CSMA/CD and CSMA/CA
CSMA/CD: Carrier Sense Multiple Access with Collision Detection. Used in wired Ethernet bus topologies, including a hub. A technology defined by the Ethernet IEEE 802.3 committee. Each device senses the cable for a digital signal before transmitting. Also, CSMA/CD allows all devices on the network to share the same cable, but one at a time. If two devices transmit at the same time, a frame collision will occur and a jamming pattern will be sent; the devices will stop transmitting, wait a predetermined time as well as a self-imposed random amount of time, and then try to transmit again.
CSMA/CA: Carrier Sense Multiple Access with Collision Avoidance. Used in wireless Ethernet networks. A transmission technology that attempts to avoid collisions rather than detect them as in CSMA/CD. Used in wireless Ethernet (802.11) and Apple’s LocalTalk, when a device needs to transmit, it listens to the network (senses the carrier) and waits for it to be free. In 802.11, it then waits a random period of time and transmits. If the receiver gets the frame intact, it sends back an ACK to the sender.
Great YouTube video here.
