Part 2

MAC Frame Format

The unit of transfer on the MAC sublayer is called a MAC frame.  The format differs for the various protocols. In general, the format is similar to the one in the picture.

• MAC Control: protocol control information (e,g. priority level)
• Destination MAC Address: the destination physical address
• Source MAC Address: the source physical address
• LLC: the LLC data
• CRC: the cyclic redundancy check (of FCS - frame check sequence)

In most data link control protocols, the DLC is responsible for detecting and recovering from errors. These two functions are split between the MAC and LLC layers. The MAC layers detects and discards any frames that are in error. Optionally, the LLC keeps track of which frames have been received and retransmits missing frames,

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