Two basic forms of MAC which are used in most of today´s LAN are:
- Token passing method used by the token ring and FDDI.
- CSMA/CD carrier sense multiple access with collision detection.
- Token passing method:
- In this method, a special frame called token is passed from one workstation to the other.
- Only the system which possess this token is allowed to transmit its data on the network.
- A workstation, after transmitting its data will release the token to the next workstation.
- This method is used by the token ring and FDDI systems.
- CSMA/CD:
- The long form of CSMA/CD is carrier sense multiple access with collision detection.
- In this method when a workstation has to send some data, it listens to the network cable and if it is idle then sends the data.
- On CSMA/CD network the workstation can transmit simultaneously which results in packet collision.
- So this system has a collision detection mechanism. When a collision is detected, the corresponding data is retransmitted.
