A network is a group of two or more
computer systems linked together.
A topology
is a usually schematic description of the arrangement of things in a location.
Network
topology is the layout of computer, cables and other component on a network. There
are many different types of topology and a network may be built using multiple
topologies. The different type of a network layout are as follows:
BUS TOPOLOGY
A bus
topology use a cable known as a main trunk (backbone, segment) to connect all
system together. Bus topology is very easy to set up and requires no additional
hardware such as a hub. With bus topology, when a computer send signals, it
travels around the cable length in both direction from the send computer. When
the signal reaches the end of the cable length, it bounces back and returns to
where it comes from. This is known as signal bounce signal bounce is a problem
because if another signal is sent on the same cable length, at the same time
the signal will COLLIDE and be destroyed and then must be re-transmitted.To
prevent this, there is a cable terminator to absorb the signal when it reaches
the end to prevent signal bounce.
There are
two types of bus topology: Linear Bus Topology and Distributed Bus Topology. In
Linear Bus Topology, all nodes of the network are connected to a common
transmission medium which has exactly two endpoints. Distributed Bus in which
all of the nodes of the network are connected to a common transmission medium
which has more than two endpoints that are created by adding branches to the
main section of the transmission medium.
Bus topology
uses less cable compared to mesh, ring, or the star topology. Making it less
costly and also its very Easy to install or set up such a network. The main
disadvantage of the bus topology is that it is difficult to troubleshoot, when
the network goes down, usually due to break in the network cable segment.
STAR
TOPOLOGY
With the
star topology all the computers are connected through a central device such as
a Hub or a Switch. Each workstation has a cable that goes from the network card
to the centralized device.
One
advantage of star topology is the scalability and ease of adding another system
to the network thus, connecting that system to an unused port on the
centralized device. Another benefit is that if there is break in the cable it
affects only the system that is connected to the cable, but does not affect the
entire network.
Some demerits of these topology is that,
failure from the centralized device, brings the entire network down and since a
centralized device must be present, and also every node needs its own cable to
be connected to the network, it makes establishing such networks quite costly.
MESH TOPOLOGY
The mesh
topology is not very common in computer networks today. In mesh topology every
workstation has a connection to every device present on the network. The mesh network topology employs two
schemes called full mesh and partial mesh. In the full mesh topology, each
workstation is connected directly to each of the others. In the partial mesh
topology, some workstations are connected to all the others, and some are
connected only to those other nodes with which they exchange the most data.
Fault tolerance
is the main merit of the mesh topology. If there is a break in a cable segment,
traffic can be rerouted through a different pathway because there is multiple
path way to send data from the system to another. This also makes it impossible
for the network to go down due to cable fault.
Mesh
topology is very costly due to the connection of cables to every device on the
network and the interface to create a multiple pathway between each system. Mesh
topology is very hard to administer because of numerous connections.
RING
TOPOLOGY
In the ring
topology all computers are connected via a cable that loops in a ring or
circle. Terminators are not necessary in the ring topology.
Signal
degeneration is very low because, each workstation is responsible for
regenerating or boosting the signal. With other topologies, as the signal
travels the wire, it gets weaker and weaker as a result of outside
interference, eventually it becomes unreadable if the destination system is too
far away.
In this topology,
if one computer fails or the cable link is broken, the entire network will go
down, and also cable change to the network or moving a workstation briefly or
disconnection can interrupt or bring down the entire network.
HYBRID
TOPOLOGY
Hybrid topology
is a mixture of other topologies, for example, a very popular hybrid topology
is a star-bus topology, in which a number of star topologies are connected by a
central bus, as shown in a figure.
WIRELESS TOPOLOGY
Wireless
topology is the one in which few cables are used to connect the systems. The network
is made up of transmitters that broadcast the packet using radio frequencies.
The network contains special transmitters called cells or wireless access
point. This bubble can extend to multiple rooms and possible floor in a
building. The PCs and the network has a specials transmitter receiver which
allows them to receive broadcast and transmit requested data back to the access
point. The access point is connected to a physical network by a cable which
allows it, and any wireless client, to communicate with the system on the wired
network.
PCs
connected to this type of network are mobile due to less cable use. Also
troubleshooting failed devices and cells are very easy. Failed components are
easy to find and replace.
Disadvantages
of wireless topology is a greater chance of signal interference, other devices
and machinery that emit radio frequencies or “noise” can cause interference the
signal from the access point, and also Blockage can occur in structures that
are made of thick stones or metal, which do not allow radio frequencies to pass
through them easily there affecting the signal. Another major disadvantage is
the signal interception, which means unwanted third parties can intercept
wireless without physically being on the premises.
These are the types of network topologies we have, there are other types of topologies for example tree topology,hierarchical topology etc but ,looking at their structures, you would realize that they all fall under hybrid topology.