Answer to Question #244447 in Computer Networks for Muhammad Ahsan

Question

TCP

Open the “tcp_packet_capture” trace file and find the first HTTP GET message from the trace with

packet length equal to 517 bytes and sequence number 2398008939. Hint: To limit yourself to TCP

messages, enter the string tcp in the filter field and then apply the filter. Answer the following

questions:

a. What are the IP address and TCP port number used by the client computer to retrieve

the file? [1]

b. What is the next sequence number of the TCP SYN segment? (Give the relative sequence

number). [2]

c. What is the flag field set to? [1]

d. Based on the value of the fields what flags are set in this TCP message?

Answer 1

As here tcp packet information is not attached so i am taking it random website and accessing it and capturing the data by the wire-shark.

a) From the given packet, we can see the highlighted terms are representing the port number and IP address of source and destination.

Source Address: 192.168.43.174

Destination Address: 54.192.166.142

Transmission control protocol (source port : 50075)

Destination port: 80

b)

From the image in (a) we can see the TCP Segment Length : 1

and Next Sequence Number: 2

c)

The flag is a set if the acknowledge number contains a valid acknowledge number.

d)

From the above diagram, we can see that the set flag is 0x010, congestion window reduced (CWR): not set, ECN-Echo