Cisco Blogs

Happy Eyeballs for World IPv6 Day

- June 7, 2011 - 11 Comments

Imagine how “happy” your eyeballs would become when you realize that your Internet connection failover time was drastically reduced from a full minute to less than half a second, Dan Wing and Andrew Yourtchenko of Cisco developed a methodology to do just that.

The Internet is changing. Network operators and content providers are beginning the widespread global deployment of IPv6, while keeping IPv4 up and running until IPv6 is ready to take over. Dan and Andrew have contributed to the cause of easing the adoption of IPv6 by documenting a methodology that will enable client applications to react more responsively in dual-stack failure scenarios by aggressively rectifying intermittent access issues and therefore preserve the end user experience for dual-stack IPv4 and IPv6 devices. This solution is documented in their IETF draft, cleverly named Happy Eyeballs. It is designed to keep the eyeballs of a computer end user “happy” in the face of problems that may exist when a host is attempting to establish IPv4 or IPv6 connectivity. The IETF draft document describes how client applications should behave when establishing IPv6 and IPv4 connectivity simultaneously, preferring IPv6 if the connectivity is successful, and disconnecting any remaining redundant (IPv4 / TCP) connections. By failing over quickly from IPv6 to IPv4, or from IPv4 to IPv6, the user is not affected by problems that occur in only one of the two IP versions in a dual-stack deployment. This can greatly reduce the connection times in problematic situations – from minutes to milliseconds, compared to the typical behavior in many implementations today.

In anticipation of World Ipv6 Day, Google Chrome has adopted a similar approach to what Dan and Andrew have documented, under the somewhat less light-hearted name “IPv4-Fallback”. This modification promises to ease potential trouble spots on World IPv6 Day, as well as future browser interactions with dual-stack network configurations. Google’s Internet browser, Chrome 11, uses a “hybrid” variation of Happy Eyeballs that is responsible for establishing, monitoring, and management of simultaneous parallel IP connections. This software enhancement produces significant results by reducing the fallback latency of a problematic IPv6 connection from between 20 and 75 seconds as is often seen today, to as little as 300 milliseconds.

Due to the positive results delivered to end-users, this sort of software modification will likely be added to other browsers, applications, and operating systems across the industry in the future. However, there is another side to the coin here in that connectivity issues are being masked and thereby may persist when they would otherwise result in a complaint and associated action by a network operator. This is the cost of IPv6 leaving the laboratory and entering the mainstream, the user experience for IPv6 is now paramount. Going forward, network operators will need to be proactive in their use of diagnostic tools to detect problems with IPv6 (or IPv4!) connectivity.

Production quality IPv6 is on the rise, and efficient coexistence with IPv4 is essential. As Joel Conover wrote in his blog, “Business Case for IPv6 – The Network Effect it is only through positive user experiences will the “Network Effect Jumpstart” occur. The more robust the network is, the more people will connect, and the more people who connect, the more robust network becomes. Happy Eyeballs is among the key innovations necessary to keep the Internet going and growing, fueling the next wave of growth fueled by IPv6.


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  1. what a revolution in the internet technology

  2. I almost like IPV6 and thanks for nice post.

  3. great revolution for internet users

  4. here starts the revolution in internet industry....nice post

  5. That is really great revolution for internet user...

  6. I like IPV6. Really love it.:)

  7. Roll on IPv6 it's been a slow, long, winding process.....

  8. Definitely a revolution. It seems like there are exciting times ahead - I only wonder how long it will take for us all to be using IPv6 rather than v4. I have a feeling it'll be a while. :(

  9. true, true... it really looks like a revolution :)

  10. It seems that there are a lot of security issues to be dealt with before the grand launching of iPV6. How safe will it be in the end?

  11. The revolution of internet !