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Cisy 432:Distributed Systems Question Paper
Cisy 432:Distributed Systems
Course:Computer Science
Institution: Kenya Methodist University question papers
Exam Year:2015
END OF 1''st ''TRIMESTER 2015 (PT) EXAMINATION
FACULTY : COMPUTING & INFORMATICS
DEPARTMENT : COMPUTER SCIENCE
UNIT CODE : CISY 432/BBIT 448/COMP 443
UNIT TITLE : DISTRIBUTED SYSTEMS
TIME : 2 HOURS
INSTRUCTIONS:
Answer question One and any other two questions
Question One (30 marks)
What is a distributed system?
(2 marks)
Why is it difficult to synchronize things in distributed systems?
(1 mark)
Scalability can be achieved by applying different techniques. What are these techniques?
(4 marks)
What is redundancy and why is it used in a distributed system? (2 marks)
With examples, explain the difference between iterative name resolution and recursive name resolution.
(2 marks)
Explain with examples the difference between a name server and a directory server.
(2 marks)
When passing data values between different machines with different operating systems what problems have to be solved?
(2 marks)
What is strict consistency and why is it not possible to achieve in a distributed system?
(3 marks)
Explain what problems can happen if there is no concurrency control where multiple transactions are being executed at the same time.
(2 marks)
What is the role of middle wave in a distributed system?
(2 marks)
Why is it not always a good idea to aim at implementing the highest degree of transparency possible?
(2 marks)
In message-based communication systems, what are the differences between persistent messaging and transient messaging
(4 marks)
Question Two (20 marks)
Two requirements of the Domain Name System (DNS) are (i) to scale to large numbers of computers, and (2) to allow organizations to administer their own naming systems. How does DNS achieve these two goals?
(6 marks)
The two types of transport services that the internet provides to its applications are TCP and UDP. Discuss the four main characteristics that separate these services.
(6 marks)
Explain in detail the Bully algorithm for electing a leader as used in clock synchronization.
(4 marks)
Briefly describe by use of diagrams the following architectural styles as used in implementation of distributed systems.
(4 marks)
Question Three (20 marks)
What are client and server stubs and how are they used in remote procedure calls? Explain in detail how remote procedure call is executed.
(8 marks)
With the aid of a diagram, describe what three tiered client-server architecture is.
(4 marks)
What is the difference between a vertical distribution and a horizontal distribution
(4 marks)
Compare reaching a file using a single-threaded file server and a multithreaded server. It takes 15msec to get a request for work, dispatch it, and do the rest of the necessary processing, assuming that the data needed are in a cache in main memory. If a disk operation is needed, as is the case one-third of the time, and additional75msec is required, during which time the thread sleeps. How many requests/sec can the server handle if
It is single threaded
It is multithreaded
(4 marks)
Question Four (20 marks)
Give advantages and disadvantages of constructing a concurrent server by spanning a process as compared to multithreaded servers.
(5 marks)
Distinguish between peer-to-peer and client server distributed system architectures.
(5 marks)
Outline the main feature of a grid computing system that distinguishes it from a general cluster computing system.
(5 marks)
Define the following concepts and explain how they influence the give application developer.
(5 marks)
Heterogeneity, for a web service designer(e.g. email, video service)
Openness, for a peer-to-peer file sharing system designer.
Scalability for a name service designer (e.g. DOI, DNS)
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