN, then use Alt-Svc to advertise h3 capability in the headers of the first response, and then the client establishes a h3 connection and closes the h2 connection when it is ready (and the h2 connection does not have any queued requests). At least that is my understanding.
Yes, that's correct. Basically the only good way to have a "first contact" fast track setup like this is by priming in DNS. My point is that the situation is th same for TurboTLS and QUIC/H3 in this respect.
I just meant that QUIC/H3 is beneficial even after you already have a connection, so upgrading an existing connection is a valid strategy. TurboTLS is only beneficial for establishing the connection, so it needs to have prior knowledge about the support to be useful at all.
Alt-Svc is an http header, by the time you get http you already have TLS setup. In a Alt-Svc workflow you generally advertise h2 in TLS ALPN, then use Alt-Svc to advertise h3 capability in the headers of the first response, and then the client establishes a h3 connection and closes the h2 connection when it is ready (and the h2 connection does not have any queued requests). At least that is my understanding.