UNIVERSITY EXAMINATIONS: 2011/2012
YEAR II EXAMINATION FOR THE BACHELOR OF SCIENCE IN
INFORMATION TECHNOLOGY
BIT 2303 DISTRIBUTED SYSTEMS
DATE: APRIL 2012 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One and Any other Two Questions
QUESTION ONE
a) Differentiate between loosely coupled systems and tightly coupled systems. (6 Marks)
b) Explain the following forms of transparency (6 Marks)
i. Access
ii. Scalability
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 explain the elements of RPC (Remote Procedure Call).
(8 Marks)
c) Explain the following replication approaches. (7 Marks)
i. Active replication
ii. Passive replication
QUESTION THREE
a) Explain why synchronization of clocks is important in Distributed systems (4 Marks)
b) Differentiate between external synchronization and internal synchronization (6 Marks)
c) State and explain six importances of replication in Distributed Systems. (6 Marks)
d) Differentiate between passive and active attacks citing two examples in each. (4 Marks)
QUESTION FOUR
a) Discuss four advantage and four disadvantages of distributed systems ( 8 Marks)
b) Briefly explain the meaning of the following terms in the context of parallel and distributed
systems. (6 Marks)
i. Mutual exclusion
ii. Dependability
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 a fault. (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 it is in important to detect the fault and rectify the problem. Explain three
techniques used in fault detection and recovery. (6 Marks)
