Network Topology
Computers in a network
have to be connected in some logical manner. The layout pattern of the
interconnections between computers in a network is called network topology. You
can think of topology as the virtual shape or structure of the network. Network
topology is also referred to as 'network architecture.'
Devices on the network
are referred to as 'nodes.' The most common nodes are computers and peripheral
devices. Network topology is illustrated by showing these nodes and their
connections using cables. There are a number of different types of network
topologies, including bus, star, ring, mesh. Let's review these main types.
Bus
Bus topology uses one
main cable to which all nodes are directly connected. The main cable acts as a
backbone for the network. One of the computers in the network typically acts as
the computer server. The first advantage of bus topology is that it is easy to
connect a computer or peripheral device. The second advantage is that the cable
requirements are relatively small, resulting in lower cost.
One of the disadvantages
is that if the main cable breaks, the entire network goes down. This type of
network is also difficult to troubleshoot. For these reasons, this type of
topology is not used for large networks, such as those covering an entire
building.
Star
In star topology, each
computer is connected to a central hub using a point-to-point connection. The
central hub can be a computer server that manages the network, or it can be a
much simpler device that only makes the connections between computers over the
network possible.
Star topology is very
popular because the startup costs are low. It is also easy to add new nodes to
the network. The network is robust in the sense that if one connection between
a computer and the hub fails, the other connections remain intact. If the
central hub fails, however, the entire network goes down. It also requires more
cable than bus topology and is, therefore, more expensive.
Extended Star Topology
An
extended-star topology offers the same performance and reliability found in a
star topology with the addition of the ability to cover greater distances from
the central switch to the end nodes by adding repeaters or additional
connectivity devices to the segments. The extended-star topology makes more
sense in a larger physical environment and allows you to reduce degradation of
signal in places such as the far reaches of a large corporate office. Although
additional points of failure are added with each extension device, the points
of failure on any given segment of the network remain fairly easy to pinpoint.
If one segment becomes unavailable in an extended star topology, hosts
connected to other devices in the topology will still be able to communicate. By
contrast, if the central device in a star topology fails, no devices will be
able to communicate on the network.
Ring
In ring topology, the
computers in the network are connected in a circular fashion, and the data
travels in one direction. Each computer is directly connected to the next
computer, forming a single pathway for signals through the network. This type
of network is easy to install and manage.
If there's a problem in
the network, it is easy to pinpoint which connection is defective. It is also
good for handling high-volume traffic over long distances since every computer
can act as a booster of the signal. On the downside, adding computers to this
type of network is more cumbersome, and if one single computer fails, the
entire network goes down.
Mesh
In mesh topology, every
node has a direct point-to-point connection to every other node. Because all
connections are direct, the network can handle very high-volume traffic. It is
also robust because if one connection fails, the others remain intact. Security
is also high since data travels along a dedicated connection.
This type of topology
requires a lot of cables and is, therefore, expensive. Many of the connections
are also redundant since there are several different paths for data to travel
from one node to another.
