Consider two active nodes A and B on an ethernet with lots o

Consider two active nodes, A and B, on an ethernet with lots of frames to send. Each node tries to send its first frame and they collide, send their jamming signal and calculate a back-off time in the interval [0,1] slots. Let A be the node that chooses a back-off time 0 and B chooses a back-off time of 1 slot (if both pick the same slot, they collide again). So A sends its first frame successfully and B decides to wait 1 slot. However during the next time slot when B tries to send its first frame, A also tries to send its second frame, so they collide again. Answer the following questions:

(a) After the last collision (A’s second frame colliding with B’s first frame), what are the back-off intervals nodes A and B are choosing from?
(b) What is the probability that B wins over A and can send its first frame successfully?
(c) If A wins that round, do you think that B has a fair chance to win the next round? Explain why.

Solution

(a) A will choose time slot as 0 and B will choose time slot 0. As both will choose their second from interval [0,1]

(b) 0 as frames will keep on colliding