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Distributed Systems Question Paper

Distributed Systems

Course:Bachelor Of Science In Information Technology

Institution: Kca University question papers

Exam Year:2010

UNIVERSITY EXAMINATIONS: 2009/2010
FIRST YEAR EXAMINATION FOR THE DEGREE OF BACHELOR OF
SCIENCE IN INFORMATION TECHNOLOGY
BIT 2303: DISTRIBUTED SYSTEMS
DATE: APRIL 2010 TIME: 2 HOURS
INSTRUCTIONS: Answer question ONE and any other TWO questions
QUESTION ONE
a) List and describe the two semantics of synchronisation used in distributed systems
communication (6 Marks)
b) Using a diagram describe the structure of a directory service name space (6 Marks)
c) Replication protocol can be described using five generic phases. Analyze the contribution of each phase (10 Marks)
d) Explaining the concept of the term ‘remote method invocation (RMI)’ (2 Marks)
e) Briefly explain the meaning of each of the following terms. Give one example for term
i) Distributed system (2 Marks)
ii) Transparency (2 Marks)
iii) Middle ware (2 Marks)
QUESTION TWO
a. RPC and RMI are normally used to provide transparency in a distributed system. However
they pose some dangers to the system. Explain some of the problems that can be
encountered in a distributed system due these techniques (4 Marks)
b. State any four types of transparencies (4 Marks)
c. Using illustration discuss the following models of client server systems highlighting the characteristics of scalability, flexibility and reliability
i. Vertical Distribution (Multi-Tier) (6 Marks)
ii. Horizontal Distribution (6 Marks)
QUESTION THREE
a) Explain why the following systems are distributed systems
i) The Web (2 Marks)
ii) Civil Aviation (2 Marks)
iii) Peer-to-Peer (P2P) files sharing networks (2 Marks)
iv) Bank ATMs (2 Marks)
b) Transparency is used to achieve various concepts in a distributed system. Outline the three major questions that you need to ask before implementing various transparencies (3 Marks)
c) Using an illustration briefly, explain the various layers in a distributed system (4 Marks)
d) Using examples differentiate between the following fault tolerance concepts
i) Fail (1 Mark)
ii)Error (1 Mark)
iii) Fault (1 Mark)
iv) Crash failure (1 Mark)
v) Omission failure (1 Mark)
QUESTION FOUR
a) The lifetime of a socket between a server and a client can be described by the following steps:
i) Binding
ii) Connection
iii) Data transfer
iv) Discard
Describe how the socket primitives in client server architecture are used to implement the steps listed above (10 Marks)
b) Outline the purposes of interprocess communication in a distributed system (5 Marks)
c) Explain with examples three reasons for organizing name servers hierarchically (3 Marks)
d) Why are the Distributed Systems inherently insecure? (2 Marks)
QUESTION FIVE
a) In passive replication one of the replication servers is elected incase of failure of the primary server. Describe the election algorithms used to facilitate the election process (10 Marks)
b) In distributed systems, there are many components intereacting together. Distributed
transactions execute in all or some of the components. Describe fully using a state transition diagram how the two phase commit technique is used to control transactions (10 Marks)

Distributed Systems Question Paper

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