Turn in this exercise by e-mailing to email@example.com your answers to the questions below.
You may do this assignment in groups of up to three.
This assignment asks you to study TCP connection management.
Start wireshark, using appropriate filters for the task below.
After starting wireshark, visit a web page with your browser.
Inspect the TCP header sent by your browser in the SYN packet.
Inspect the TCP header sent by your browser in later packets.
Find the FIN packets exchanged by client and server.
Write a client that sends an HTTP request -- you may base your code on the assignment 2 of anyone in the class.
Modify your code to close the connection immediately after sending the request header.
Modify your code from the previous part so your client sleeps for a long time after sending the request.
While your client is sleeping, stop it with ^C (control-C) from the terminal, or with the kill command (run ps first to find the process ID).
Figure out what you can do to observe a reset connection in wireshark. Do it, then
Note that wireshark gives you relative sequence and ack numbers. To obtain the absolute sequence (ack) number, highlight the sequence (ack) number field in the middle wireshark window, and copy the corresponding four bytes (in hex).
Also note that the middle window in wireshark will not show an ACK field for the SYN packet. The ack value is the 4 bytes following the 4 bytes of the sequence number.
In wireshark, capture a TCP exchange that sends many bytes (several megabytes or more). Stop the capture, and under the Statistics menu, select "TCP Stream Graph", and "Time-Sequence Graph (tcptrace)".
You should see two lines. The lower line represents the sequence numbers sent by the data sender, while the upper line represents the ack numbers sent back by the receiver.
You can zoom in to the graph by clicking and dragging the left mouse button around the area of interest. You can zoom out with "-".
I encourage you to explore the other available tools as well.
Computer Networks, ICS 451
Instructor: Edo Biagioni