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HTTP/3: Use Cases, Envoy Support, and Google’s Rollout


With HTTP/3 being supported by 70%+ of browsers (including Chrome, Firefox, and Edge), and the official spec being finalized in June 2022, now is the time that organizations are beginning a widespread rollout of this protocol to gain performance and reliability. As leaders in the implementation of the HTTP/3 spec, Google and the Envoy Proxy teams have been working on rolling this out for quite some time, and they have learned many lessons.

Episode Guests

Alyssa Wilk
Senior Staff Software Engineer at Google
Alyssa Wilk, Senior Staff Software Engineer at Google, recently spoke with Daniel Bryant, Head of DevRel at Ambassador Labs. In a wide-ranging discussion that covered how HTTP/3 has been implemented over QUIC and UDP, the benefits and challenges offered by the new protocol, and the experience of Google publicly rolling out support for this protocol, a number of key themes emerged:

A number of key themes emerged:

  • HTTP/2 sped up HTTP/1 dramatically – but if you lose one packet on a connection, everything gets stalled until the packet is retransmitted.
  • This is a fundamental limitation of TCP, so HTTP/3 speeds up HTTP/2 even more by implementing the protocol on top of UDP.

  • The two big wins in HTTP/3 are the zero roundtrip handshake and improved congestion control. With the former, if you have already connected to the server previously you can bypass the three-way TCP handshake. With the latter, if you drop a packet, HTTP/3 will recover better and faster than HTTP/2.

  • Moreover, because HTTP/3 is implemented in user space, you get these performance benefits even if you haven’t updated (or can’t update) your operating system kernel.

  • Because there’s on average 2% packet loss on the Internet, HTTP/3 benefits virtually everyone.

  • End users who see even more benefit are those on lossier networks (e.g., emerging markets, mobile, IoT use cases) and those on old kernels (e.g., Windows users at large companies that don’t upgrade).

  • Adding HTTP/3 support to a proxy, ingress, or Edge Stack API gateway is non-trivial (unlike HTTP/2) as the protocol has very sophisticated congestion control and cryptography that needs to be implemented.

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