Question

Host A and B are communicating over a TCP connection. The initial sequence number at Host A is 2171. Host A opens the connection, sends three segments, the second of which carries 400 bytes of data, and closes the connection. In the segment sent by Host A, source port number is 303, and the destination port number is 80.

) What is the value of the sequence number of the SYN segment? (1.5 marks) )

What is the value of the sequence number of the data segment? in the acknowledgment of the second segment,what is the acknowledgment number, the source port number, and the destination port number?

) What is the value of the sequence number of the FIN segment? (1.5 marks)

Answer 1

Hello,

TCP 3 way handshake in TCP/IP process is a set for process for communication, between client-server or host-Host.

1. SYN is used to initiate a connection.
2. ACK is an acknowledgement that other side has received the SYN
3. SYN-ACK is the SYN bit from the sender with the acknowledgment of the earlier data.
4. FIN is for terminating the connection

• What is the value of the sequence number of the SYN segment?

While beginning the communication, as an initial step the connection needs to be established. The Host A will send a SYN segment with a sequence number and informs the Host B about the communication to be made. This sequence number indicate the initial sequence number of the data that will be transferred.

So, the Value of the sequence number of the SYN segment is 2171

• What is the value of the sequence number of the data segment? in the acknowledgment of the second segment, what is the acknowledgment number, the source port number, and the destination port number? (3 marks)

Now second segment sends 400 bytes of data – new sequence number= 2171+400 = 2571

The acknowledgement of the second data segment will be the received sequence number incremented by 1 = 2572

The source port number is 80 and the destination port number is 303

• What is the value of the sequence number of the FIN segment? (1.5 marks)

FIN segment is used to terminate the connection, which carries no sequence number.

The FIN segment can be sent with the last data segment transferred.