QUESTION #$3(20$ points, $10$ minutes$)$

In the figure below, frames $($packets$)$ are generated at node A and sent to node $C$ and $D$ through node $B.$ Nodes

A and $B,$ as well as $B$ and $C$ and $B$ and $D$ are directly connected. For flow$-$control between A and B$,$ B and C$,$

and $B$ and $D,$ point$-$to$-$point flow control is performed but no end$-$to$-$end flow control. Determine the sliding

window size so that the buffer at node B will not over flow, based on the following conditions:

The data rate between A and $B$ is $400Mbps(M={10}^6)$

The data rate between B and C$,$ and B and D is $200$ Mbps $($for each$)$

The propagation delay is $20s,10s$ and $10s$ for link A$-$B$,$ B$-$C$,$ and B$-$D respectively.

The links are all full$-$duplex links.

All data frames are $800$ bits long; ACK messages are separate frames of negligible length $($frame

transmission delay $=0).$

For link A$-$B$,$ selective$-$reject ARQ is used.

For link B$-$C and B$-$D$,$ stop$-$and$-$wait ARQ is used.

The frame error rate is $P$ for all the three links.

Note: You do no have to complete your calculation. Develop an equation that calculates the required window

size and set up all the parameters in your equation.