A transport layer protocol has several responsibilities, One is to create a process-to-process (program-to-program) communication; TCP uses port (1) to accomplish this. Another responsibility of a transport layer protocol is to create a (2) and error-control mechanism at the transport level. TCP uses a sliding (3) protocol to achieve flow control. It uses the acknowledgment packet, time-out, and retransmission to achieve (4) control. The transport layer is also responsible for providing a connection mechanism for the application program. The application program sends (5) 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.空白(4)处应选择()
A. packet
B. time
C. error
D. phase
Both bus and tree topologies are characterized by the use of multipoint (1).For the bus, all stations attach, through appropriate hardware (2) known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3). A transmission from any station propagates the length of the medium in both directions and can be received by all other (4). At each end of the bus is a (5) , which absorbs any signal, removing it from the bus.空白(1)处应选择()
A. medium
B. connection
C. token
D. resource