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Dated: Jun. 25, 2012
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Networking In General
Overview of Ring Topology
In ring topology, data used to transfer in the form of ring where every computer that was connected to the network had two LAN cards and each LAN card was connected to the LAN card of its neighbor computer. Many times ring topology was preferred over bus topology because there were no collisions and the chances of network getting congested were next to 0%.
When the concept of ring topology was invented, it was considered a foolproof topology because it was organized and arranged in such a way that the network traffic was never collided and the entire topology did not require additional devices like Terminators, as it was the case with bus topology. Moreover, ring topology was easily scalable as compared to bus topology as administrators just needed to disconnect one end of any computer and add a new computer by connecting both the ends of new computer to the disconnected cables.
How Ring Topology Worked
Since all the computers were connected to their neighbor computers, data in ring topology was transmitted from source computer to the destination in either clockwise or anticlockwise direction.
As soon as the very first computer of ring topology was powered on, it used to generate a token which used to circulate in the entire network. Irrespective of the need of data transmission of the computers, the token used to travel in the entire circle and was received and released by every computer that was connected. If any computer wanted to transmit the data to any other computer in the network, that computer used to hold the token. This process used to notify all other computers in the network that the computer who holds the token was about to transmit data. The computer holding the token then used to send the data on the wire and the data travelled according to the configured direction (either clockwise or anticlockwise). Once the data was received by the destination computer and the acknowledgement was received by the sending computer, the source computer then used to release the token so that it can again start circulating in the network. This again used to notify other computers that the network is free and the token is out on the wire to be captured by other computers if they had data that was to be transmitted. This process is technically called Token Passing.
Disadvantages of Ring Topology and their Remedies
Although establishing a network environment using ring topology was comparatively easier and it also provided a congestion and collision free network, it still had single point of failure. This means that the entire network was entirely depended on the cable on which the generated token used to travel. If because of any reason any one segment of the network failed, the entire setup used to get jeopardized. In order to overcome this disadvantage, medium or large scale organizations used the concept of Copper Distributed Data Interface or CDDI network architecture, which had two rings of the cables that were used to connect the computers with each other. The two rings were known as Primary and Secondary Rings. The secondary ring used to serve as the backup and was not functional under normal circumstances. It only used to start functioning when the primary ring failed.
Primary and secondary rings used to transmit data signals in opposite directions to each other. This means that if the primary ring was configured to transmit data in clockwise direction, the secondary ring used to transmit in an anticlockwise direction. Also, since the secondary ring was used as the backup ring for the network, only important computers (the computers that played major roles in the network, which in most cases were servers) were connected to it.
Since star topology came into existence, administrators started preferring the it over ring topology because star topology was easy to configure and was conveniently scalable.
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