The underlayer Media Access Control or MAC is, according to the standards of data-processing networks IEEE 802. X , the lower part of Course binder of data in OSI model. It is used as interface between the software part controlling the connection of a node (Logical Link Control) and the physical Layer (material). Consequently, it is different according to the physical type of media used (Ethernet, Token Ring, WLAN,…)

The MAC underlayer deals mainly with:

• to recognize the beginning and the end of the screen S in the binary flow received of the physical Layer;
• to delimit the screens sent while inserting information (like additional bits) in or between those, so that their recipient can determine the beginning and the end of it;
• to detect the errors of transmission, for example using a Checksum (checksum) inserted by the transmitter and checked by the receiver;
• to insert the addresses MAC of source and destination in each transmitted screen;
• to filter the screens received by keeping only those which are intended to him, by checking to them Adresse MAC of destination;
• to control the access to the physical media when this one is divided.

A Adresse MAC is a succession of 6 Octet S (often represented in the hexadecimal form 01:23: 45: 67: 89: ab) which characterizes thus each Interface network.

See too

• Course binder
• Logical Link Control
• Address MAC
• Ethernet (IEEE 802.3)
• Token Ring (IEEE 802.5)
• WiFi (IEEE 802.11)