Assignment 2 (Replacement) Solution

Total of 50 marks. Two hours. Answer the following questions based on topics covered in lectures 4-7. Show your work for any calculations.

Treat this assignment as an open-book individual exam. You may consult any of your class notes or other books or documents, paper or electronic. However, you may NOT discuss questions or share answers with any other person until after the assignment is due.

  1. What is the advantage of modulating a combination of amplitude, frequency and phase rather than just one of the three? [2]
  2. What method does broadband communication use to carry multiple signals simultaneously? [2]
  3. What is an advantage of 5 bit/6 bit encoding over 4 bit/5 bit encoding? [2]
  4. What bandwidth would be needed to send [3]
    1. uncompressed CD-quality sound (44 KHz, 16 bits per sample, two stereo channels) in real time?
      44K x 16 x 2 bits/sec = about 1.4 Mbits/sec.
    2. the same sound if it were compressed to 50% of its original size?
      half the bandwidth or about 0.7 Mbits/sec.
  5. What type of electromagnetic radiation is commonly used in [4]
    1. fibre optic cables?
      visible light
    2. television broadcasts?
      radio waves
    3. wireless LANs?
      infrared
    4. wireless voice transmissions?
      microwaves
  6. Why are conducted media generally more secure and reliable than radiated media? [4]
  7. What factors should a company consider to decide whether to connect to the Internet through a dial-up connection or a leased line? [4]
  8. What two types of cables and connectors are most commonly used by Ethernet network cards? What type of media access does Ethernet use? [5]
  9. Why do servers often have multiple [5]
    1. power supplies?
      • reliability (backup if one fails)
    2. processors?
      • performance (to divide up processing) in multiprocessing systems
    3. hard disks? (two reasons)
      • performance (faster reading and possibly writing)
      • reliability (backup or parity information in case of disk failure)
    4. expansion slots?
      • for multiple disks, network cards, and other shared devices
  10. Why do switches perform better than hubs? [2]
  11. Some networks use a combination of collision detection and collision avoidance. When would each technique be appropriate to use? [2]
  12. What type of media access is used by large corporations like IBM and General Motors who need a guaranteed level of performance? [1]
  13. What computer component stores the address that can be used as a source or destination address of an Ethernet frame? [1]
  14. Which sub-layer of the OSI data link layer determines which computer can send data at what time? [1]
  15. What factors determine how often backups should be performed and which type of backups (e.g. full, differential and/or incremental) should be used? [4]
  16. What is software piracy? Why does it harm software companies? [3]
  17. What are some of the most important features of LAN server software? [5]