Information Technology Reference
In-Depth Information
Bus
Ring
Star
FIGURE 2.1
The three basic LAN topologies: bus, ring, and star.
In a
bus topology
, every device is connected directly to the same medium, much
like a power bus in a computer. Classic coaxial thick Ethernet, and coaxial thin
Ethernet are examples of the bus topology. All devices on the bus can monitor data
sent by any other device, and conversely, all transmissions go roughly simultane-
ously to all other devices connected to the bus. Because the data pulses travel very
fast, and conflicts between devices can occur, a bus topology must have strict rules
to govern the operation of the network, including transmission timing, connections
to the bus, size of the bus, conflict resolution, and bus termination.
A
ring topology
connects each device to the next one on the network, in turn,
with the very last device being connected back to the first one to form the complete
ring. Data is passed from one device to the next until it reaches the destination
device. The digital signals are typically re-constituted at each device node, and a
token scheme is often employed to regulate transmissions and to keep a device from
hogging the available data bandwidth. Token-Ring and fiber distributed data inter-
face (FDDI) are examples of ring topologies.
A
star topology
connects each device to a concentration hub at the center of
the star. All communication between devices passes through the hub. Some call this
type of network a “hub and spoke,” but star is the more common name. The very
popular Ethernet hubs and switches implement the star topology in modern-day net-
