Question

Assume that two nodes A and B are on the same segment of 10Mbps Ethernet. The propagation delay between the two nodes is 200 bits time( time to transmit 200 bits of data) .At time t=0, A begins transmitting a frame of 800 bits. Before A finishes , B begins to transmit . Can A surely detect a collision before finishing transmitting ? Hint: consider worst case for a possible collision when B can start transmitting.

b) in the above problem , if A and B are connected via switch .Is collision possible A and B start transmitting at the same time ? Why or why not ?

Answer 1

a)

Worst case possible time is 2*propagation delay which is also known as vulnerable time and which is

400/ 10, 0.04ms

so if B sends its data before 0.04 ms  then a collision detection is possible otherwise not

b)

Switch limits the collision domain to the node itself and so even if they send at the same time there won't be a collision