Exercises on TCP exchange

SOLUTIONS.

1. In the following figure, find the values of a1, a2, a3, a4, b1, b2, b3, s1,s2, s3, s4, t1, t2, t3, TS1, TS2, TS3, TS4

2. In the above TCP exchange, which host will enter the TIME_WAIT period?

   The host that sent F first (one on the left in the figure)

3. What is the purpose of WINDOW size field in the TCP header?

   Flow control – To tell the other side how much we are prepared to receive at this time

4. Is there any problem if WINDOW size is set to a very high value?

   Large window tells the other side that we are prepared to accept large amounts of data. If the other side sends a lot of data at once, we, as well as the network, will be overwhelmed

5. List the differences between UDP and TCP header checksums

   UDP Checksum: Not Mandatory; uses 12-byte pseudo-header in calculations

   TCP Checksum: Mandatory; uses a 68-byte pseudo-header in calculations