(第2空)A transport layer protocol has several responsibilities. One is to create a process-to-process (program-to-program) communication; TCP uses port( )to accomplish this. Another responsibility of a transport layer protocol is to create a( )and error-control mechanism at the transport level.TCP uses a sliding( )protocol to achieve flow control. It uses the acknowledgment packet, time-out, and retransmission to achieve( )control.The transport layer is also responsible for providing a connection mechanism for the application program. The application program sends( )of data to the transport layer.It is the responsibility of the transport layer at the sending station to make a connection with the receiver.