The University of Melbourne
COMP90015 Distributed Systems: Principles and
Paradigms
Semester 2, 2014 Final Examination
Department of Computing and Information Systems
COMP90015 Distributed Systems: Principles and Paradigms
Reading Time: 15 minutes
Writing Time: 3 hours
Open Book Status: Closed Book
This paper has 3 pages including this page
Identical Examination Papers: none
Common Content: none
Authorized Materials:
No materials are authorized.
Instructions to invigilators:
No papers may be taken from the exam room.
Instructions to students:
All answers are to be written in the script book(s) provided.
Attempt all questions – partial credit is available.
The examination is worth 60% of the subject assessment.
Paper to be held by Baillieu Library: no
1 of 3 continued on next page
COMP90015 Distributed Systems FINAL EXAMINATION
Q.1. (a) [1 marks] When considering the definition of a distributed system, a computer
network in unto itself is often not said to be a distributed system. Why is
this the case?
(b) [1 marks] What is the difference between availability and reliability?
(c) [3 marks] Instead of having an non-shared printer attached to each computer
in a computer network, a single printer can be used and shared among all of
the computers.
i. Is this an example of a distributed system? Explain.
ii. Explain a reason for, and a reason against this approach.
Q.2. [5 marks] List and briefly explain four general approaches to failure handling in
a distributed system. Give an example for each approach.
Q.3. (a) [4 marks] What is an architectural model? In your explanation include the
important aspects or steps when developing an architectural model.
(b) [4 marks] What is a fundamental model? In your explanation discuss three
aspects of distributed systems that are described using a fundamental model.
(c) [2 marks] Explain the following classes of failure:
i. Fail-stop
ii. Crash
iii. Omission
iv. Arbitrary
Q.4. [3 marks] Consider a server process that has a single TCP server socket, bound
and listening on port 4242.
(a) While listening for incoming TCP connections on port 4242, can the process
also receive UDP packets on port 4242?
(b) Assuming that each client is connecting from a different host, what operating
system aspect limits the number of concurrent client connections that the
server process can handle?
(c) Assuming the server process has 5 concurrently open connections from clients
how many ports does the server process require? Explain your answer.
(d) Is it possible for a client to connect from port 4242 to the server process?
Explain your answer.
Q.5. [2 marks] What is a benefit of XML over JSON format? What is a benefit of
JSON over XML format?
Q.6. [5 marks] Explain the exchange protocol used in the first project. Draw an inter-
action diagram and explain the messages that are sent. What was the purpose of
using a counter?
2 of 3 continued on next page
zzw
Highlight
zzw
Highlight
zzw
Highlight
COMP90015 Distributed Systems FINAL EXAMINATION
Q.7. (a) [2 marks] Discuss two advantages and two disadvantages of using high level
middleware (e.g. Java RMI middleware) compared to socket APIs in a dis-
tributed system.
(b) [4 marks] Describe the Tuple Space paradigm. Use a diagram and include a
description of the API used in a Tuple Space.
(c) [4 marks] Describe the Publish/Subscribe paradigm. Use a diagram and
include and include a description of the API used in a Publish/Subscribe
system.
Q.8. (a) [4 marks] Discuss centralized and decentralized architectures for distributed
load management. Critically compare them.
(b) [1 marks] Explain the difference between virtualization and emulation.
Q.9. (a) [3 marks] Explain what is a digital certificate and what is a certificate chain.
(b) [3 marks] Give three worst-case assumptions when designing a secure system.
Q.10. (a) [5 marks] Describe the caching policy used by NFS at the client. What
parameters are used? What checks are done, in what order and why?
(b) [2 marks] Explain how DNS can be used to distribute the load of incoming
requests over a set of servers.
(c) [1 marks] What is meant by pure name?
(d) [1 marks] What is meant by unification?
END OF EXAMINATION
3 of 3
zzw
Highlight
zzw
Highlight
zzw
Highlight
zzw
Highlight
zzw
Highlight