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Without taking a position on TurboTLS versus H3... There are actually two types of middlebox problems: 1. DNS resolvers which don't carry new record types. 2.

Without taking a position on TurboTLS versus H3... There are actually two types of middlebox problems: 1. DNS resolvers which don't carry new record types. 2. Middleboxes which don't properly handle UDP-based protocols (2) applies to both H3 and to TurboTLS, and in both cases you need some kind of fallback in case things fail. (2) applies to TurboTLS as specified. However, it's worth noting that H3 also has a DNS-based mechanism for advertising support via the HTTPS record (that is also used for ECH). However, you can also advertise H3 support via Alt-Svc, so presumably you could do the same with TurboTLS. In general, any new transport like H3 or TurboTLS has to be offered on a best-effort basis with a fallback, otherwise you'll have a lot of hard failures.

londons_explore 4y ago
And H3 is already pretty widely deployed, so unless TurboTLS has some really compelling benefits, it will lose by default. HTTP/3 is in most browsers under 3 years old, and most server stacks support it (usually with a bit of extra config).
SahAssar 4y ago
> 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.
- ekr____ 4y ago
  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.
  - SahAssar 4y ago
    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.

londons_explore 4y ago

And H3 is already pretty widely deployed, so unless TurboTLS has some really compelling benefits, it will lose by default. HTTP/3 is in most browsers under 3 years old, and most server stacks support it (usually with a bit of extra config).

SahAssar 4y ago

> 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.

ekr____ 4y ago
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.
- SahAssar 4y ago
  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.