UNIVERSITY EXAMINATIONS: 2012/2013
SECOND YEAR EXAMINATION FOR THE BACHELOR OF
SCIENCE IN INFORMATION TECHNOLOGY
BIT 2303 DISTRIBUTED SYSTEMS
DATE: DECEMBER, 2012 TIME: 2 HOURS
INSTRUCTIONS: Answer Question ONE and any other TWO
QUESTION ONE
a) Differentiate between loosely coupled systems and tightly coupled systems.(6 Marks)
b) Explain the following forms of transparencies (6 Marks)
i. Access
ii. Scalability
iii. Replication
c) Describe any three desirable features of a message passing system. (6 Marks)
d) With the help of a diagram explain what a middleware is giving is functions(6 Marks)
e) Describe the term dependability, explaining four requirements for dependability.
(6 Marks)
QUESTION TWO
a) State and describe five importance of IPC (Inter-Process Communication) (5 Marks)
b) With the help of a clearly labeled diagram describe the elements of RPC illustrating
clearly how a remote call is made from a local node to a remote note. (8 Marks)
c) Explain the following replication approaches. (2 Marks)
i. Active replication
ii. Passive replication
d) By use of well labeled diagrams, describe how the bully algorithm is used to elect a
new primary server in event of a failure (5 Marks)
QUESTION THREE
a) Explain why synchronization of clocks is important in Distributed Systems (4 Marks)
b) Differentiate between external synchronization and internal synchronization
(4 Marks)
c) State and explain four importance of replication in Distributed Systems. (4 Marks)
d) Security is a challenge in DS as compared to Centralized Systems. Discuss four
security requirements of any Distributed System showing clearing the kind of attacks
they address. (4 Marks)
e) Differentiate between passive and active attacks citing two examples in each.
(4 Marks)
QUESTION FOUR
a) Discuss any four advantages of Distributed Systems over the Centralized Systems
(6 Marks)
b) Briefly explain the meaning of the following terms in the context of parallel and
distributed systems. (8 Marks)
i. Mutual exclusion
ii. Scalability
iii. Availability.
iv. Name space
c) Describe using diagrams three algorithms for achieving mutual exclusion (6 Marks)
QUESTION FIVE
a) Reliability is one of the desirable characteristics of a Distributed System. Define the
term reliability. (2 Marks)
b) A fault causes failure of a system. Define the term fault giving two types of faults.
(6 Marks)
c) Differentiate between the following terms in reference to reliability (6 Marks)
i. Fault avoidance
ii. Fault tolerance
d) When a failure occurs is in important to detect the fault and rectify the problem.
Explain three techniques used in fault detection and recovery. (6 Marks)
