Lazy Eye Inspection: Capturing the State of Happy Eyeballs Implementations

During the transitioning to an IPv6-only communication, many devices and networks settled on a dual-stack setup.
IPv4 and IPv6 are available to these hosts for new connections.
Happy Eyeballs (HE) describes a mechanism to prefer IPv6 for such hosts while ensuring a fast fallback to IPv4 when IPv6 fails.
The IETF is currently working on the third version of HE which includes more connection setup parameters (e.g., ALPN).
While the standards include recommendations for HE parameter choices, it is up to the client and OS to implement HE.
This talk presents the state of HE in various clients, particularly web browsers.
Measuring and evaluating these properties help to find and understand IPv6 deployment hurdles.

We introduced a framework to analyze and measure clients’ HE implementations and parameter choices.
Additionally, we implemented a web-based measurement tool.
This tool is publicly available to the community (https://www.happy-eyeballs.net) and measures the browser’s HE behavior.

According to our evaluation, only Safari supports all HE v1 and v2 features.
Safari is also the only client implementation in our study that uses a dynamic IPv4 connection attempt delay, a resolution delay, and interlaces addresses.
We further show that problems with the DNS A record lookup can even delay and interrupt the network connectivity despite a fully functional IPv6 setup with Chrome and Firefox.
All major browser engine developer teams claim to work on implementing the HEv3 draft.
We are currently extending our measuring tool to support HEv3 measurements.
Our tool and evaluation is not only useful for browser vendors but also to network operators and content providers.
The results can help to understand and identify user complains related to IPv4/IPv6 connectivity.