Apple Inc. Apple Inc. "Happy Eyeballs" (RFC6555) is the name for a technique of reducing user-visible delays on dual-stack hosts. Since one address family (IPv4 or IPv6) may be blocked, broken, or sub-optimal on a network, clients that attempt connections for both address families in parallel have a higher chance of establishing a connection sooner. Now that this approach has been deployed at scale and measured for several years, the algorithm specification can be refined to improve its reliability and generalization.