UNIVERSITY EXAMINATIONS: 2016/2017
ORDINARY EXAMINATION FOR THE DEGREES OF BACHELOR OF
SCIENCE IN INFORMATION TECHNOLOGY
BIT2303 & BBIT 305 DISTRIBUTED SYSTEMS
FULLTIME/PART TIME/DISTANCE LEARNING
DATE: AUGUST, 2017 TIME: 2 HOURS
INSTRUCTIONS: Answer Question One & ANY OTHER TWO questions.
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 (6 Marks)
i. Location transparency
ii. Migration transparency
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) Differentiae 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)
