Internet Engineering Task Force (IETF) D. Wing Request for Comments: 6555 A. Yourtchenko Category: Standards Track Cisco ISSN: 2070-1721 April 2012 Happy Eyeballs: Success with Dual-Stack Hosts Abstract When a server's IPv4 path and protocol are working, but the server's IPv6 path and protocol are not working, a dual-stack client application experiences significant connection delay compared to an