In Windows 8, the company tries to address the varying scenarios that customers will face; if their infrastructure supports only IPv4, if it supports both IPv4 and IPv6; if it tries to connect with networks that have IPv4 or both IPv4 and IPv6 or just IPv6, according to a Building Windows 8 blog post.
The way Windows 8 support works, it tests for IPv6 connectivity when it first contacts another network that advertises its ability to route IPv6. If it works, Windows 8 will use it. Rather than relying on detecting a set of IPv6 addresses alone to make that decision, the software determines whether an IPv6 connection would improve or hurt the user experience. If the network has dual IPv4/IPv6 stacks, this will help improve the performance of applications using standard Windows APIs, the blog says.
The information gathered about IPv4 and IPv6 support in other networks is cached by Windows 8 and repeats the test every 30 days. If both are functioning, IPv6 gets preference.
A major goal in designing Windows 8 IPv6 features was to do no harm in existing corporate routing environments, says Christopher Palmer, a member of Microsoft's core networking management team who wrote the blog. To accomplish that, Windows 8 has two safeguards, he says:
"If the enterprise has provided specific routing information to a particular destination, then Windows 8 will honor that preference, regardless of the connectivity determined by Windows. In enterprise environments, Windows assumes that network administrators who configure such routes specifically thought it was a good idea to use those routes.