Introduction To Computing Lab #4 Kalyani Kaladi IT 104, 2DL 1 Objectives  In-Class Assignment   Wireshark TCP Home Assignment  Discussion Board # 4 2 Objectives- Wireshark TCP • Capture a packet on Wireshark • Examine the packet and answer questions • Time Sequence Graph 3 4 DESCRIPTION OF MAIN WINDOW •Title Bar: The title bar (like the one in any GUI) shows the title of the window, the closing, maximizing, and minimizing icons. •Menu Bar: The menu bar is made of several pulldown menus and tool bars used in most GUIs. We will using some of these menus in our lab assignments. •Filter Bar: The filter bar allows us to display packet we are interested in while hiding the rest. •Packet List Pane: The packet list pane displays a one-line summary for each captured packet. •Packet Detail Pane: The packet detail pane shows the detailed analysis for each frame. •Packet byte pane: The packet byte pane shows the entire current frame (selected in the packet list pane) in hexdump format (hexadecimal view of data) and ASCII format. •Status Bar: The last section of the window (at the bottom) is the status bar which shows the current protocol, the total number of packets captured, and so on. 5 Wireshark TCP Do the following: Start up your web browser. Go the http://gaia.cs.umass.edu/wireshark-labs/alice.txt and retrieve an ASCII copy of Alice in Wonderland. Store this file somewhere Next on your computer. (Right click and say save as on desktop) go to http://gaia.cs.umass.edu/wireshark-labs/TCP-wireshark-file1.html Use the Browse button in this form to enter the name of the file (full path name) on your computer containing Alice in Wonderland (or do so manually). Don’t yet press the “Upload alice.txt file” button. Now start up Wireshark and begin packet capture (Capture->Start (OR) Capture->Options->Ethernet/WiFi (whichever is active)->Start) and then press OK on the Wireshark Packet Capture Options screen (we’ll not need to select any options here). Returning to your browser, press the “Upload alice.txt file” button to upload the file to the gaia.cs.umass.edu server. Once the file has been uploaded, a short congratulations message will be displayed in your browser window. Stop Wireshark Take packet capture.(Capture->Stop) a screenshot of this and submit in the word document 6 Opening a captured packet  Go to http://gaia.cs.umass.edu/wireshark-labs/wireshark-traces.zip  Click on save to download the zip file  Unzip the file to retrieve the file traces  Go to Wireshark and click File->Open. Find tcp ethereal trace1 file in the unzipped folder.  The trace can now be viewed in the Wireshark window. 7 • Type in tcp in the filter and press enter. All tcp packets will show up. • You will observe a sequence of three messages SYN, SYN ACK, ACK. 8 Questions Based on Captured Packet 1. What is the IP address and TCP port number used by the client computer (source) that is transferring the file to gaia.cs.umass.edu? To answer this question, it’s probably easiest to select an HTTP message and explore the details of the TCP packet used to carry this HTTP message. 2. What is the IP address of gaia.cs.umass.edu? On what port number is it sending and receiving TCP segments for this connection? 3. What is the sequence number of the TCP SYN segment that is used to initiate TCP connection between the client computer and gaia.cs.umass.edu? 4. What is the sequence number of the SYNACK segment sent by gaia.cs.umass.edu to the client computer in reply to the SYN? What is the value of the ACKnowledgement field in the SYNACK segment? 5. Select a TCP segment that is being sent from the client to the gaia.cs.umass.edu server. Then select: Statistics->TCP Stream Graph->Round Trip Time Graph. 9
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