Consider a sender having an infinite number of frames to send, which we index as 0, 1, 2, .... Assume the transmission delay of each frame is 2t, the ACK transmission time is t, the propagation delay is 3t and symmetric on both directions, and the timeout value is T = 8t starting from the end of frame transmission onto the link. The first frame is sent out at time 0.

A. Draw the timing diagram of SWP with 4 frames (numbered 0-3) being sent and acknowledged, where frame #2 (the third frame) is lost. List the sequence number of each frame at the sender side, and explicitly indicate the timeout in the diagram.

B. In the above SWP operations, what is the time when ACK of frame 4 is received? What is the efficiency of the SWP operation from the beginning to the end of transmission of frame 4 (acked)? Note: The efficiency is defined as the fraction of time when the sender is busy sending "useful" packets, i.e., not including lost packets or duplicate retransmissions.

C. Draw the timing diagram of GBN with N = W = 3 (the sender has sufficient buffer) and 4 frames being sent and acknowledged, where frame #3 is queued for an additional 3t time at the receiver before an ACK is generated. List the sequence number of each frame at the sender side, the sender's window of sequence numbers of outstanding frames at each receipt of an ACK, and explicitly indicate the timeout in the diagram.

D. In the above GBN operations, what is the time when the first ACK of frame 4 is received? What is the efficiency of the SWP operation from the beginning to the end of transmission of frame 4 (acked)?

E. Explain what will happen if the sequence number space has exactly the same number of sequence numbers as the number of allowed maximum number of outstanding frames, e.g., when N = W = 10, and the sequence numbers available are only 0-9.

F. Explain the trade-off made between GBN and SRP, in other words, each of their pros and cons.