January 15, 2014 archive
If an application gets back both an IPv4 and IPv6 address from DNS, which one should the application use to connect? This dilemma for a “dual-stack” host is one that Dan Wing and Andrew Yourtchenko addressed in RFC 6555, “Happy Eyeballs: Success with Dual-Stack Hosts“ that can be found at:
At a high level, the premise is quite simple: open up a connection over BOTH IPv4 and IPv6 and use whichever one is fastest.
The idea being that the user will experience the best possible speed and will therefore have “happy eyeballs” if they are using something like a web browser where visual content is being viewed. RFC 6555 offers a number of suggestions and offers ideas for application developers to consider.
A variation of “happy eyeballs” is now implemented in most major web browsers, but the idea is not just for web browsers. Basically any application operating on a dual stack computer can use this idea to make the user experience as fast as possible.