LAN TOPOLOGIES

LAN topologies define the manner in which network devices
are organized. Four common LAN topologies exist:

1. bus,
2. ring,
3. star, and
4. tree.

These topologies are logical architectures, but the actual
devices need not be physically organized in these configurations. Logical bus
and ring topologies, for example, are commonly organized physically as a star. A
bus topology is a linear LAN architecture in which
transmissions from network stations propagate the length of the medium and are
received by all other stations.

Advantages of a Linear Bus Topology

1. Easy to connect a computer or peripheral to a linear
   bus.
2. Requires less cable length than a star topology.

Disadvantages of a Linear Bus Topology

1. Entire network shuts down if there is a break in the
   main cable.
2. Terminators are required at both ends of the backboned
   cables.
3. It is difficult to identify the problem if the entire
   network shuts down.
4. Not good as a stand-alone solution in a large
   building.

A ring topology is a LAN
architecture that consists of a series of devices connected to one another by
unidirectional transmission links to form a single closed loop. Both Token Ring
/ IEEE 802.5 and FDDI networks implement a ring topology.

A star topology is a LAN architecture in which the
endpoints on a network are connected to a common central hub, or switch, by
dedicated links. Logical bus and ring topologies are often implemented
physically in a star topology.

Advantages of a Star Topology

1. Easy to install and wire
2. No disruptions to the network when connecting or
   removing devices.
3. Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

1. Requires more cable length than a linear topology.
2. If the hub fails, nodes attached are disabled.
3. More expensive than linear bus topologies because of
   the cost of the concentrators.

A tree topology is a LAN architecture that is identical to
the bus topology, except that branches with multiple nodes are possible in this
case.

Advantages of a Tree Topology

1. Point-to-point wiring for individual segments.
2. Supported by several hardware and software vendors.

Disadvantages of a Tree Topology

Overall the type of cabling used limits length of each
segment.

1. If the backbone line breaks, the entire segment goes
   down.
2. More difficult to configure and wire than other
   topologies.