Medium access controller

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MAC or Medium Access Controller is the hardware or rarely software which provides data link layer connectivity for local area network protocols, most commonly Ethernet.

The MAC creates the Ethernet packets from the higher level network protocol packets. It adds a header containing the 6-byte destination Ethernet address, the 6-byte local host source Ethernet address, and a 2-byte packet type. It also adds a trailing 4-byte (32 bit) cyclic redundancy check, more commonly known as the CRC checksum, to the packet to guard against errors in the network.

The MAC address is the worldwide unique Ethernet address assigned to a particular Ethernet controller unit. Each individual Ethernet card or controller chip built into a computer system is supposed to have a unique 6-byte MAC address.

[edit] See also

• Ethernet
• OSI model
• MAC address
• Media Access Control