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DTS620S - DISTRIBUTED SYSTEMS - 1ST OPP - NOV 2023 |
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nAmlBIA unlVERSITY
OF SCIEnCE Ano TECHnOLOGY
FACULTYOFCOMPUTING AND INFORMATICS
DEPARTMENTOF COMPUTERSCIENCE
QUALIFICATION:BACHELOROF COMPUTERSCIENCE,SYSTEMSADMINISTRATION
QUALIFICATIONCODE: 07BACS
LEVEL:6
COURSENAME: DISTRIBUTEDSYSTEMS
COURSECODE: DTS620S
DATE: November 2023
PAPER:THEORY
DURATION: 2 HOURS
MARKS:70 (100%)
EXAMINERS
MODERATOR
FIRSTOPPORTUNITYEXAMINATION QUESTIONPAPER
MS ALBERTINASHILONGO
PROF. JOSE QUENUM
INSTRUCTIONS
1) Answer ALL the questions on the answer scripts provided.
2) Be guided by the number of marks allocated when answering the questions.
3) Write clearly and neatly.
4) Show all your calculations/work.
5) Number your questions clearly.
THIS QUESTION PAPERCONSISTSOF 3 PAGES(Including this front page)
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Question 1:
[26 Marks]
a) Explain why the following systems can be classified as real-world applications of distributed
systems?
(4)
I. Web:
II. Civil Aviation:
b) Why is clock synchronization a key feature in distributed systems?
(2)
c) List and explain various key challenges in designing and managing distributed systems. (8)
d) Explain the role of middleware in supporting the development of distributed applications
and services.
(4)
e) Explain the concept of fault tolerance in distributed systems and discuss various features
designed within distributed systems to handle failures.
(8)
Question 2
a) Explain the concept of independent failure in distributed systems.
[20 Marks]
(3)
b) Group Communication paradigm routes messages via multicast, using various communication
protocols; at times the message sent is never received by the receiver; Explain the causes of
such scenarios.
(3)
c) If a communication paradigm is asynchronous, is it also time and space uncoupled? motivate
your answer with examples as appropriate.
(4)
d) Many of the information resources that are made available and maintained in distributed
systems have a high intrinsic value to their users. Their security is therefore of considerable
importance. List and explain the 3 security components of any distributed systems
(6)
e) Discuss how the following security challenges can be experienced in distributed systems. (4)
I. Denial of service attacks:
II. Security of Mobile code:
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Question 3
[24 Marks]
a) Using Java codes, create an application that creates a MulticastSocket class to create UDP
multicast sockets to receive datagram packets sent to a multicast IP address and received by
another process. The following instruction should guide you, only on the sender side.
(12)
• Objects (MulticastSender and MulticastReceiver
• Connectionless oriented, the receiver needs to start first.
• On the Multicast receivers
• Specify Class DIP address starting from (225.1.2.3)
• Open any available multicast socket on the UDP port (3456)
• Call the join group method on the multicast socket to join the multicast group.
• Message to be received should be 150 bytes (create an array).
• Create a datagram socket for the expected packets.
• Create and call the receiver method on the Multicast socket to be able to receive the
message.
• Display the message that was received.
• Close the socket.
b) Consider figure 1 below that shows 3 processes (Pl, P2, and P3) executing in a distributed
System with various messages passing between the processes. Assume that initial logical clock
values are all initialized to 0.
Using Vector Clock, for each event shown in the figure, list all the packet's logic clocks. (12)
P3: ____
-111•-="------------••------------
Exam Ends
Total 70 Marks
3