Consider a full-duplex point-to-point link that connects two nodes. The transmission time for a frame is 1 second and the round trip time is 4 seconds. That is, if a node begins to transmit a frame at time t=0, it will receive the acknowledgment a t=4 seconds. The source node starts to transmit frames at time 0, and it has a total of 8 frames to send. For all parts of this problem assume that, due to errors on the channel, the transmission of the first frame is not received correctly, but that all other transmissions are successful. Define the transfer time as the time until the source nodes have determined that the destination node has successfully received all frames. The source sets a timer for each outstanding frame and if an acknowledgment is not received in 4 seconds the frame is retransmitted

(a) What is the transfer time for the stop-and-wait protocol?

(b) What is the transfer time if the sliding window protocol is used and both the senders and receivers window sizes are 4? (c) What is the transfer time if the go-back-N protocol is used and the senders window size is 4 and the receivers window size is 1?

(d) What is the transfer time if 4 concurrent logical channels are used?