Carrier-sense multiple access (CSMA) is a medium access control (MAC) protocol in which a node verifies the absence of other traffic before transmitting on a shared transmission medium, such as an electrical bus or a band of the electromagnetic spectrum.
Variations on basic CSMA include addition of collision-avoidance (CSMA/CA), collision-detection (CSMA/CD) and collision-resolution techniques.
Variations of CSMA use different algorithms to determine when to initiate transmission onto the shared medium.
A key distinguishing feature of these algorithms is how aggressive or persistent they are in initiating transmission.
A more aggressive algorithm may begin transmission more quickly and utilize a greater percentage of the available bandwidth of the medium.