Transmission Control Protocol and Segment

Wireshark Lab: TCP
SOLUTION
Supplement to Computer Networking: A Top-Down
Approach, 6th ed., J.F. Kurose and K.W. Ross
© 2005-21012, J.F Kurose and K.W. Ross, All Rights Reserved

The answers below are based on the trace file tcp-ethereal-trace-1 in in http://gaia.cs.umass.edu/wireshark-labs/wireshark-traces.zip TCP Basics
Answer the following questions for the TCP segments:
1. What is the IP address and TCP port number used by your client computer
(source) to transfer the file to gaia.cs.umass.edu?
2. What is the IP address and port number used by gaia.cs.umass.edu to receive the file. Solution: Client computer (source)
IP address: 192.168.1.102
TCP port number: 1161
Destination computer: gaia.cs.umass.edu
IP address: 128.119.245.12
TCP port number: 80
3. If you did this problem on your own computer, you’ll have your own solution

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©2013 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

Figure 1: IP addresses and TCP port numbers of the client computer (source) and gaia.cs.umass.edu

4.

What is the sequence number of the TCP SYN segment that is used to initiate the
TCP connection between the client computer and gaia.cs.umass.edu? What is it in the segment that identifies the segment as a SYN segment?

Solution: Sequence number of the TCP SYN segment is used to initiate the TCP connection between the client computer and gaia.cs.umass.edu. The value is 0 in this trace. The SYN flag is set to 1 and it indicates that this segment is a SYN segment.

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©2013 Pearson Education, Inc. Upper Saddle River, NJ. All Rights Reserved.

Figure 2: Sequence number of the TCP SYN segment

5. 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? How did gaia.cs.umass.edu determine that value? What is it in the segment that identifies the segment as a
SYNACK segment?
Solution: