Assignment 1

1. HTTP Scenario
Use your web browser to connect to website of an Australian government department (www.****.gov.au). You must obtain a website from your tutor to ensure no students are using the same website. Using the Wireshark protocol analyser capture all HTTP packets related to, the request to and response from the Home page of the above website.
a. Include the Wireshark screen containing the first request HTTP packet. The packet number and the HTTP packet request line (including the host) should be clearly visible in the packet details pane.
(2 marks)
b. Find out the HTTP version number used by both client & server?
Which languages does the browser support?
When was the received webpage last updated?
(3 marks)
c. Both HTTP request & response header include a “Connection” field. It has a value of either “keep–alive” or “close”. Explain the purpose of this field, and meanings of keep–alive or close values. Also discuss if these values are relevant in the latest HTTP specifications.
(5marks)
d. Under an HTTP response header, check the field “Content-Encoding:gzip”. Explain what are meanings & advantages of using field.
[Note: you might not find Content-Encoding in an HTTP response message which is delivering an image. Look for it in a frame which contains textual data.]
(4 marks)
e. Capture and include the TCP packets that establish the connection to the web site using the three way handshake.
(2 marks)
f. Select an HTTP request‐response pair which transfers an image object. Calculate how many TCP transmissions it takes to download the object. Give the number of frames and size of the segments downloaded. What is the total size (in bytes) of the object downloaded?
(4 marks)
[Total 20 marks]
2. Email Scenario
Assume that:
 You have an email account at Monash domain (username@monash.edu.au)
 You use Mozilla Thunderbird client at Monash to send an email to Mike’s email address Mike.Smith@gmail.com.
 Mike is using web email to check his email and respond to your email.
 You use POP protocol to check Mike’s reply.
Given the above scenario, answer the following:
a. Illustrate in a single diagram:
i. The flow of packets between the computers involved. Include the following packet types (if required): SMTP, HTTP, IMAP, POP.
ii. Annotate all servers and client computers involved (e.g. MyPC, MikePC, etc.).
iii. Number the steps and related packets in the diagram.
(10 marks)
b. Give a brief step‐by‐step explanation of the flow of packets.
(5 marks)
[Total 15 marks]
3. Voice-over-IP (VoIP)
Use the Internet to search for information on the VoIP products Skype and Ekiga.
a. What application layer protocols does each product use?
(2 marks)
b. Compare and contrast them in terms of their capabilities and performance.
(8 marks)
[Total 10 marks]



4. Modulation Techniques
Draw a diagram to show how the bit pattern 1 0 1 1 0 0 1 0 would be sent using:
a. Two‐bit FM (i.e., four frequencies) (2 marks)
b. Two‐bit PM (i.e., four different phases) (2 marks)
c. Single‐bit AM combined with single‐bit PM (2 marks)
d. Two‐bit AM combined with two‐bit PM. (4 marks)
e. Digital 16-QAM (read Wikipedia), compare with (d) above. (5 marks)
[Total 15 marks]
5. The Address Resolution Protocol (ARP)
Describe ARP and answer the following questions:
a. Why is this protocol needed? (1 mark)
b. At what layer of OSI Model does ARP operate? (1 mark)
c. Compare ARP request and reply messages. (4 marks)
d. Describe the ARP poisoning attack. (2 marks)
e. Describe the ARP proxy feature. (2 marks)
[Total 10 marks]
6. Forward Error Correction (FEC)

Very useful link for converting HEXADECIMAL to BINARY

Convert numbers

Answer the following questions:
a. Define FEC, and list three attributes of it.
(3 marks)
b. Suppose data of 4 bytes is to be sent over a network. Calculate and compare the overhead in bits using the Hamming Single-Bit Code versus using the 1 bit Parity Check.
(3 marks)
c. Suppose the hexadecimal representation of the 4 bytes of data is
0x1F351A02:
i. Determine the codeword for this data
ii. The codeword is transmitted and received at the destination with its data corrupted to 0x1F351B02. Show how this can be detected and fixed at the destination using the Hamming Single-Bit Code.
(4 marks)
[Total 10 marks]
7. Technical Report
The company you work for wants to purchase broadband capability for its 20 staff members, so that they can access the office systems from home. You have been assigned the task of contacting telecommunications service suppliers to compare their offerings, in terms of technical capability and cost. You are required to write a technical report that compares ADSL2+ services versus Cable modem services. Select two service suppliers and compare their offerings, determine which service supplier offers the best solution.
a. Technical Capability
In tabular form compare the following:
 Service Supplier
 Device
 Modulation type
 Modulation bit rates achievable
 What error control strategy is used if any?
 Is the modulation sensitive to crosstalk?
 What cable and connector types are required for the line interface?
 What host side interfaces are provided? (Hint: Ethernet, Firewire, USB3)
 How many ports are provided?
 What protocol support is provided (i.e. PPP or other)?
 The protocol transmission efficiency of uploading a 20Mbyte file.
(10 marks)
b. Service Costs Comparison
Compare the service costs — e.g. installation, ongoing maintenance, technical support, warranty, leasing, purchasing etc.
(6 marks)
c. Recommendation
Which service do you recommend? Justify your answer.
(4 marks)
Note: Report word count should be in range of 600 to 1000 words.
[Total 20 marks]

PSK Modulation Diagram link