IPv6 is short for "Internet Protocol Version 6". IPv6 is the "next generation" protocol designed by the IETF to replace the current version Internet Protocol, IP Version 4 ("IPv4").
Most of today's internet uses IPv4, which is now nearly twenty years old. IPv4 has been remarkably resilient in spite of its age, but it is beginning to have problems. Most importantly, there is a growing shortage of IPv4 addresses, which are needed by all new machines added to the Internet.
IPv6 fixes a number of problems in IPv4, such as the limited number of available IPv4 addresses. It also adds many improvements to IPv4 in areas such as routing and network autoconfiguration. IPv6 is expected to gradually replace IPv4, with the two coexisting for a number of years during a transition period.
Windows IPv6 Implementation
Microsoft Windows XP includes an IPv6 implementation intended for development use and trial network deployments. Installation instructions and other information regarding using IPv6 in Windows XP can be found in the IPv6 for Windows XP FAQ.
Earlier versions of Windows did not ship with a built-in IPv6 implementation. Microsoft has an add-on IPv6 implementation for Windows 2000 available for developer use. Please see their web site at http://msdn.microsoft.com/downloads/sdks/platform/tpipv6.asp
Microsoft Research has an add-on IPv6 implementation for Windows 2000 and NT 4 available. Please see their web site at http://www.research.microsoft.com/msripv6/ for more information and to download the release.
Trumpet also now has an IPv6 Winsock implementation available for Windows. Please see the web site at http://www.trumpet.com.au/ipv6.htm
For more information visit : http://www.ipv6.org/ regarding ipv6 implementations, specifications, enabled appliactions & all other sources.
source : http://www.ipv6.org/