BASICS OF COMPUTER NETWORKS, MEDIA AND TOPOLOGY

1. BY :
PRINCE KUMAR
B. SC (IT)
GAYA COLLEGE, GAYA

3.  Analogue signal: A continuous
time varying signal is called
Analogue signal.
 Digital signals: The signals having
two mode of transmission either
ON (1) or OFF (0) are Digital.
These are used as input and
output signals

4.  The process of electronically transfer of
information between two locations is known
as ‘Data Communication’.
 Some basic needs of Data Communication_
 Message : The information to be communicated.
 It may be either text, image, audio, or video file(s).
 Sender : Sender creates and transmits messages.
 Receiver : receives the information.
 Medium : The channel through which information
travel from sender to receiver.
 Protocol : Set of rules to control and co-ordinate the
communication.

6.  The medium or channel is used in data
communication may be_
 Cables : Cables or wires are used to transmit
signals from sender to receiver via a metallic
pathway. It may be of several types_
 Twisted pair : Two wires are wound around each other
in a helical form.
In general copper or Aluminium wire used in twisted pair
wire.
They are easy to handle ,flexible ,and can run more
longer distances.
Generally this is used in telephonic communications.

7.  Co-axial cables : They consist a stiff copper wire as
core surrounded by an insulating material. The
insulating material is encased by a cylindrical
conductor normally in the form of closely woven wire
mesh. Again it is covered with a plastic cover for
protection termed as jacket.
The inner copper wire is used to transmit signals and
the woven mesh is used for ground.
They have better data transmission performance w. r .t
twisted pair cables.

8.  Optical fibres : This is based on optical technology of
transmission of data as a pulse of light.
 An optical fibre cable consist of a thin strand of light
conducting glass or plastic fibre. This fibre is very thin
and flexible solid cylinder act as transmission medium
for the pulses of light.
 These fibres are claded over a core and finally
covered by a protecting plastic material called jacket.
 Faster data communication.
 Expensive in comparison of twisted pair and co-axial
cables.

10.  Microwave : Communication through microwaves can
be used when the sender and receiver are large
distance apart from each other.
These waves are used to transmit analogue signals.
this mode of transmission is greatly affected by
weather condition.
 Satellite : satellites are used to sending as well as
receiving information globally.
We can send data from one country to another country
using satellite communication.
WANs having large coverage often use satellites to link
with LANs.
Faster + less affected by weather condition.

11.  Protocols : Protocols are set of rules to
control and co-ordinate data communication.
 Some of protocols are http ,smtp ,ftp ,tcp /
ip and dns etc.
We can perform on following tasks using
protocol_
 Identification of the physical connection used.
 Error detection and correction of the improper
message .
 Initiation and Termination of the communication
session.
 Message formatting.

12.  A computer network is a systematic inter
connection of computers that enable them to
communicate with each other and share
resources, data and applications.
 Generally the computer networks are
classified on the basis of geographical area
as follows_
 Local area network (LAN)
 Wide area network (WAN)
 Metropolitan area network (MAN)
 Internet

13.  LAN :
 Network of a few computers
in a small area such as
building, homes etc.
 Used for communication
between two or more PCs.
 Medium : twisted pair wires
and co-axial wires.
 Because no. of computers is
limited so faster
communication will
happened.

14.  WAN :
 Group of computers that are
connected in a large area such as
country, continent etc.
 Generally used to connect more
LANs.
 Medium : telephone lines,
Microwaves.
 Slow rate of data transmission.

15.  MAN :
 Network of computer covers a
large city.
 Size : lies between LAN & WAN
(area of radius between 5 km to
50 km).
 Optical fibres and copper wire is
media and “router” used to
connect LANs.
 Routers is a device that direct
information packets to the
desired destination.
 Used by private organizations.

16.  The Internet :
 This is a global area network that allows computers
connected over network to share resources, data and
applications using different protocols.
 TCP/IP is used in transferring of information.
 The Internet provides us following services.
E-mail, Online chat, Online shopping, UseNet and
several applications.
Advantages: Easily availablity of information and
resources at lower cost.
Disadvantages: so many societal impacts like VIRUS,
Hacking, Malwares, and Bulk-emails.

17.  Topology means arrangements of computers
connected over a network through some
physical medium cables and determines the
shape of network and communication
pathway between nodes.
 These are some types of topology under
here_
 Hierarchical Topology
 Bus Topology
 Star Topology
 Ring Topology
 Hybrid Topology

18.  Hierarchical Topology :
 The shape of network is as like
as inverted tree.
 Each of child node has only
one parent node.
 Medium : twisted pair wire, co
axial wire and optical fibres.
 Advantages:
 Supported by most of the
hardware and software.
 Shared information is
received by each node.
 Disadvantages:
 Difficult to configure so
smaller in range.
 While root or parent node
fails the hole network is
crashed.

19.  Bus Topology :
 In this type of topology nodes are
connected to a common line called
Bus.
 If a message transmitted by any node
then its arrived to each node but that
is accessed only by which node that
one has permission otherwise it is
discarded.
 Connected by twisted pair, co axial
and optical fibres.
 Advantages:
 Less cabling.
 Having meaningful organization.
 Easy to implement.
 Disadvantages:
 If the line is crashed whole network
shall be failure.
 Difficult to regain ones line crashed.
 Degrade in speed as node increases.

20.  Star topology :
 In this arrangement several nodes
are connected to a HUB via cables
or optical fibres. When a message
is sent by a node then it first goes
to the hub and from hub
transmitted to the destination
node.
 Advantages :
 Easy error detection and
correction.
 It doesn’t matter any one of
node is crashed.
 Easy to install.
 Disadvantages :
 If hub fails hole network will
crashed.
 Large cabling.
 Expensive due to cast of hub.

21.  Ring Topology :
 Nodes are connected in the
form of ring by twisted pair as
shown in the figure.
 Message sent by any node
moves in clockwise node to
node.
 Advantage :
 Each node is connected to
every nodes.
 Addition of two node doesn’t
degrade the speed.
 Easy to install
 Disadvantage :
 Expensive relatively.
 If any node is disturbed
network will crashed.

22.  Mesh Topology :
 Each node in the network is
connected to every possible
node in the network.
 If we have n nodes in the
network there are n(n-1)/2
possible ways of connectivity.
 Advantages :
 Message delivery is more
reliable
 Minimal network congestion
due to more links.
 Disadvantages :
 Difficult to implement and
install.

23.  Hybrid Topology :
 Mixture of any two or more topologies according to the
requirement of networking arrangement.
 Generally Ring and bus topologies are arranged.
 More reliable.

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