Windows Network Stack Diagram

Internet Protocol version 6 (IPv6) is not a superset of IPv4, but installs and runs side-by-side with it. Both communicate with the various data link layer protocols (second layer from the bottom) specific to the type of physical media to which the device is connected (bottom layer), yet each has a different protocol for mapping IP addresses to the hardware addresses of other devices on the network. Both versions of IP also support Internet Control Message Protocol (ICMP), which provides basic control and diagnostic functions, such as responding to a ping request to prove the device is reachable.

Above both sits the transport layer responsible for end-to-end connectivity, consisting of the Transmission Control Protocol (TCP) for reliable, connection-oriented traffic and Universal Datagram Protocol (UDP) for connectionless traffic in which checking for reliable delivery is the responsibility of a higher-layer protocol. While not required by the Internet Engineering Task Force (IETF) standard, Microsoft has chosen to use two separate TCP and UDP stacks, one set connected to IPv4 and the other to IPv6. Other OS and router vendors use a single TCP protocol and single UDP protocol, each of which connects to both IPv4 and IPv6.