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A ring network is a chain of network devices physically or logically linked together in a ring topology. Dual-ring networks provide redundancy, but information travels slower. Ring networks are still used in fiber optic networks, despite being replaced by Ethernet for token ring technologies in the 1980s.
A ring network is a network of two or more network devices that are physically or logically linked together, one after the other, to form a device chain, with the last device in the chain docked to the first device. Ring networks are usually designed as single or double ring topologies. Multi-ring technologies involving two or more parallel rings have also been developed.
Networks are generally characterized in two ways: physically and logically. The term “physical topology” describes how devices are physically connected to each other, so a physical ring network topology has devices physically connected to each other to form a ring. The logical topology view is about how information flows. From the logical perspective, a ring network topology might have devices that are physically connected to each other such as a bus network, star network, mesh network, or tree network, but information flows from one device to another as if they were connected in a physical ring. For example, a network might be physically organized as a star network, but information might flow from one device to another as if it were a ring network.
One of the major disadvantages of a single ring network is that a disruption anywhere in the ring can cause the flow of information to fail completely. To help prevent disruptions of this nature, a second parallel counter-rotating loop or path can be added that sends information in the opposite direction. This type of redundant network is called a dual ring network. If one of the rings in a dual-ring network suffers damage, information can still reach all devices using the alternate, undamaged path.
A second disadvantage of ring networks is that information travels more slowly because data has to pass through each device as it makes its way through the network. Despite this limitation, ring topologies are still employed in fiber optic networks such as fiber distributed data interface networks (FDDI), synchronous optical network networks (SONNET), and synchronous digital hierarchy networks (SDH). When these high-speed networks incorporate a dual-ring physical topology, they further benefit from the redundancy provided by this type of topology.
Ring networks became popular in the 1980s when logical ring network topologies were used in token ring technologies. The inherent limitations of a ring network, coupled with compatibility issues between token ring and other protocols, have led to the replacement of token ring technologies with newer data transport methods such as Ethernet. Although Ethernet has continued to increasingly supplant the protocols used with fiber-optic ring networks, the use and development of the ring network for carrying high-speed data has continued.
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