UNIVERSITY EXAMINATIONS: 2013/2014
ORDINARY EXAMINATION FOR THE BACHELOR OF SCIENCE
IN INFORMATION TECHNOLOGY
BIT 2303 DISTRIBUTED SYSTEMS (DAY)
DATE: APRIL, 2014 TIME: 2 HOURS
INSTRUCTIONS: Answer Question ONE and any other TWO
QUESTION ONE
a) Define the following terms [6 Marks]
i. Distributed File System (DFS)
ii. Middleware
iii. Replication
b) With the help of well labeled diagrams illustrate your understanding of synchronous
communication and asynchronous communication [6 Marks]
c) Draw the diagram of RPC Implementation model and illustrate how a message is
passed form the client to the server [8 Marks]
d) There are two broad approaches to synchronizing the clocks so as to get a consistent
view of time in Distributed Systems. Mention and explain them [4 Marks]
e) Discuss any four security requirement in any DS highlighting the attacks to each of
the requirements [6 Marks]
QUESTION TWO
a) There two forms of communication when processes are executing: original sharing
and copy sharing. Using well labeled diagrams differentiate the two. [5 Marks]
b) Describe the Sun Network File System (NFS) [5 Marks]
c) With the help of a diagram illustrate the basic file replication architectural model
[6 Marks]
d) Using simple diagrams, discuss differences between local procedure calls and remote
procedures calls. [4 Marks]
QUESTION THREE
a) Using a well labeled diagram illustsrte how the Cristaian algorithm achieves external
synchronization from the UTC with Local Areas Networks(LANs) . [6 Marks]
b) Explain why Chrstain algorithm cannot work to achieve synchronization within Wide
Area Networks (WANs) [4 Marks]
c) Discuss six importance of eplication is Distributed Systems [6 Marks]
d) Briefly explain the meaning and importance of the following terms in the context of
parallel and distributed systems. [4 Marks]
i. Mutual exclusion
ii. Extensibility
iii. Availability
iv. Name space
QUESTION FOUR
a) Describe using diagrams three algorithms for achieving mutual exclusion [6 Marks]
b) Reliability is one of the desirable characteristics of a distributed system. Define the
term reliability. [2 Marks]
c) A fault causes failure of a system. Define the term fault giving two types of a fault.
[6 Marks]
d) Differentiate between the following terms in reference to reliability [6 Marks]
i. Fault avoidance
ii. Fault tolerance
QUESTION FIVE
a) Differentiate between loosely coupled systems and tightly coupled systems.[6 Marks]
b) In order to provide concurrency transparency, the resource sharing mechanism of the
DS must have four properties. With appropriate examples and diagrams where
possible, discuss these properties. [6 Marks]
c) Discuss the following forms of transparency [4 Marks]
i. Failure transparency
ii. Scaling transparency.
d) Describe the term dependability, explaining any three requirements for dependability.
[4 Marks]
