In the network shown below, frames are generated at Node A and sent to Node C th

Question

In the network shown below, frames are generated at Node A and sent to Node C through Node B. Nodes B and C acknowledge each data frame immediately upon receipt to Nodes A and B, respectively. The channel data rate between Nodes A and B is 256 kbps and the data rate between nodes B and C is 1 Mbps. The lines between each pair of nodes are full-duplex, and the propagation delay for each line is 10 msec/mile. All data frames are 1000 bits long and ACKs are separate frames of negligible length. A sliding window protocol with a window size of W is used between Nodes A and B, and a stop-and-wait protocol is used between Nodes B and C. All lines are error-free and no frames can be lost.

1) What is the maximum window size Wmaxthat can be used between nodes A and B without flooding the buffers of node B?

Hint: The buffers of node B will not be flooded if the average number of frames entering and leaving Node B are equal over a long time interval (at steady-state).

Explanation / Answer

In order not to flood the buffers of B , the average number of frames entering and leaving B must be the same over a long internal .

A-> B Propogation time = 2000*10 = 20000 msec

Transmission time per frame = 1000/256 = 3.90 msec

B-> C Propogation time = 500*10 = 5000msec

Transmission time per frame = 1000/1000 = 1 msec

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