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CMN620S - COMMUNICATION NETWORKS - 2ND OPP - JAN 2020 |
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NAMIBIA UNIVERSITY
OF SCIENCE AND TECHNOLOGY
Faculty of Computing and Informatics
Department of Computer Science
QUALIFICATION: BACHELOR OF COMPUTER SCIENCE, BACHELOR OF COMPUTER SCIENCE IN
CYBER SECURITY, BACHELOR OF ENGINEERING: ELEC. & TELECOM
QUALIFICATION CODE: 07BACS, 07BCCS,
35BEET
LEVEL: 6
COURSE: Communication Networks
COURSE CODE: CMN620S
DATE: January 2020
DURATION: 2 hours
MARKS: 50
SUPPLEMENTARY / SECOND OPPORTUNITY EXAMINATION QUESTION PAPER
EXAMINER(S)
Peter Gallert
MODERATOR:
Prof Dharm Singh Jat
THIS QUESTION PAPER CONSISTS OF 2 PAGES
(Excluding this front page)
INSTRUCTIONS
1) Answer all questions.
2) When answering questions you should be led by the allocation of marks.
3) Write clearly and neatly in your examination book. Answers that appear only on the
question paper cannot be marked.
PERMISSIBLE MATERIALS
1) Calculators are not allowed!
2) Do not use or bring into the examination venue books, mobile devices and other
material that may provide you with unfair advantage. Should you be in possession of
such material right now, draw the attention of the examination officer or invigilator.
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Faculty of Computing and Informatics, Department of Computer Science
CMN620S: Theory Exam, Supplementary / 2°¢ opportunity
1. Apizza baker in Windhoek plans to expand business by accepting Internet orders. They
ask you to design their small network. The following devices need to be accommo-
dated:
e 10 user PCs
e Web server to enable Internet orders and payment
e Email server to enable further communication with customers
e Print server to print accepted orders for the bakery
(a) Design a simple network for the pizza bakery, using no more than 2 routers and
(6)
3 switches. Place the devices listed above accordingly (the ten PCs can be one
symbol). Indicate which device to connect to the Internet.
(b) The service provider has allocated the small public IP address block 196.1.1.0
(4)
/28 to the bakery. Internally, private IP addresses should be used. Indicate the IP
addressing for your network.
2. Consider the network below. The routers run OSPF, the LAN interconnecting the routers
already has IP addresses from network 10.0.0.0 /8, as indicated. The physical LAN
with 75 users is logically divided into three VLANs: VLAN 2 (Admin) with 25 users, VLAN
3 (Reception) with 45 users, and VLAN 4 (IT) with 5 users.
75 users
85 users
20 users
50 users
(a) Provide IP addresses for all subnets except the 10.0.0.0 /8LAN, using the pri-
(12)
vate IP address block 192.168.0.0 /16. Subnet according to Variable—Length
Subnet Masking (VLSM) principles. Provide your answer on the answer sheet,
not on the question paper, using clear network names like “LAN 85” and “Admin
VLAN”.
(b) If the routers were running RIPvi as routing protocol instead of OSPF, how would
(6)
the IP addressing have to change?
(i) In general—What would need to be considered to make this change? [2
marks]
(ii) Why would a change to the existing IP addressing be necessary? [2 marks]
(iii) Give an example of how LAN 50 could be supplied with IP addresses in this
case. [2 marks]
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Faculty of Computing and Informatics, Department of Computer Science
CMN620S: Theory Exam, Supplementary / 2"? opportunity
3. Explain the operation of a router in terms of the OSI model of computer networking.
(a) On which layers of the OSI model does a router operate, and what are its respon-
(4)
sibilities per layer?
(b) What types of encapsulation and decapsulation does a router perform, and why?
(4)
4. Arouter has a Loopback interface with an IP address of 105.105.105.105 /16.
(a) What is the command on the router to enable routing for this Loopback
(4)
(i) ...when running the Routing Information Protocol (RIP)? (2 marks)
(ii) ...when running Open Shortest Path First (OSPF)? (2 marks)
(b) After the Loopback network has been correctly configured, what information about
(4)
this Loopback will be sent to other routers?
(i) ...when running the Routing Information Protocol (RIP)? (2 marks)
(ii) ...when running Open Shortest Path First (OSPF)? (2 marks)
(c) After the network has converged, which routing protocol data will be sent out via
the Loopback interface?
(i) ...when running the Routing Information Protocol (RIP)? (1 mark)
(ii) ...when running Open Shortest Path First (OSPF)? (1 mark)
5. Which network design goals are supported by the following actions? Mention one goal
per action, and explain briefly.
(a) Installing a second power supply into each of the public servers
(b) Using a proxy server for HTTP and FTP
End of question paper
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