back off algo

Question

Assume X and Y are the only two stations on ethernet.Each has a steady queue of frames to send.Both X and Y attempt to tranmit a frame,they wait to get the control of the channel using binary exponential algo.The prob that both were successfully allowed to send the frame on 5th round(assuming everytime both X and Y will collide in back off race till 4th round)

Comments

and also without knowing on collision whether X or Y wins...how will we use back off?

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According to the given question, the stations collide till the 4th round and they will be choosing the numbers from the same number space, so till the 4th round, we just need to consider the cases where collision happens and in the 5th round, we take the complement of the collision cases' probability.

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tanku @sukanya