How does token passing work

Akshay Singhal. Publisher Name. Time taken by a bit to complete one revolution of the ring is called as ring latency. Time taken by the token to complete one revolution of the ring is called as cycle time. Each station holds the token until its data packet reaches back to it. Each station releases the token immediately after putting its data packet on the ring.

There exists only one data packet on the ring at any given instance. The packet of data is then sent to machine 2 who reads the address, realizes it is not its own, so passes it on to machine 3. Machine 3 does the same and passes the Token on to machine 4. This time it is the correct address and so number 4 reads the message represented by the yellow flashing screen. It cannot, however, release a free Token on to the ring, it must first send the frame back to number 1 with an acknowledgement to say that it has received the data represented by the purple flashing screen.

The receipt is then sent to machine 5 who checks the address, realizes that it is not its own and so forwards it on to the next machine in the ring, number 6. Machine 6 does the same and forwards the data to number 1, who sent the original message. Machine 1 recognizes the address, reads the acknowledgement from number 4 represented by the purple flashing screen and then releases the free Token back on to the ring ready for the next machine to use. That's the basics of Token Ring and it shows how data is sent, received and acknowledged, but Token Ring also has a built in management and recovery system which makes it very fault tolerant.

Below is a brief outline of Token Ring's self maintenance system. Token Ring Self Maintenance When a Token Ring network starts up, the machines all take part in a negotiation to decide who will control the ring, or become the 'Active Monitor' to give it its proper title.

It offers excellent throughput under high-load conditions. It has built-in troubleshooting mechanisms such as beaconing and auto-reconfiguration and may now be used with UTP cabling. Few of the disadvantages of Token Ring are:. Token Ring is very expensive. All topology components cost much more than other more popular standards.

It is relatively proprietary.