A Token Ring is a local area network in which computers are connected to each other using ring or star topology. A token is a frame which is used in these topologies in order to avoid collisions of data when two computers want to send information simultaneously. The Token ring resides on the data link layer of OSI model.
The token circulates in a loop, this means that the token reaches to each and every computer sequentially.
Here is how it works:
- A blank or empty token circulates on the ring.
- When a computer wants to send a message, it removes the blank token from the ring and places a new token which contains the message and the address of the destination computer.
- This token is analyzed my each and every computer in the ring sequentially(in order they are connected).
- The workstation which matches the address within the token, extracts the message from the token and changes the value of the token to 0.
- The token starts circulating again until the source workstation (originator) receives the token with the value 0, which indicates that the message has been reached successfully.
- And lastly, a blank token is placed on the ring so other computers can transmit.
This token-passing is a great scheme, because it avoids collisions, which is done by circulating a single token in the ring. This way only one computer will be able to gain access to the token and transmit at a time.