Computer Network
Topologies
The term topology
refers to the way a network is laid out, either physically or logically. The
connection of two or more devices forms a link and two or more links forms a
topology. The topology of a network is the geometric representation of the relationship of all the
links and linking devices to one another. Basically, there are five topologies
– mesh, star, tree, bus, and ring.
- 1) Mesh:-
Every devices has a dedicated point-to-point link to each other devices in a
mesh topology. Therefore a fully connected mesh network has n(n-1)/2 physical
channels to link n devices.
Mesh
topology has several advantages:-
a)
The use of
dedicated links guarantees that each connection can carry its own data
load, therefore minimizing the traffic
problems which can take place if links much be shared by multiple devices.
b)
It is
robust. It does not incapacitate the entire system when one link damages.
c)
It
enforces privacy or security. Physical boundaries prevent other users from
gaining access to messages.
d)
The
point-to-point links make fault identification and fault isolation easy. traffic
can be routed to avoid links with suspected problems.
- 2)
Star:- In
a star topology every device has a dedicated point-to-point link only to a
central controller called the hub. The devices cannot be directly linked to
each other, but the controller acts as exchange. When one device want to send
data to another, it sends the data first to be hub which then relays it to the
other devices connected to it.
The
advantages of star topology are-
a)
It is less
expensive as compared to mesh.
b)
Every
devices required only one link and one I/O port to connect it to any number of others.
This makes it easy it install and
reconfigure.
c)
Less
cabling is required.
d)
Every to
add, delete, or move devices as it involves only one connection between a
device and hub.
e)
Robustness;
it implies that if one link fails, only that link is affected other remain
active.
- 3)
Tree:- A
variation of a star topology is a tree topology. Notes in tree are linked to
the central hub as is done in star but every devices is not directly plugged
into central hub. The majority of the devices connect to a secondary hub that
in turn is connected to the central hub.
The
advantages of Tree topology are-
a)
It permits
the network to isolate and prioritizes communications from various computers.
b)
It permits
more devices to be attached to a single central hub and can increase the
distance a signal can travel between devices.
- 4)
Bus :- A
bus topology describes a multipoint configuration. One long cable acts as a
backbone to link all the devices in the network.
Advantage
of bus topology is ease of installation. Backbone cable can be laid along the
most efficient path, then connected to the nodes by drop lines of various
lengths. Also , bus uses less cabling than mesh, star or tree topologies.
- 5)
Ring:-
every device has a dedicated point to point line configuration only with the
two devices on the either side of it in ring topology. A signal is passed along
the ring in one direction, from device to device, until it reaches its
destination. Each device has a repeater which regenerates the bits and passes
them along to another device.
The advantages
of ring topology-
a)
It is easy
to install and reconfigure.
b)
It is easy
to add or delete a device as it requires to move only two connection.
c)
Fault
isolation is simplified.
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