Lab 9-1: TCP Handshake and Connection Termination

• The red box encloses the three packets for a TCP handshake.

TCP Ports:

• Client/Browser TCP Port: 57387
• Server TCP Port: 80

SEQ/ACK Numbers:

• What is the initial Sequence # for communication from the Browser to the Server?: 1984097314
• What is the initial Sequence # for communication from the Server to the Browser?: 4143825931
• What is the Ack# indicating that the packet from Browser to Server was received? 1984097315
• What is the Ack# indicating that the packet from Server to Browser was received?: 4143825932

• The red box encloses the three packets for a graceful TCP termination.

Based on the Sequence and Ack #'s found in the FIN/ACK packets you included in your screenshot:

• How many bytes were sent from browser to server? Server to browser?
  • Both increase by 1 Byte when you do the typical calculations – however, this is a “phantom byte.” Acknowledge packets increase the sequence number by one even when data is not sent.
  • (4085806590 - 4085806591) = 1
  • (1104802490 - 1104802491) = 1

CORRECTION:

Based on the Sequence and Ack #'s found in the FIN/ACK packets you included in your screenshot: How many bytes were sent from browser to server? Server to browser?

• Browser to Server: 4085806590
• Server to Browser: 4085806591