Introduction to Data Communications
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36f. MAC - Medium Access Control

The IEEE 802.3 Medium Access Control layer is physically located in the firmware (ROM) of the Network Interface Card. It is the link between the Data Link Layer and the Physical Layer of the OSI model and logically resides in the lower portion of the Data Link Layer. There is only 1 MAC layer for all IEEE 802.3 versions: 802.3, 802.3a, 802.3b, 802.3i, etc..

The IEEE 802.3 Medium Access Control uses CSMA/CD (Carrier Sense Multiple Access/Collision Detect) to determine Bus Arbitration. The MAC layer is concerned with the order of the bits and converting the Datagram from the Network Layer into Packets/Frames.

Preamble

The Preamble is used to synchronize the receiving station's clock. It consists of 7 bytes of 10101010.

Start Frame Delimiter (SFD)

The Start Frame Delimiter indicates the start of the frame. It consists of 1 byte of 10101011. It is an identical bit pattern to the preamble except for the last bit.

Start Frame Delimiter (SFD)

The Start Frame Delimiter indicates the start of the frame. It consists of 1 byte of 10101011. It is an identical bit pattern to the preamble except for the last bit.

Introduction to Data Communications
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