Many LAN methods that are ring topology need token passing for synchronized access to the ring. The ring itself is acts as a single shared communication phase. Both pass from transmitter passed by other devices and are copied by destination.
Hardware have to be designed to pass token ever if attached device powered down. This is given in figure below
USING THE TOKEN:
When a device waits to transfer it waits a token. After transmission device transmits token on ring. Next device is then ready to send, receive and then transmits.
TOKEN AND SYNCHRONIZATION:
Because there is only one token, only one device will transmit at a time. Token is a short reserved frame that may not seem in data.
Hardware must recreate token if lost. Token produce computer permission to send one packet frame. If all devices are ready to transmit it enforces Round-Robin process. But if now device is ready to transmit, token circulates in whole ring.
IBM TOKEN RING:
It is very commonly used. It was usually 4Mbps and now it is upto 16Mbps. It needs special connection cable between the device and the Ring interface.