For this reason, most extended-star
topologies employ a redundant connection to a separate set of connection devices to prevent
isolation in the event of a device failure.
Ring Topologies
As the name implies, in a ring topology all the devices on a network are connected in the
form of a ring or circle. Unlike the physical bus topology, a ring type of topology has no
beginning or end that needs to be terminated. Data is transmitted in a way that is different
from the logical bus topology. In one implementation, a ???token??? travels around the ring,
stopping at each device. If a device wants to transmit data, it adds that data and the
destination address to the token. The token then continues around the ring until it ?¬?nds the
destination device, which takes the data out of the token. The advantage of using this type
of method is that no collisions of data packets occur. Two types of ring topology exist:
single-ring and dual-ring.
Single-Ring Topology
In a single-ring topology, all the devices on the network share a single cable, and the data
travels in one direction only. Each device waits its turn to send data over the network. The
single ring, however, is susceptible to a single failure, stopping the entire ring from
functioning.
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