Socket options at the SOL_SOCKET and IPPROTO_TCP levels are not dependent on the IP layer being used. They are supported for both AF_INET and AF_INET6 sockets.

Socket options at the IPPROTO_IP level support IPv4. They are not supported on AF_INET6 sockets.

Not all socket options at these levels are supported by all APIs. See API-specific information for specific socket options for support levels.