In the Open Systems Interconnection (OSI) communication reference model, media access management is performed by the Media Access Control (MAC) sublayer of the Data-Link Layer.
In an Ethernet network transmission, the function of media access management is to determine whether the transmission medium is free and available to send a frame. Media access management receives the frame from the Carrier Sense Multiple Access/Collision Detect (CSMA/CD) sublayer. It seeks to avoid collision with other traffic on the medium by monitoring the Carrier Sense Signal (CSNS) provided by the Physical Layer Signaling (PLS). Once media access management is satisfied that the transmission medium is available, transmission of the frame to the PLS can begin. If a collision does take place, media access management determines what action should be taken and when to try to send the frame again. Media access management is also responsible for checking a frame to determine its validity before passing it on to the data decapsulation function.