A characteristic common to all Local Area Networks is that multiple hosts have to share access to a single physical transmission medium. Several methods can be employed to control the sharing of access to the transmission medium. The various access control methods can be characterized by where in the network the transmission control function is performed. An access method can use following forms of transmission control:
1. Random control
With random control any host can transmit and permission is not required. A host may
check the medium to see if it is free before beginning to transmit.
2. Distributed control
With distributed control only one host at a time has the right to transmit and that right is
passed from host to host. This is usually done by passing on a small piece of data called a
token. The host that has the token, is the one that has the right to transmit.