Computer Networking Concepts MAC MAC Medium Access Control

Computer Networking Concepts: MAC

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. 3 a, 802. 3 b, 802. 3 i, etc. .

MAC - Medium Access Control con’t

MAC - Medium Access Control con’t 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.

MAC - Medium Access Control con’t Preamble The Preamble is used to synchronize the receiving station's clock. It consists of 7 bytes of 1010. 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.

References Introduction to Data Communications Copyleft Sept. 1999 - Jan 2005 TCP/IP Tutorial and Technical Overview An IBM Redbooks publication Published 19 December 2006 Computer Networking: A Top-Down Approach (7 th Edition) James Kurose & Keith Ross