KNEC Diploma in Information Technology (Information Technology) Data Communication  Question Paper

Exam Name: Data Communication 

Course: Diploma in Information Technology (Information Technology)

Institution/Board: KNEC

Exam Year:2004

1. (a) Describe a Local Area Network (LAN) and state TWO advantages derived from it. (4 marks)
(b) State FOUR basic network components explaining their functions. (6 marks)
(c) (i) List THREE types of networking cables.
(ii) State THREE factors that influence the choice of a cable. (6 marks
(d) State FOUR techniques used to ensure security in a computer system. (4 marks)
2. (a) Distinguish between serial and parallel transmission. (4 marks)
(b) With the aid of a diagram, explain the operation of an IBM-Token ring protocol. (4 marks)
(c) With the aid of a labelled reference model, explain the main functions of the layers of the x25 protocol. (9 marks
(d) State THREE factors to consider while selecting a line coding technique. (3 marks)
3. (a) Assuming that the base band is a series of rectangular pulses, desribe the following methods of modulation.
(i) Amplitude shift keying.
(ii) Frequency shift keying. (10 marks)
(b) Explain the difference between base band and broadband signalling. (4 marks)
(c) Describe the operation of each of the following applications.
(i) www
(ii) e-mail
(iii) telnet (6 marks)
4. (a) Using a block diagram, describe the functions of the first FOUR layers of the open systems interconnections (OSI). (10 marks)
(b) State TWO functions of the front-end-processor. (2 marks)
(c) Draw a wave diagram for the data input 101011100, showing how unipolar NRZ, polar NRZ, NRZ-inverted and Bipolar line codings are used. (8 marks)
5. (a) Describe the working principle of each of the following:
(i) Message routing
(ii) Session routing
(iii) Packet flooding
(b) State THREE advantages and THREE disadvantages of layered architecture. (6 marks)
(b) Using an example, explain how Cyclic Redudancy Check (CRC) is used in error control. ( 5 marks)
(d) Determine and explain the hamming distance between 100100 and 101010. (3 marks)
6. (a) TCP/IP is the most commonly used set of communication protocols over the internet. Illustrate the TCP/IP protocol suite and describe its operations in terms of layers. (9 marks)
(b) With the aid of a labelled signal flow diagram, describe the function of the CCITT X21 interface lines. (8 marks)
(c) Distinguish between idle-detect time-out and non-productive receive time-out. (3 marks)
7. (a) Describe the following multiplexing schemes and show their frequency time graphs.
(i) Time division multiplex (TDM)
(ii) Frequency division multiplex (FDM) (8 marks)
(a) Explain the following techniques:
(i) Circuit switching
(ii) Message switching
(iii) Packet switching (6 marks)
(c) State ONE limitation of each technique in (b) above. (3 marks)
(d) State THREE properties of data gram. (3 marks)
8. (a) Describe the following
(i) DTE
(ii) DCE (4 marks)
(b) Explain the following terms giving an application for each.
(i) Simplex
(ii) Half-duplex
(iii) Full-duplex (6 marks)
(c) With the aid of frame formats, explain the following methods of data transmission.
(i) Asynchronous
(ii) Synchronous (6 marks)
(d) Explain the internet Domain Name System (DNS).



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