BIT2303  DISTRIBUTED SYSTEMS .

UNIVERSITY EXAMINATIONS: 2017/2018
EXAMINATION FOR THE DEGREE OF BACHELOR OF SCIENCE
IN INFORMATION TECHNOLOGY/ BACHELOR OF BUSINESS IN
INFORMATION TECHNOLOGY
BIT2303 DISTRIBUTED SYSTEMS
FULL TIME/PART TIME/DISTANCE LEARNING
DATE: APRIL 2018 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.

QUESTION ONE: 30 MARKS (COMPULSORY)
a) Define a Distributed System 3 Marks
b) By use of well labeled diagrams illustrate three key differences between distributed
systems and centralized systems 6 Marks
c) Differentiate between NOS (Network Operating Systems) and DOS (Distributed
Operating Systems) 6 Marks
d) State and briefly explain four security goals, highlighting the threats to these goals
6 Marks
e) Outline three advantages of replication in Distributed Systems 3 Marks
f) Discuss how the following clock synchronization centralized algorithms work to
achieve external synchronization. 6 Marks
i. Cristain algorithm
ii. Berkeley algorithm
QUESTION TWO: 20 MARKS
a) Discuss four advantages of Distributed Systems over Centralized systems.
4 Marks
b) Briefly describe all the components of a Distributes Systems 6 Marks
c) Discuss the four models of middleware 4 Marks
d) Describe the following models of Distributed Systems 6 Marks
i. Client-Server Model
ii. Peer-to-Peer Model
QUESTION THREE: 20 MARKS
a) Explain the relation between an error, a fault and a failure 2 Marks
b) State and briefly explain four drawbacks of Distributed Systems 4 Marks
c) Describe any three desirable features of a Message Passing System. 6 Marks
d) With the help of a clearly labeled diagram illustrate the implementation of the RPC
mechanism. 8 Marks
QUESTION FOUR: 20 MARKS
a) Define the term reliability 2 Marks
b) A fault causes failure of a system. Define the term fault giving two types of a fault.
6 Marks
c) Differentiate between the following terms in reference to reliability 6 Marks
i. Fault avoidance
ii. Fault tolerance
d) Describe the following forms of transparencies showing their importance in
Distributed Systems 6 Marks
i. Migration Transparency
ii. Replication Transparency
iii. Access Transparency
QUESTION FIVE: 20 MARKS
a) Differentiate between external synchronization and internal synchronization
4 Marks
a) Discuss the following replication approaches. 6 Marks
i. Active replication
ii. Passive replication
b) Briefly discuss the meaning of the following terms in the context of parallel and
Distributed Systems. 4 Marks
i. Mutual exclusion
ii. Dependability
iii. Availability.
iv. Name space
c) Describe using diagrams three algorithms for achieving mutual exclusion
6 Marks

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