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CMN620S - COMMUNICATION NETWORKS - 2ND OPP SUPL - JAN 2023 |
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n Am I BI A un I VE RS ITV
OF SCIEnCE Ano TECHnOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION:BACHELOR OF COMPUTER SCIENCEIN CYBERSECURITY
BACHELOR OF COMPTER SCIENCE
QUALIFICATIONCODE: 07BCCS; 07BACS
LEVEL: 7
COURSE: COMMUNICATION NETWORKS
COURSECODE: CMN620S
DATE:JANUARY 2023
SESSION: 2
DURATION: 2 HOURS 30 MINUTES
MARKS: 70
SECONDOPPORTUNITY/ SUPPLEMENTARYEXAMINATION QUESTION PAPER
EXAMINER(S}
MR. NASIMANE EKANDJO
DR. MERCY CHITAURO
MS. LOINI IIYAMBO
MODERATOR:
MR. EDWARD NEPOLO
THIS QUESTION PAPERCONSISTSOF 4 PAGES
(Excluding this front page)
INSTRUCTIONS
1. Answer ALL the questions.
2. Write clearly and neatly.
3. Number the answers clearly.
4. When answering questions you should be guided by the allocation of
marks. Do not give too few or too many facts in your answers.
PERMISSIBLEMATERIALS
1. Non-programmable calculator.
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Question 1
Indicate whether the following statements are true or false.
[4]
1.1 An ARP package has fields containing link-layer addresses as well as network-layer
addresses.
1.2 Routers operate at network layer by utilising datagrams, while switches operate at
link layer by utilising frames.
1.3 Routers operate at network layer by utilising frames, while switches operate at link
layer by utilising datagrams.
1.4 If a computer has two network cards, it also means that it must have two layer-2
addresses.
Question 2
Choose the correct answer from the questions below:
[6]
2.1 What is the broadcast address of 200.70.55.1 /18?
a) 200.70.15.255
b) 200. 70.63.255
c) 200.70.68.255
d) 200.70.31.255
2.2 Open Shortest Path first (OSPF)disseminates information in the form of __ .
a) unicast
b) multicast
c) broadcast
d) anycast
2.3 Which class of IP Addresses has the least host addresses available by default?
a) A
b) B
c) C
d} A and B
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2.4 On a VLSM network, which mask should you use on point-to -point WAN links in
order to reduce the wastage of IPA addresses?
a) /28
b) /29
c) /30
d) /31
2.5 Link state routing protocols exchange the following information with one another.
(Choose two).
a) Link state for every link
d) A link and a state for every destination
c) Hello packets with every link
d) Hello packets with every neighbour
e) Link state for every state
Question 3
3.1 List three major components of electronic mail.
[3]
3.2 Which mail access protocol allow users to organize messages in folders and keeps
user state across sessions?
[1]
Question 4
Assume packets are being transmitted from a host source to a host destination through
some routers.
4.1 Explain how does loss and delay of such packets can occur.
[2]
4.2 Explain how a router can overcome this loss and delay.
[2]
Question 5
5.1 OSPFwas conceived as the successor to RIP.As such, it has a number of advanced
features. Explain any three such advances of OSPF.
[3]
5.2 Define RIP as a routing protocols with respect to which mechanism do routers
running this protocol obtain knowledge about their neighbours?
[2]
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Question 6
6.1 What are the three contents of an ARP table?
[3]
6.2 In a switched network, host A wants to communicate to host B on the same LAN.
Host A does not have host B's MAC address in its ARP table. Explain how host A can
still manage to communicate to host B.
[3]
6.3 Explain the concept of flooding that is used by link-layer switches.
[2]
Question 7
7.1 In a form of a table as below, differentiate between TCP and UPD.
[6]
TCP
•
•
•
UDP
•
•
•
7.2 Explain how TCP can be enhanced in terms of security services.
[2]
7.3 Give two example of a protocol/application that utilises UDP.
[2]
Question 8
Consider the topology below and answer the questions that will follow.
192.16B.100.0 /30
200.200.200.0 /30
1'92.16B.200.0 /30
j
172.16.20.0 /24
172.16.30.0 /24
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,:)
PC-PT
PC3
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8.1 After configuring the above topology with a routing protocol, state any of the
networks that will be learned by the Prosperita router. (Mention two).
[2]
8.2 Suggest a possible default gateway address for PC_2.
[1]
8.3 The suggested IP address for PC_3is the last usable IP address for the subnet. Write
down this IP address.
[2]
8.3 State the IP addresses of the interfaces for the serial connection 192.168.100.0 /30.
[2]
Question 9
Given the IP Addresses below, provide the network number and the broadcast address.
9.1 172.18.120.120 /16
Network number:
[2]
Broadcast Address:
[1]
9.2 192.168.150.70 /26
Network number:
[2]
Broadcast Address:
[1]
Question 10
As a Network Administrator of a company, you are given a class B IP address block:
172.27.0.0 /18
Utulising CIDR, calculate the subnets that will be assigned to each department of the
company. You are informed that each department requires 500 users:
As per your subnetting, clearly indicate:
10.1 Number of subnets that will be created.
[2]
10.2 Number of usable hosts per subnet.
[2]
10.3 List the first three subnets.
(6 (2 for each)]
10.4 State the usable host range for each subnet mentioned in 10.3.
(6 (2 for each)]
End of exam
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