UNIVERSITY EXAMINATIONS: 2013/2014
ORDINARY EXAMINATION FOR THE BACHELOR OF SCIENCE
IN INFORMATION TECHNOLOGY
BIT 2303 DISTRIBUTED SYSTEMS
DATE: AUGUST, 2014 TIME: 2 HOURS
INSTRUCTIONS: Answer Question ONE and any other TWO
QUESTION ONE: 30 MARKS (COMPULSORY)
a) Differentiate between Network Operating Systems (NOS) and Distributed Operating
System (DOS). (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) Using well labeled diagrams, differentiate between synchronous communication and
asynchronous communication. (6 Marks)
d) Using appropriate examples describe the following forms of transparency
i) Location transparency
ii) Migration transparency (6 Marks)
e) Describe the six components that make up a Distributed System. (6 Marks)
QUESTION TWO: 20 MARKS
a) Define the term “message” in the context of Inter-Process Communication (IPC).
(2 Marks)
b) By use of a diagram describe the structure of a message. (5 Marks)
c) Discuss four advantages of replication in a Distributed System. (4 Marks)
d) Describe the basic file replication architectural model (5 Marks )
e) Discuss two mechanisms of improving fault tolerance in Distributed Systems
(4 Marks)
QUESTION THREE: 20 MARKS
a) Differentiate between local procedure call (lpc) and a remote procedure call (rpc)
(4 Marks)
b) Discuss the similarities between a Procedure Call (PC) and the Remote Procedure
Call (RPC). (6 Marks)
c) Describe the following elements of the RPC model highlighting their functionalities.
(8 Marks)
i) Client stub
ii) Server stub
iii) Client RPCRuntime
iv) Server RPCRuntime
d) Highlight the difference between Message Passing and Remote Procedure Calls as
IPC mechanism (2 Marks)
QUESTION FOUR: 20 MARKS
a) Define a critical system. (2 Marks)
b) Using examples describe the three types of critical systems (6 Marks)
c) Define the following concept used in synchronization (3 Marks)
i) Skew
ii) Clock drift
iii) Clock drift rate
d) Differentiate between internal and external synchronization (4 Marks)
e) Describe the Berkeley algorithm for achieving synchronization in clocks within
Distributed Systems. (5 Marks )
QUESTION FIVE:20 MARKS
a) Differentiate between a process and a program (2 Marks)
b) Define the term transparency and explain its importance in the design of DOS.
(3 Marks)
c) State and explain four attacks on Distributed Systems (4 Marks)
d) Describe five security requirements of DOS (5 Marks)
e) Discuss three classes of faults common in Distributed Systems (6 Marks)
