The Advantages of Token Ring Networks

Collision Domains

Devices connected on a network use electric impulses sent through cabling in order to transmit information. These electric pulses go to every device connected to the same network segment, forming a collision domain. The intended recipient receives and interprets the data. All other devices ignore it. If two devices within the same collision domain transmit data at the same time, a collision occurs. When this happens, the data is lost and must be resent. On a large or busy network, the amount of data that must be retransmitted due to collisions could significantly hamper network performance.

The token ring network is built around the idea of a logical ring, or loop, of network nodes. Physically, the network utilizes a star topography, where each network node is connected to a central device, called the media access unit. Logically, the devices act in a ring, utilizing a pulse of data called the token frame. When no other data is being transmitted, a designated device will generate the token and pass it to the next node in the ring. If the next device has no data to transmit, it passes the token on to the next node. When a device is ready to transmit, it must wait till it receives the token. Instead of passing the token along, it enters the data into the loop. The data passes along the loop until it reaches the destination. Once the data is received, the token is regenerated and the process continues.

The token forces each device in the token ring network to wait until it has the token before initiating any form of communication. This ensures that the only device sending a communication through the network is the one that currently has the token. This virtually eliminates any form of data collisions. Data can be sent without having to worry about retransmitting. Token ring networks don't lose any bandwidth due to retransmitted data and data integrity could be higher in most cases.

For a time, Token Ring networks were preferred in situations where data integrity was critical and data collisions could have an adverse effect on the outcome of operations, such as networks used for research processing. As Ethernet networks became faster, development and implementation of Token Ring networks dropped drastically. Today, Token Ring networks have no advantage over other networking topographies, such as Ethernet. They also are more expensive, harder to set up and require equipment difficult to locate.