Date: 31-07-03

Lecture Number: 03

Author: Arati Kadav

MAC:Medium Access Control

During transmission if more than one node access the same medium, collision occurs. Different protocols are used by nodes to avert these collisions.

MAC in Ethernet (Wired medium)

The Protocol used in MAC layer of the ethernet is CSMA/CD (Carrier Sense Medium Access with collision detection). It is contention based protocol meaning the nodes are allowed to contend for the same medium.
CS part of CSMA : Carrier Sense : Senses whether any transmission is going on. If not it transmits packet and listen at the same time.
CD part of CSMA/CD: Collision Detection : There are comparators with each node that take in both the sent and received signal at the same time. These comaparators compare the electric signal and both the sender and receiver's end and any discrepency is reported as collision.