Save a round trip: optimizing for IETF's Happy Eyeballs v3

Connecting to a website used to be simple: resolve a name, open a connection. Not anymore. A browser now races IPv4 against IPv6, HTTP/3 against HTTP/2 and HTTP/1, and even DNS A and AAAA records against the newer HTTPS records. The number of address and protocol combinations keeps growing, and every browser behaves a little differently today. Happy Eyeballs v3, currently being standardized at the IETF, is about to change this.

For website operators the upcoming standard changes the economics of turning on new protocols. With it, the browser falls back to a working option faster and more safely. You can offer e.g. HTTP/3 and improve page load times without paying a connection-setup penalty when a path is broken or blocked. That makes it safe to experiment. I will show what Happy Eyeballs v3's performance impact looks like from the vantage point of millions of Firefox clients. Finally, you will learn how to optimize your own site with savearoundtrip.com, a small tool I built for exactly this.

Max Inden

Mozilla

Max is a software developer interested in networking, distributed systems and type theory. He works at Mozilla on Firefox's networking stack, focusing on HTTP3 and QUIC. Previously he was stewarding the peer-to-peer networking project libp2p, and before that the monitoring system Prometheus and its integration within the Kubernetes orchestrator. To find out more visit max-inden.de.