Suppose half of the packets get garbled on the link. For a lost packet , B sends a "negative" acknowledgment, triggering a re-transmission by A. How long does it take to send the file?

p25:

P28. Refer again to problem P25. a. How long does it take to send the file, assuming it is sent continuously? b. Suppose now the file is broken up into 20 packets with each packet containing 40,000 bits. Suppose that each packet is acknowledged by the receiver and the transmission time of an acknowledgment packet is negligible. Finally, assume that the sender cannot send a packet until the preceding one is acknowledged. How long does it take to send the file? c. Compare the results from (a) and (b). P25. Suppose two hosts, A and B, are separated by 20,000 kilometers and are con- nected by a direct link of R= 2 Mbps. Suppose the propagation speed over the link is 2.5 . 100 meters/sec. a. Calculate the bandwidth-delay product, R dprop b. Consider sending a file of 800,000 bits from Host A to Host B. Suppose the file is sent continuously as one large message. What is the maximum number of bits that will be in the link at any given time? c. Provide an interpretation of the bandwidth-delay product. d. What is the width (in meters) of a bit in the link? Is it longer than a football field? e. Derive a general expression for the width of a bit in terms of the propaga- tion speed s, the transmission rate R, and the length of the link m