What is Ring Topology?
In a ring topology, each node is connected to the two nearest nodes so that the entire network forms a circle, as shown in Figure . Data is transmitted clockwise, in one direction (uni directionally), around the ring. Each workstation accepts and responds to packets addressed to it, then forwards the other packets to the next workstation in the ring. Each workstation acts as a repeater for the transmission. The fact that all workstations participate in delivery makes the ring topology an active topology. This is one way a ring topology differs from a bus topology. A ring topology also differs in that it has no “ends” and data stops at its destination. In most ring networks, twisted pair or fiber-optic cabling is used as the physical medium.
How Ring Topology Works?
At the start, a free Token is circulating on the ring, this is a data frame which to all intents and purposes is an empty vessel for transporting data. To use the network, a machine first has to capture the free Token and replace the data with its own message.
In the example above, machine 1 wants to send some data to machine 4, so it first has to capture the free Token. It then writes its data and the recipient’s address onto the Token (represented by the yellow flashing screen).
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 message 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.
Advantages of Ring Topology
- High performance delivered
- Token ring technology reduces the need of server or central hub to manage the workstations
- All nodes have equal opportunity to transmit the data
Disadvantages of Bus Topology
- If one node is disrupted then the whole network goes down
- It becomes difficult to add/remove nodes
- If more than one token is generated then it may cause ambiguity in the sending of both kinds.
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