Media and Medium

MAC stands for "Media Access Control." This term encompasses all the tasks performed by the "Medium Access Controller." This is part of the network adapter. It translates digital data formatted for a computer into a format required by the network. It then converts that data into an electric signal and applies it to the cable of the network. Networks cannot handle more than one transmission at a time and so the Medium Access Controller has to listen for silence on the line before applying its signal. The same terms and process apply to wireless networks where the medium is radio waves and the controller transmits and receives this data with a radio transmitter/receiver.

Network Adapter

Every network adapter in the world has a unique serial number. This is used for the MAC address. Network adapters were originally manufactured as a separate piece of hardware printed on a board that slotted in to an expansion slot on the motherboard of a computer. They were originally called Network Interface Cards. Nowadays, computers ship with a network adapter integrated into the motherboard, yet the name Network Interface Card still persists as the more popular term for network adapters.

Format

A MAC address is a 48-bit binary number. This is six bytes. The first three bytes are an identifier code for the manufacturer of the network adapter. The second three bytes represent a unique serial number. The MAC address is represented as a 12-digit hexadecimal number and broken up into six sections by either a dash ("-") or a colon (":"). This results in a format like "12:34:56:78:90:ab."

IP Addressing

MAC addresses operate over one link of a network. To reach a far away computer, the network has to deal with IP addresses. IP addresses are used by routers, which carry data across several networks. MAC addresses are used by switches, which move data around a local area network. Data packets traveling outside the local area network will carry both a MAC address and an IP address.