NATIONAL OPEN UNIVERSITY OF NIGERIA

UNIVERSITY VILLAGE, PLOT 91, CASDASTRAL ZONE, NNAMDI AZIKIWE EXPRESS WAY, JABI, ABUJA.
FACULTY OF SCIENCES
OCTOBER 2014 EXAMINATION

Course Code:                     CIT 303

Time Allowed:                   3hrs

Title:                                      Principles of Communication Technology

Instruction: Attempt any five (5) questions

1a. Define Data Communications                                                                                                                              (5 marks)

1b. What are the three basic modes of operation that can exist for any network connection, communications channel, or interface?                                                                                                                                                           (6 marks)

1c. List three of the basic elements / components of Data Communications.                                        (3 marks)

2a. A network must meet certain important criteria amongst which is one of them is performance, how can a network performance be measured?

2b. State two factors that determine the performance of a network.                                                      (4 marks)

2c. Explain two different types of computer network connection?                                                            (6 marks)

3a. Define network protocol?

3b. What are the key elements of protocols?                                                                                                      (6 marks)

3c. Which layers on the OSI Model are referred to as network support layers and which layers are the user support layers?                                                                                                                                                                                                 (6 marks)

4a. Define network topology.                                                                                                                                     (6 marks)

4b. State 4 advantages of fiber-optic cable over metallic cable (twisted-pair or coaxial)                   (4 marks)

4c. State 2 disadvantages of fiber-optic cable over metallic cable (twisted-pair or coaxial)              (4 marks)

5a. A network is a set of connected devices. Whenever we have multiple devices, we have the problem of how to connect them to make one-one communication possible. One solution is to make a point - to-point connection between each pair of devices (a mesh topology) or between a central device and every other device (a star topology). These methods, however are impractical and wasteful when applied to very large networks. Suggest a better practical solution and give reasons for your solutions.         

5b. Describe three characteristics of microwave propagation.                                                                     (3 marks)

5c. List three traditional switching methods and the method you think are the most common switching method today.                                                                                                                                                                                 (4 marks)

6a. What is cryptography?                                                                                           

6b. Outline the three types of keys in cryptography?

6c. Differentiate between Symmetric-key cryptography and Asymmetric-key cryptography.

7a. Explain the following terms: Message confidentiality, Message Integrity, Message Authentication, Message non-repudiation and Entity-authentication.

7b. What is cipher?                                                                                                                                                          (4 marks)