Transmission Control Protocol (TCP)

Control Flags

1. Start Wireshark to capture packets when your browser connects to a WWW server.
2. Identify the packets for the "3-way handshaking" of TCP, and what "flags" are set in these packets.
3. Identify the packets for the "4-way teardown" of TCP, and what "flags" are set in these packets.
4. Which host initiate the teardown process?
5. Can you find an example where teardown is initiated from the other side?
6. Observe the flags in all the packets which you captured. In addition to SYN, ACK, FIN, is there any other flag set? Explain why these are necessary in TCP applications.

Acknowledge Number

1. From the above packets, trace how Sequence Number and Acknowledgment Number increase. Make sure you know how to calculate the new Sequence Number and Acknowledgment Number from the above packet.
2. Download a file via FTP. Observe the TCP segment length of FTP data. Is the PUSH flag set?

NDT

1. Visit Google Measurement Lab. Run "Network Diagnostic Test", and see the results in "Details" and "Advanced".