Some operating systems, such as Linux and H-UX, implement a half-duplex close sequence in the TCP stack. If the host actively closes a connection, while still having unread incoming data available, the host sends the signal RST (losing any received data) instead of FIN. This assures a TCP application that the remote process has read all the transmitted data by waiting for the signal FIN, before it actively closes the connection. The remote process cannot distinguish between an RST signal for "connection aborting" and "data loss". Both cause the remote stack to lose all data received.