Category: Uncategorized

SIT202 Computer Networks
Trimester 2, 2017
Problem Solving Report 3
Due Date: 5pm Tuesday September 22
nd
, 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 3. Select a local area and design simple protocols for a given environment to track current
and future trends in computer networks.
Given current and future requirements for one or more networks, you will be required to
select/design appropriate protocols to satisfy those requirements.
ULO 4. Analyse and articulate security attacks and countermeasures, symmetric and public
cryptosystems, digital signature and authentication protocols.
You will be required to analyse one or more networks to explain the security requirements
of those networks and propose solutions.
Question 1 (Week 7) (14 marks)
Working for a software company you are attending a meeting to discuss the development of a
new application which will allow massive volumes of data to be transferred over several days.
One of the topics for discussion is whether the TCP or UDP protocol should be used. One of your
colleagues is convinced that TCP must be used as it provides services such as error control and
flow control which are critical for the data delivery task. Another colleague however points out
that the requirement for data transfer to occur over several days mandates the use of UDP, as
even a temporary network outage could cause the TCP connection to be dropped, in turn causing
the transfer to be aborted. In response, you tell them that they’re both wrong, and that either
protocol could be used. For both TCP and UDP:
i. Briefly explain how the protocol could successfully be used for this application;
ii. Briefly explain two advantages and two disadvantages of using the protocol for this
application.
Question 2 (Week 8) (17 marks)
Consider the operation of the SMTP protocol as illustrated in Week 8 Slide 59:
i. Briefly describe what is happening at each step of this exchange
ii. Briefly describe three services of the underlying transport layer and how they are
used/exploited by this application protocol.
iii. Briefly explain why this particular style of message exchanges and the formatting of the
email data section have been chosen for this application protocol.
Question 3 (Week 9) (16 marks)
Consider the Management Information Base proposed/defined for the TCP protocol in RFC4022:
https://tools.ietf.org/html/rfc4022
Briefly discuss what information you could learn about your network from the following objects:
• tcpAttemptFails
• tcpEstabResets
• tcpRetransSegs
• tcpConnectionTable
For each of the objects identified above:
i. Briefly describe what information the object contains (must be in your own words)
ii. Discuss what can be learned about what’s happening in the network on the basis of this
information, e.g., what would a low value versus a high value in object X potentially mean
is happening on the network?
Question 4 (Week 7-9 Prac) (9 + 4 + 6 = 19 marks)
a) Demonstrate the use of sequence numbers and acknowledgement numbers by the TCP
protocol to send a random short phrase which is divided into three segments, two of which
are delivered and acknowledged, before the final segment is delivered and acknowledged.
Note that only segment data content, sequence number, and acknowledgement numbers
are required.
Hint 1: Running a Google search for “short quotes” or similar will result in many short
phrases that could potentially be used (remember Code of Conduct rules apply, nothing
offensive/ abusive can be used).
Hint 2: A figure such as those prepared for Problem Solving Report 2 could help you to
answer this question!
b) In the Week 8 lab task, we examined the behaviour of the DNS protocol. Identify what
layer of the TCP/IP model the DNS protocol runs at and explain why.
c) In the Week 9 practical we examined the SNMP protocol (addressed in Question 3) and the
NetFlow protocols. Briefly describe what kind of information is provided by the NetFlow
protocol and briefly discuss what this information could be used for.
Submission Requirements
Please note the following requirements when submitting your answers:
• All questions and sub-questions must be clearly labelled and appear in the correct order,
e.g., Q1 before Q2, Qa before Qb, and so on. This is necessary to ensure your answers can
be found by the markers in a timely manner.
• Your answers must be submitted to the correct Assignment box provided in CloudDeakin,
submissions will not be accepted outside of this assignment box, e.g., email submissions
will not be accepted.
• Answers must be submitted in a format which can be read by the plagiarism detection
system. It is your responsibility to ensure your answers in a correct format.
o Acceptable formats include: Word (.doc/.docx), Excel (.xls/.xlsx), PowerPoint
(.ppt/.pptx), OpenOffice Text (.odt), Rich Text Format (.rtf), HTML (.html/.htm),
Acrobat (.pdf), and Text (.txt)
o Unacceptable formats include: ZIP/RAR/7z or any other type of archive,
submissions linked from the Portfolio (download the document from the portfolio
and upload it separately).
o Note that any diagrams you prepare as part of this Problem Solving Report can be
submitted either embedded in your document or separately using common image
formats
• Late submissions are penalised as per University regulations, which are based on the due
date of the submission. Note that the indication of lateness by CloudDeakin is often
misleading and not considered, lateness is determined comparing due date/time versus
submission date/time. For example, for a due date of 11:59pm Friday:
o Submission before Friday 11:59pm – no penalty.
o Submission after Friday 11:59pm but before Saturday 11:59pm – 5% penalty
o Submission after Saturday 11:59pm but before Sunday 11:59pm – 10% penalty
o Submission after Sunday 11:59pm but before Monday 11:59pm – 15% penalty
o Submission after Monday 11:59pm but before Tuesday 11:59pm – 20% penalty
o Submission after Tuesday 11:59pm but before Wednesday 11:59pm – 25% penalty
o Submission after Wednesday 11:59pm – not accepted.
• Applications for extensions can only be considered by the unit chair. In general,
applications must be submitted before the due date (unless it is not possible to do so), and
must satisfy the rules for special consideration, i.e., reasons must fall into categories for
medical, compassionate, or hardship, and evidence must be provided. If you have to wait
to receive evidence (such as documentation from a practitioner/professional), or if the due
date has passed, you should still contact the unit chair for advice as soon as possible.
Marking Scheme
Question 1 (14 marks)
• Part (i)
o (3 marks) Explanation of how TCP could be used for this application protocol.
o (3 marks) Explanation of how UDP could be used for this application protocol.
• Part (ii)
o (2 marks) Explanation of TCP advantages.
o (2 marks) Explanation of TCP disadvantages.
o (2 marks) Explanation of UDP advantages.
o (2 marks) Explanation of UDP disadvantages.
Question 2 (17 marks)
• Part (i)
o (5 marks) Description of each step of the illustrated exchange.
• Part (ii)
o (2 marks) Description of first service and how used.
o (2 marks) Description of second service and how used.
o (2 marks) Description of third service and how used.
• Part (iii)
o (3 marks) Explanation of why this particular style of message exchange is used.
o (3 marks) Explanation of why this particular formatting is used for the email data.
Question 3 (16 marks)
• Part (i)
o (4×2 marks) Description of what the object contains, per object.
• Part (ii)
o (4×2 marks) Discussion of what can be learned about the network, per object.
Question 4 (20 + 8 = 28 marks)
• Part (a)
o (6 marks) Demonstration of the data segments.
o (3 marks) Demonstration of the acknowledgements.
• Part (b)
o (1 marks) Correct identification of which TCP/IP layer DNS runs at.
o (3 marks) Explanation of why DNS is at the (correctly) identified layer.
• Part (c)
o (3 marks) Description of what kind of information is provided by NetFlow.
o (3 marks) Discussion of what this information could be used for.