MAC, Media Access Control

The media access control or MAC, is a sub-layer of layer 2 as specified in the seven-layer OSI (Open Systems Interconnection) model. It provides channel access control and addressing mechanisms that allow numerous terminals and nodes to interact within a multipoint network such as a LAN (local area network) or MAN (metropolitan area network). The mechanism used for addressing by the MAC layer is known as a physical address; more often referred to as a MAC address. This unique number is assigned to each network adapter, allowing packets of data to be delivered to multiple destinations within the subnetwork. A physical network may be connected by a hub, repeater, switch or a bridge but not a router. A good example of a physical network is Ethernet. The channel access control mechanism used in the MAC layer is often called multiple access protocol. This allows multiple interconnected stations to share the same physical medium. Some examples include ring networks, bus networks and wireless networks.