Problem Set #1 (20 questions) Chapters 1 & 2 Due Wednesday, September 17th by 11:55pm Problem 1 Calculate the total time required to transfer a 1,000 KB file in the following cases, assuming an RTT of 100 ms, packet size of 1 KB data, and an initial 2X RTT of "handshaking" before data is sent. (a) The bandwidth is 1.5 Mbps and data packets are sent continuously (b) The bandwidth is 1.5 Mbps, but after we finish sending each data packet, we must wait one RTT before sending the next (c) The bandwidth is "infinite", meaning that we take transmit time to be zero, and up to 20 packets may be sent per RTT (d) The bandwidth is infinite, and during the first RTT we can send one packet (21-‐1), during the second RTT we can send two packets (22-‐1), during the third we can send four (23-‐1), and so on. (A justification for such an exponential increase will be given in Ch 6) Problem 2 Suppose a 100-‐Mbps point-‐to-‐point link is being setup between Earth and a new lunar colony. The distance from the moon to Earth is approx 385,000 km, and data travels over the link at the speed of light-‐ 3 x 108 m/s. (a) Calculate the minimum RTT for the link (b) Using the RTT as the delay, calculate the delay X bandwidth product for the link (c) What is the significance of the delay X bandwidth product in (b) (d) A camera on the lunar base takes pictures of Earth and saves them to digital format on a disk. Suppose Mission Control (on Earth) wants to download the most current image, which is 25 MB. What is the minimum amount of time that will elapse between when the request for the data goes out, and the transfer is finished? Problem 3 Calculate the latency from first bit sent to last bit received for the following: (a) A 10-‐Mbps Ethernet with a single store-‐and-‐forward switch in the path, packet size of 5,000 bits. Assume that each link introduces a propagation delay of 10 micro seconds, and that the switch begins retransmitting immediately after it has finished receiving the packet. Computer Networks 5th Edition Exercises Chapter 1: 1.3, 1.5, 1.8, 1.11, 1.12, 1.18, 1.19, 1.22, 1.24, 1.36 Chapter 2: 2.1, 2.2, 2.5, 2.13, 2.14, 2.40, 2.44