Media Access Control (MAC) is a sublayer of the Data Link Layer in the OSI model that determines how devices access and transmit data over a shared physical medium.
- The MAC sublayer ensures that data frames are sent without collision and controls device participation in data transmission.
Key Components of Media Access Control
1.) Contention-Based Access
In contention-based access methods, devices compete for the use of the shared communication medium.
- No centralized control.
- Suitable for low-traffic networks.
Example: CSMA/CD (Carrier Sense Multiple Access with Collision Detection) in Ethernet.
- Devices listen to the medium before sending data.
- If a collision occurs, devices wait for a random time before retrying.
2.) Controlled Access
In controlled access methods, a centralized or decentralized system ensures orderly access to the medium.
- Efficient in high-traffic networks.
- No collisions due to orderly access.
Types of Controlled Access:
- Polling: A central device (polling station) asks devices in turn whether they have data to send.
- Token Passing: A special “token” circulates in the network, and only the device with the token can transmit data.
