91Ó°ÊÓ

Exercises are given fractional (floating point) numbers, to allow for interpolation of new exercises. Exercise 4.5 is distinct, for example, from exercises 4.0 and 5.0. Simultaneous connection initiations are rare, but simultaneous connection termination is relatively common. How do two TCP nodes negotiate the simultaneous sending of FIN packets to one another? Draw the ladder diagram, and label the states on each side. Which node goes into TIMEWAIT state? Hint: there should be two pairs of crossing packets

Suppose A and B create a TCP connection with ISN =20,000 and ISN =5,000. A sends three 1000-byte packets (Data1, Data2 and Data3 below), and B ACKs each. Then B sends a 1000-byte packet DataB to A and terminates the connection with a FIN. In the table below, fill in the SEQ and ACK fields for each packet shown.