Bus and Ring topology uses Carrier Sense Multiple Access/Collision Detection (CSMA/CD).

CSMA/CD is a set of rules telling each network device when to transmit and when to stop transmitting data. When someone in the network wants to transmit something, it “listens” to the network at first in order to see if anyone else is using the channel. If no one else is transmitting, the device will go forward with its own transmission. if two devices follow the exact procedure at the exact same time, their transmissions will collide .

Carrier Sense/Multiple Access with Collision Avoidance (CSMA/CA): It is identical to CAMA/CD, but instead of sending the whole data chunk and then listening to hear if it was transmitted, the sender transmits a request to send (RTS) packet and waits for a clear to send (CTS) before sending. When it receives the CTS, the sender sends the chunk.