Question

In a TCP connection, the initial sequence number at the client site is 2171. The client opens the connection, sends three segments, the second of which carries 1000 bytes of data, and closes the connection. What is the value of the sequence number in each of the following segments sent by the client?

a. The SYN segment
b. The data segment
c. The FIN segment

Answer 1

The sequence number in the SYN segment is 2171, in the data segment it starts at 2172 and ends at 3172, and for the FIN segment, it is 3173.

Step-by-step explanation:

The initial sequence number at the client site in a TCP connection is 2171. Starting with the SYN segment, which is used to initiate the connection, the sequence number would still be 2171 since its primary role is to synchronize sequence numbers between the client and server.

Next is the data segment, in which the client sends 1000 bytes of data. Therefore, the sequence number for the data segment would be 2171 + 1 (for the SYN segment) = 2172. As each byte of data is accounted for, the sequence number for the end of the data segment would be 2172 + 1000 = 3172.

Finally, for the FIN segment used to close the connection, the sequence number would be the one immediately after the last data byte in the segment. So, the sequence number for the FIN segment would be 3172 + 1 (for the FIN itself) = 3173, assuming no more data was transmitted after the earlier data segment.