Definition: MAC layer

(Media Access Control layer) The part of the data link protocol that controls access to the physical transmission medium in local networks (see 802.3). The common MAC layer technologies are CSMA/CD for Ethernet and CSMA/CA for Wi-Fi. Earlier MAC layers were the token passing methods in Token Ring, FDDI and MAP.

MAC layer functionality is built into the network adapters, which includes a unique serial number that identifies the vendor and adapter (see OUI). See data link protocol, TCP/IP, OSI model, CSMA/CD, CSMA/CA and Ethernet.

The Bottom Layers

In IEEE 802 networks, the data link layer is split into two sublayers. The Logical Link Control (LLC) is an interface to the Media Access Control (MAC) layer. The MAC is also physical hardware, because the processes have been embedded into the transceiver chips. See IEEE 802, SNA, OSI model and Token Ring.