CSC445 Exercises (Adapted from Peterson and Davies)

Set 1

  1. Calculate the total time required to transfer a 1000-KB file in the following cases, assuming an RTT of 50 ms, a packet size of 1 KBdata, and an initial 2 RTT handshake before data is sent:
    1. The bandwidth is 1.5 Mbps, and data packets can be sent continuously.
    2. The bandwidth is 1.5 Mbps, but after we finish sending eachdata packet we must wait one RTT before sending the next.
    3. The bandwidth is "infinite," meaning that we take transmit time to be zero, and up to 20 packets can be sent per RTT.
    4. The bandwidth is infinite, and during the first RTT we cansend one packet, during the second RTT we can send two packets, during the third we can send four and so on.
  2. Calculate the total time required to transfer a 1.5-MB file in the following cases, assuming an RTT of 80 ms, a packet size of 1 KBdata, and an initial 2 RTT handshake before data is sent:
    1. The bandwidth is 10 Mbps, and data packets can be sent continuously.
    2. The bandwidth is 10 Mbps, but after we finish sending eachdata packet we must wait one RTT before sending the next.
    3. The link allows infinitely fast transmit, but limits bandwidth such that only 20 packets can be sent per RTT.
    4. The bandwidth is infinite, but during the first RTT we can send one packet, during the second RTT we can send two packets, during the third we can send four, etc.
  3. Suppose a 128-kbps point-to-point link is set up between the Earth and a rover on Mars. The distance from the Earth to Mars(when they are closest together) is approximately 55 Gm, and data travels over the link at the speed of light (3X108m/s).
    1. Calculate the minimum RTT for the link.
    2. (b)Calculate the delay X bandwidth product for the link.
    3. A camera on the rover takes pictures of its surroundings andsends these to Earth. How quickly after a picture is taken canit reach Mission Control on Earth? Assume that each image is 5Mb in size.