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Sci 312: Distributed Systems Question Paper
Sci 312: Distributed Systems
Course:Bachelor Of Science In Computer Science|Bachelor Of Science In Information Technology
Institution: South Eastern Kenya University question papers
Exam Year:2016
SOUTH EASTERN KENYA UNIVERSITY
UNIVERSITY EXAMINATIONS 2016/2017
SECOND SEMESTER EXAMINATION FOR THE BACHELOR OF SCIENCE IN COMPUTER SCIENCE & BACHELOR OF INFORMATION TECHNOLOGY
SCI 312: DISTRIBUTED SYSTEMS
DATE: 12TH APRIL, 2017 TIME: 1.30 -3.30 PM
INSTRUCTIONS TO CANDIDATES
• Section A(Compulsory)
• Answer ANY TWO questions from section B
Question One
a. Define the term distributed system. (1 Mark)
b. Justify the need to design a system as a distributed system. (3Marks)
c. Differentiate between a local call and a remote call. (2 Marks)
d. With aid of a diagram describe what Middleware is. (2Marks)
e. Distinguish between call by reference and call by value. (2 Marks)
f. Describe the client server model. (2Marks)
g. i. Define the term atomic multi-cast as used group communication. (1 Mark)
ii. Justify the need for atomic multi-cast when dealing with replicated data. (2 Marks)
h. Explain distributed 2-phase commit. (3 Marks)
i. Using an illustration explain the Bully algorithm for electing a leader. (4 Marks)
j. What is a leap second. (2 Marks)
k. Highlight four applications of group communication. (4 Marks)
l. Explain Cristian’s algorithm. For Clock synchronization (2Marks)
SECTION B (40 marks)- Answer any Two Questions
Question Two
a.
i. Suppose there are three processes A,Band C. All clock runs atthe same rate but initially A’s
clock reads 10, B’s clockC ’sreadsclock0andreadsA’s5.clock,AsendsAtatime 10 messageto B, this message takes 4 units of time to reach B. B then waitsone unit of time and then sends a message onto C which takes 2units of time to reach C. Assuming that the system implementsLamport’s timestamps draw a pictur and explain how the timestamps are obtained. (6 Marks)
ii. What does it mean for two events to be concurrent and what isthe relation of the Lamport timestamps of the two events. (2 Marks).
b. With an aid of a diagram, describe remote procedure call between a client and a server.
(6 Marks)
c. Explain the following file access models:
i. Remote service; (2 Marks)
ii. Upload download. (2 Marks)
d. It is said that it is easier to recover a stateless server as opposed to a stateful server.
Justify this claim. (2 Marks)
Question Three
a. Explain the three components of a distributed file system. (6 Marks)
b. With an aid of a diagram, explain distributed mutual exclusion. (4 Marks)
c. Consider a distributed system comprising of eight processes namely p1, p2, p3, p4,p5,p6,p7,p8.Process p2 and process p5 concurrently discovers that process p8 is down and
call for election based on a ring algorithm. Using diagrams illustrate the process of getting a
new leader. (6 Marks)
d. i. Justify the use of replicated servers for fault tolerance in a distributed system.
(2 Mark)
ii.Distinguish between tightly coupled system and loosely coupled system. (2 Marks)
Question Four
a.i. Define the term transparency as used in distributed systems. (2 Marks)
ii. Explain five types of transparencies. (5 Marks)
b. Using an example illustrate berkely algorithm of clock synchronization. (5 Marks)
c. Distinguish between the following terms:
i. Idempotent operation and non idempotent operation; (2 Marks)
ii. Blocking and non- blocking synchronization semantics; (2 Marks)
d.Explain the ACID properties of transactions. (4Marks)
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