Consider two nodes A and B onashared $25$ MbpsCSMA$/$CDchannel$.$ A and B each have two

$800-$byte frames to send. Ignore propagation delay and assume that any existing

transmission from one node can be immediately detected by the other. Suppose both nodes

begin transmitting their first frame at time t $=0,$ and then collision occurs and both nodes

back off. The CSMA$/$CD protocol at A and B follows the following conventions: A $($or B$)$ will

immediately abort its transmission as soon as a collision is detected. After failure of an

attempt to send a frame, A will attempt to retransmit after waiting $396$K bit times, where K is

chosen each time by exactly following the sequence of $\{1,2,3,4,5,...\},$ i$.$e$.,$ K $=1$ is used

when the first attempt to send frame x $($x$=1,2)$ fails, K $=2$ is used when the second attempt

to send frame x $($x$=1,2)$ fails, and so on$.$ Similarly, B will attempt to retransmit a frame after

waiting $512$K bit times, where K is chosen each time by exactly following the sequence of $\{1,$

$2,3,4,5,...\}.$ A $($or B$)$ will attempt to send the second frame $900$ bit time after the first

frame is successfully sent.

$(1)$ When will B start the successful transmission of its first frame?

$(2)$ When will A start the successful transmission of its second frame?

$(3)$ Let T be the time when both A and Bhavecompleted the successful transmission of their

respective two frames. Calculate the efficiency of the CSMA$/$CD channel during the time

interval $[0,$ T$](20$ marks$)[$Multiple Access $($Learning Outcomes $2,3)]$

Consider two nodes A and $B$ on a shared $25Mbps$ CSMA$/$CD channel. A and $B$ each have two

$800-$byte frames to send. Ignore propagation delay and assume that any existing

transmission from one node can be immediately detected by the other. Suppose both nodes

begin transmitting their first frame at time $t=0,$ and then collision occurs and both nodes

back off. The CSMA$/$CD protocol at A and B follows the following conventions: A $($or $B)$ will

immediately abort its transmission as soon as a collision is detected. After failure of an

attempt to send a frame, A will attempt to retransmit after waiting $396K$ bit times, where $K$ is

chosen each time by exactly following the sequence of $..$ i$.$e$.,K=1$ is used

when the first attempt to send frame $x(x=1,2)$ fails, $K=2$ is used when the second attempt

to send frame $x(x=1,2)$ fails, and so on$.$ Similarly, B will attempt to retransmit a frame after

waiting $512K$ bit times, where $K$ is chosen each time by exactly following the sequence of $,$

$2,3,4,5,$dots.$\mathrm{.}3.$ A $($or B$)$ will attempt to send the second frame $900$ bit time after the first

frame is successfully sent.

$(1)$ When will B start the successful transmission of its first frame?

$(2)$ When will A start the successful transmission of its second frame?

$(3)$ Let $T$ be the time when both A and $B$ have completed the successful transmission of their

respective two frames. Calculate the efficiency of the CSMA$/$CD channel during the time

interval $0,T.$