Dual IP layer architecture for IPv6
The implementation of IPv6 in Windows XP and Windows Server 2003 is a dual stack architecture. For IPv6 support, you have to install a separate protocol through the Network Connections folder. The separate IPv6 protocol stack had its own Transport layer that included Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) and its own Framing layer. Changes to protocols in either the Transport or Framing layers had to be done to two Windows drivers; Tcpip.sys for the IPv4 protocol stack and Tcpip6.sys for the IPv6 protocol stack.
The Next Generation TCP/IP stack supports the dual IP layer architecture in which the IPv4 and IPv6 implementations share common Transport and Framing layers. The Next Generation TCP/IP stack has both IPv4 and IPv6 enabled by default. There is no need to install a separate component to obtain IPv6 support.
This is good news for ISV’s preparing to satisfy government requirements, but, of course, there is more to IPv6 support than just the stack.