In this lab, you will use the popular open-source packet analyzer Wireshark to analyze network traffic captured in a packet capture file provided to you. You will first get acquainted with basics of the Wireshark user interface, and then look at the packets in a capture file to understand how network communications take place.
You will write a lab report to describe your interactions with Wireshark. You will take screenshots and answer questions as indicated in this lab guide to demonstrate your understanding of the interface and the network traffic details.
Step 1: Explore the Wireshark Interface First, download the Wireshark installer and install it on your machine. Then, download the packet capture file CCA625WiresharkCapture.pcapng . Click on the file to open it in Wireshark. You will be presented with the Wireshark screen showing the file content. Take a screenshot of your open file and include it in your lab report.
The screen is composed of three parts. The top part shows the list of captured packets. Because network traffic on a busy machine involves lots of packets of various network protocols, Wireshark allows for two ways of packet filtering. Capture Filters are set up before capture and limit the body of packets captured.
Display Filters, which can be set up anytime in the filter toolbar on top of the screen, determine which of the captured packets are shown in the packet list. Packets in the packet list are color-coded depending on the protocol. The middle part of the Wireshark interface shows the detail of the packet selected in the packet list. The details are shown as a series of protocol headers as per the Open Systems Interconnection (OSI) model, starting from the physical frame and Ethernet data layers, through IP and TCP headers, to application layer protocols like HTTP and TLS (Transport Layer Security – a data encryption protocol).
You can expand each header to see the information contained in it. The bottom part contains the content of the selected package in hexadecimal and ASCII formats. Explore the Wireshark menus: Capture, Analyze, and Statistics. What are the Capture Options in the Input tab you can choose? Include the answer in your lab report.
Step 2: Inspect DNS Requests – Part 1 In the Display Filter bar under the main toolbar, type “dns”. The window turning green means the correct filter was entered.
Hit Enter or click on the horizontal arrow on the right end of the filter bar. The packet list will show only DNS packets. Take a screenshot and include it in your lab report. Take a look at the first DNS request. What is the IP address of the requesting computer? What is the IP address of the DNS server used by this computer? What site does this request look up? Include the answers in your lab report.
Step 3: Inspect DNS Responses In the packet detail window, scroll to the detail end. You will see the link to the packet, which is the response to this request. Click on it. The response packet detail shows up.
Take a screenshot and include it in your lab report. How many IP addresses are assigned to the site, and what are these IP addresses? What protocol is the DNS protocol implemented on top of? What is the port number used in that protocol? Try the following display filter: “.port==” where the protocol name and port number are taken from the answer to the previous question. What packet list is displayed with this filter? Include the answers to the questions in your lab report.
Step 4: Inspect DNS Requests – Part 2 Position the cursor in the filtered DNS packet list and click “File – Find Next.” In the search bar below the Display Filter bar, select “String” from the drop-down menu and type “mit”. What website does the DNS request found by the search? What is the IP address that was found? Take a screenshot and include it in your lab report. Include the answers to the questions in your lab report.
Step 5: Inspect HTTP Requests –Part 1 In the display filter bar, type “http” and select “http” from the drop-down menu. Apply the filter. Take a screenshot and include it in your lab report. Notice that the packet list contains packets of the HTTP protocol and its descendants in the protocol hierarchy. What protocol implemented on top of HTTP is used in this capture? Research this protocol on Internet and briefly describe what it is used for. Include the answers to the questions.
Step 6: Inspect HTTP Requests – Part 2 In the filtered HTTP packet list, find the first top-level HTTP packet (with HTTP in the protocol column).
What is the IP address of the request’s destination? What is the HTTP response code? Take a screenshot and include it in your lab report. Include the answers to the questions in your lab report.
Step 7: Inspect HTTP Requests – Part 3 Select packet #3512. What HTTP operation does this request invoke? What is its destination? Find the response to this request. What is the HTTP response code? What is the length of the returned data file? What is the extra header tucked on top of this response? Take a screenshot and include it in your lab report. Include the answers to the questions.
Step 8: Inspect IP Header Go back to packet #3512. In the packet detail pane, expand the Internet Protocol Version 4 header. What is the total length of the IP header? What is the request’s Time to Live? Take a screenshot and include it in your lab report. Include the answers to the questions.
Step 9: Inspect TCP Header In the packet detail pane of packet #3512, expand the Transmission Control Protocol header. What are the source and destination ports in the TCP header? What is the TCP sequence number for this request? What is the sliding window size? Take a screenshot and include it in your lab report. Include the answers to the questions.
Step 10: Inspect Packet Content Select the response to the request in packet #5312 in the packet list, and expand the HTTP header in the packet detail pane. Click on the last line in the request (“File Data”). In the packet content page, the file content is highlighted, showing in hexadecimal and ASCII formats. What kind of file is that? Take a screenshot and include it in your lab report. Include the answer to the question.
Step 11: Explore Capture Statistics Open Wireshark’s “Statistics” menu. In the Statistics menu, click on “Capture File Properties.”
What capture filters were used for this capture? In the Statistics menu, click on “Resolved Addresses.” How many domain names were resolved in this session? In the Statistics menu, click on “I/O Graph.” What does this graph show? In the Statistics menu, click on “Flow Graph.” What does this graph show? Take a screenshot of the last graph and include it in your lab report. Include the answers to the questions.
Step 12: Complete and Submit the Lab Report Write the report, showing steps you’ve taken, all requested screenshots, and answeiqurs to all questions from all steps.