Problem Solving Report

SIT202 Computer Networks
Trimester 2, 2017
Problem Solving Report 1
Due Date: 11:59pm Friday August 4
th
, 2017
This assessment task must be completed individually,
group work and/or collaboration with other students is prohibited.
All work completed/submitted as part of this assessment task must be your own, individual work.
Any content drawn from other materials, including unit materials, must be clearly quoted where
appropriate, and/or clearly referenced. All students should review and be familiar with the content
provided by the University regarding how to reference other materials:
http://www.deakin.edu.au/students/study-support/referencing
And in particular the information provided regarding Academy Integrity:
http://www.deakin.edu.au/students/study-support/referencing/academic-integrity
Unit Learning Outcomes
As per the Unit Guide, the following Unit Learning Outcomes are relevant to this project:
ULO 1. Demonstrate knowledge of concepts and roles of computer architecture and the influence
of different layers of communication protocols.
You will be required to demonstrate knowledge of concepts and the architecture of
computer networks including protocol layering, and services provided by layers.
ULO 2. Differentiate the types of networks, communication and user oriented protocols, and their
influence on transmission speed, reliable delivery and security.
You will be required to demonstrate knowledge of the different types of networks and
protocols and how they influence the various characteristics of networks for the
transmission of data between devices on a computer network.
Question 1 (Week 1) (10 + 12 = 22 marks)
a) Forouzan identifies one of the advantages of protocol layering as allowing intermediate
devices to be less complex by not requiring all layers (Section 2.1.1, pp34). Given that
modern routers, switches, and other intermediate devices often provide web interfaces for
administering/configuring the device:
i) Explain why all layers are required to be present for such devices; and
ii) Briefly discuss whether Forouzan’s identified advantage is still relevant.
b) In the Week 1 Class Slides in CloudDeakin, on page 49 is a figure illustrating the
encapsulation and decapsulation of data as it moves from source host to destination host.
The router is illustrated as having (i) two physical layers and (ii) two data link layers.
Explain why these are required and describe how they would be used when a datagram
passes through the router.
Hint: Consider that there are three basic phases of data passing through a router: data
arriving, processing by the router, and data outgoing.
Question 2 (Week 2) (14 + 15 = 29 marks)
a) Consider creating a new type of network where the network cable (copper) has a large
bandwidth and will be shared between several users.
i. Briefly describe how this network could be constructed either as a low-pass channel
using TDM, or as several bandpass channels using FDM.
ii. Identify one advantage and one disadvantage for each approach (note that it is
possible that an advantage for one approach could be a disadvantage of the other
approach).
b) You are employed by an organisation that stores and processes large volumes of highly
sensitive data. After moving to new premises (a new building), you discover that the wired
network between the data storage units and computation units is much higher latency
than previously. Your colleague suggests using an ad-hoc wireless network between the
two units will resolve the matter.
i. Briefly explain two potential problems with this approach.
ii. Considering each of the four components of latency (propagation time,
transmission time, queuing time, and processing delay), identify and explain one
possible cause and how to resolve it.
Question 3 (Week 3) (6 + 24 = 30 marks)
a) The ARP protocol is used to identify an Ethernet address for a given IP address and the
information discovered using this protocol is temporarily kept by a device in its “ARP
cache”. Consider eliminating the ARP protocol by having devices periodically broadcast
their Ethernet and IP addresses instead, and explain the advantages and disadvantages of
this approach.
b) Referring to the Week 3 slides and training videos for examples of CRC and Internet
checksum calculations:
i. Demonstrate the generation of the CRC code for the following input:
Dataword: 1010 1100
Divisor: 1011
ii. Demonstrate the generation of the 16-bit Internet checksum for the following
input:
Dataword 1: 0011 0011 0011 0011
Dataword 2: 0110 1110 0110 1110
Dataword 3: 1000 0100 0010 0001
Question 4 (Week 1-3 Prac) (7 + 6 + 6 = 19 marks)
a) Consider configuring an IP address on a router and a switch.
i. Give an example of the commands used to configure an IP address on both a router
and a switch. Use your own IP address and subnet mask (do not re-use those that
appear on the practical task).
ii. Briefly explain why the switch’s IP address is not applied to a physical interface.
b) Briefly explain the problem with the telnet tool (Week 2 practical discussion question 5)
and identify an alternative tool and explain how it solves/eliminates this problem.
c) Briefly discuss the need for the IPCP protocol and describe what it is used for.
Marking Scheme
Question 1 (10 + 12 = 22 marks)
• Part (a-i)
o (5 marks) Explanation of why all layers are required to be present.
• Part (a-ii)
o (5 marks) Discussion of whether Forouzan’s identified advantage is still relevant.
• Part (b)
o (3 marks) Explanation of why two physical layers are required.
o (3 marks) Explanation of why two data link layers are required.
o (6 marks) Explanation of how separate physical and data link layers are used as a
datagram passes through the router.
Question 2 (14 + 15 = 29 marks)
• Part (a)
o (3 marks) Description of low-pass channel using TDM.
o (3 marks) Description of several bandpass channels using FDM.
o (2 marks) Advantage of low-pass and TDM.
o (2 marks) Advantage of several bandpass and FDM.
o (2 marks) Disadvantage of low-pass and TDM.
o (2 marks) Disadvantage of several bandpass and FDM.
• Part (b-i)
o (4 marks) Identification and explanation of first problem.
o (4 marks) Identification and explanation of second problem.
• Part (b-ii)
o (4 marks) Identification and explanation of possible cause
o (3 marks) Description of resolution to possible cause.
Question 3 (6 + 24 = 30 marks)
• Part (a)
o (3 marks) Explanation of advantages.
o (3 marks) Explanation of disadvantages.
• Part (b-i)
o (5 marks) Correct application of division.
o (3 marks) Correct quotient.
o (1 marks) Correct CRC code.
o (3 marks) General working.
• Part (b-ii)
o (3 marks) Correct application of addition.
o (3 marks) Correct demonstration of wrapping overflow bits.
o (2 marks) Correct checksum.
o (4 marks) General working.
Question 4 (7 + 6 + 6 = 19 marks)
• Part (a-i)
o (2 marks) Example of router commands.
o (2 marks) Example of switch commands.
• Part (a-ii)
o (3 marks) Explanation of why switch commands are applied to a virtual interface.
• Part (b)
o (3 marks) Explanation of problem with the telnet command.
o (3 marks) Explanation of alternative tool.
• Part (c)
o (3 marks) Explanation of the need for IPCP.
o (3 marks) Description of what IPCP is used for (what it does).

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