Part $A(50\%{)}_{?}$

Question A$.1(20\%)$

There are four stations A$,$ B$,$ C and D in a bus network with the following data packets to be

transmitted. The packets and back$-$off information are given in the table below.

Assume the propagation delay is negligible and the source station can receive the acknowledgement

from the destination station immediately after the packet transmission. Further assume that there is no

other data in the network.

Clearly write down individual finish time for EACH packet and explain with a timing diagram.

Indicate with an $"x"$ where collision$($s$)$ has$/$have occurred.

a$)$ At what time will the packets successfully finish their transmissions if the network adopts non$-$

persistent CSMA protocol?

$(12\%)$

b$)$ At what time will the packets successfully finish their transmissions if the network adopts non$-$

persistent CSMA$/$CD protocol? Further assume that the station can detect packet collisions and

stop transmission within $3$ minutes after the beginning of transmission.

$(5\%)$

c$)$ Comparing your answers in a$)$ and b$),$ which protocol is more efficient in terms of packet

transmission time? Briefly explain.

$(3\%)$