Consider a GoBackN ARQ system with W = 8. Assume that the sender sends the first frame (sequence numbered 1) at time 0. The transmission time for all packets is the same and is equal to t, r is the propagation delay for either frames or ACKs, and r= 3t . The transmission time is effectively zero for ACKs. The sender uses a timeout of 10t starting from the end of the frame transmission.

By curious mischance, every eighth time that the sender attempts a frame transmission (whether an original frame transmission or a retransmission), the frame gets lost. ACKs never get lost.

1. Draw a timing diagram from time 0 to the time when the first retransmission occurs at the sender, for some frame i, indicating all frame, ACK transmission and reception events with times and sequence numbers
2. Under these conditions, when will the frame i be correctly received at the receiver for the first time?