The Function of Access Controls
The set of rules that determines how a computer should put data onto the network cable and also how data is taken off the cable is called an access method. Access methods also assist in regulating the flow of network traffic.
The computers on the network must share access to a common cable that connects them. If two computers were allowed to transmit at the same time then a collision will occur resulting in the data from both machines being destroyed. In order to detect or avoid this, a method for accessing the media must be used.
Access methods must be consistent in the way they handle data. If a situation arose where different computers were using different access methods, then the network would fail because some methods may well dominate the cable. Access methods must prevent computers from achieving simultaneous access to the cable.