UNIVERSITY EXAMINATIONS: 2015/2016
EXAMINATION FOR THE DIPLOMA IN BUSINESS/ INFORMATION
TECHNOLOGY
DBIT401 COMPUTER NETWORKS
DATE: AUGUST 2016 TIME: 1½HOURS
INSTRUCTIONS: Answer Any THREE Questions.
QUESTION ONE
a) Briefly describe THREE (3) advantages offered by a fibre-optic cable that are not
provided by copper wire. [3 Marks]
b) State ONE (1) disadvantage of replacing copper cables with fibre-optic cable. [1 Marks]
c) Briefly describe the difference between multimode fibre-optics and monomode fibreoptics [6 Marks]
d) Briefly explain what is meant by a repeater and briefly discuss how it works. [4 Marks]
e) Briefly explain FIVE (5) features of a network hub. You should refer to how a network
hub functions. [5 Marks]
f) Define the term Network [1 Mark]
QUESTION TWO
a) With the aid of a diagram, explain how a Man-in-the-Middle attack operates. [4 Marks]
b) State THREE (3) features of message encryption. [3 Marks]
c) Explain why encryption is an important measure in preventing successful Man-in theMiddle attacks [3 Marks]
d) Explain how a firewall is used to create a Demilitarised Zone (DMZ). You should support
your answer with a diagram that is clearly labelled. [4 Marks]
e) State THREE (3) reasons why it is common for networks to have multiple layers of
firewall protection [3 Marks]
f) List any three network types [3 Marks]
QUESTION THREE
a) Describe in detail the role of the Network Layer in a computer network. [2 Marks]
b) State FIVE (5) protocols that operate on the Network Layer. [5 Marks]
c) A digital transmission system uses a coding scheme that defines a symbol as a voltage
that can have one of eight possible values. If the system operates at a transmission rate of
1,000 symbols per second, determine the data transmission rate measured in:
i. Baud [2 Marks]
ii. Bits per second [2 Marks]
d) Define the term virtual circuit [4 Marks]
e) A user wishes to establish a connection from their laptop to a server via the Internet
using the TCP protocol. By considering the protocol messages that TCP generates,
explain how a virtual circuit is established between the laptop and server using TCP.
[3 Marks]
f) Give any two advantages of network protocols [2 Marks]
QUESTION FOUR
a) In contrast to TCP, UDP is described as a connectionless protocol. Briefly explain how
data is transmitted between two computers using the UDP protocol. [4 Marks]
b) In classful addressing, the IP address space is divided into 5 classes. Indicate the classes
of each of the following address expressed in binary. Indicate how the class was
identified.
i. 00000001 00001011 00001011 11101111
ii. 11000001 10000011 00011011 11111111
iii. 11110011 10011011 11111011 00001111 (6 Marks)
c) A host was given the IP addresses 192.168.3.219 /27. Consider this address and indicate:
i. The network address to which the host belongs.
ii. The network broadcast address to which the host belongs.
iii. The total number of hosts available in the network (6 Marks)
d) Describe the concept of classless addressing, indicating the reason why it was proposed
and providing an example of a classless IP address. (4 Marks)
QUESTION FIVE
a) Define the term topology and state the difference between logical and physical network
topologies [4 Marks]
b) Explain advantages of wireless over wired networks [3 Marks]
c) Explain the Factors to consider when choosing a Transmission Media [5 Marks]
d) IP addresses can be assigned either statically or dynamically. Explain the difference
between the two stating where each is appropriate [5 Marks]
e) There are 3 different transmission modes characterized according to the direction of the
exchanges, state and explain three such transmission modes [3 Marks]
