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by niftich 3539 days ago
This is mostly correct but not entirely.

HTTPS is layered such that it's HTTP > TLS > TCP.

QUIC replaces the 'TLS > TCP' portion with 'QUIC > UDP', which you can then run HTTP or HTTP2 on top of.

QUIC is not an alternative to HTTP2 (yet), although there's work underway to (re-)define HTTP2 in terms of QUIC [1], thereby replacing the awkward transport protocol aspects of HTTP2 with the very similar mechanisms provided by QUIC.

[1] https://tools.ietf.org/html/draft-shade-quic-http2-mapping-0...
3 comments
pliu 3539 days ago
Thanks for the clarification, I guess I was confused about how it worked.

For those seeking more detail, I found these two links helpful:

https://docs.google.com/presentation/d/15e1bLKYeN56GL1oTJSF9...

https://ma.ttias.be/googles-quic-protocol-moving-web-tcp-udp...

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Matthias247 3539 days ago
The not-so-nice part about the newer HTTP versions is that they are not really layered in the classical sense. This means HTTP/1, HTTP/2 and HTTP over QUIC all carry the same semantics (you got methods, addresses, headers, and body streams), but implementation of HTTP itself is different and it's not only a substitution of the underlying transport layer: E.g. in HTTP/2 there's no classical HTTP data transferred over a multiplexed stream (like what HTTP over SCTP could have brought us). Instead it carries HTTP aspects (headers), multiplexing and flow control all in a single layer which makes layering and generic reuse hard.

Have not looked into that QUIC mapping yet, but I have read that generic use is a goal for it, which is good. If HTTP over QUIC succeeds (it probably will if pushed by google) I'm wondering how of how much use HTTP/2 still will be. Classical HTTP will most likely always exist as it's easy to implement and is covered by lots of systems (even embedded) and libraries.

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jimktrains2 3539 days ago
Is QUIC specific to HTTP, or can it be used as as transport mechanism for arbitrary protocols?
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niftich 3539 days ago
QUIC stands on its own; it just so happens that QUIC and SPDY (the predecessor of HTTP/2) show some convergent evolution.

You could use QUIC to transport other L7 protocols, but tracking down generic-enough implementations may be difficult, or at least was the case in the past [1][2]. Maybe things are better now [3].

[1] https://daniel.haxx.se/blog/2016/07/20/curl-wants-to-quic/

[2] http://stackoverflow.com/questions/17896432/

[3] https://github.com/google/proto-quic

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