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Outcome of this chapter
 Basics of data communication and the components
needed for it
 The client server model
 Different network topologies
 Different network types
 Physical mediums that connect computers
 Different transmission lines
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Computer Network
 A computer network consists of a collection of
computers, printers and other equipment that is
connected together so that they can communicate
with each other.
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Figure : A simple computer network

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Data Communication
 Data communications are the
exchange of data between
two devices via some form of
transmission medium such as
a wire cable.
 For data communications to
occur, the communicating
devices must be part of a
communication system made
up of a combination of
hardware (physical
equipment) and software
(programs).
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Components of Data Communication
1. Message
2. Sender
3. Receiver
4. Medium or Communication Channel
5. Encoder and Decoder
6. Protocol
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Message
 The message is the information or data that is to be
communicated.
 It may consist of text, numbers, pictures, sounds, videos or
any combination of these.
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Components of Data Communication

 Sender
• A device that is used for sending messages (or data) is
called sender.
• It is also called transmitter or source.
• The sender can be a computer, telephone, or a video camera etc.
• Usually, a computer is used as sender in data communication
system.
 Receiver
• A device that is used for receiving messages is called receiver.
• It is also known as sink.
• The receiver can be a computer, telephone set, printer, or a fax
machine etc.
• Usually, a computer is also used as receiver in data
communication system.
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Components of Data Communication

 Medium
 The path through which data is
transmitted (or sent) from one
location to another is called
transmission medium.
 It is also called communication
channel.
 It may be a wire, or fiber optic
cable, or telephone line etc.
 If the sender and receiver are
within a building, a wire is used as
the medium.
 If they are located at different
locations, the medium may be
telephone line, fiber optics, and
microwave or satellite system.
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Components of Data Communication

Protocol:
 A protocol is a set of rules that govern data
communications.
 It represents an agreement between the communicating
devices.
 Without a protocol, two devices may be connected but not
communicating, just as a person speaking French cannot
be understood by a person who speaks only Japanese.
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Components of Data Communication

 Encoder and Decoder: In communication systems,
computers are used for senders and receivers. A computer
works with digital signals. The communication channels
usually use analog signals. The encoder and decoder are
used in communication systems to convert signals from
one from to another.
 Encoder: The encoder is an electronic device. It receives
data from sender in the form of digital signals. It converts
digital signals into a form that can be transmitted through
transmission medium.
 Decoder: The decoder is an electronic device. It receives
data from transmission medium. It converts encoded
signals (i.e. analog signals) into digital form.
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Components of Data Communication

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Understanding Client server interaction
There are two main types of computers on a network: server and client.
Server Computer: A server is a network computer that contains
resources that are shared with other computers within the network.
A computer that is being served with these resources is a client.
What Servers Do:
 Data server stores and serves database information to client
computers.
 Application server holds a web-based application and its
data. It processes requests from users of the application and
sends results to the client computers.
 Web server stores and serves web pages over the Internet.
 File server stores and shares data files and programs among
users on a network.
 Email server stores and moves mail across local networks
and over the Internet.
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Computer Network Types
 Personal Area Network (PAN):
 A Personal Area Network or
simply PAN, is smallest network
which is very personal to a user.
 This may include Bluetooth
enabled devices or infra-red
enabled devices.
 PAN has connectivity range up to
10 meters.
 PAN may include wireless
computer keyboard and mouse,
Bluetooth enabled headphones,
wireless printers and TV remotes
for example.
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 Local Area Network (LAN):
 A computer network spanned
inside a building and operated
under single administrative
system is generally termed as
Local Area Network.
 Usually, Local Area Network
covers an organization’s
offices, schools,
college/universities etc.
 Resources like Printers, File
Servers, Scanners and internet
is easy sharable among
computers.
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Computer Network Types

 Metropolitan Area Network
(MAN):
 A metropolitan area
network (MAN) is computer
network larger than a local area
network, covering an area of a
few city blocks to the area of an
entire city, possibly also
including the surrounding
areas.
 A MAN might be owned and
operated by a single
organization, but it usually will
be used by many individuals
and organizations.
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Computer Network Types

 Wide Area Network (WAN):
 A wide area network (WAN) is
a geographically dispersed
telecommunications network.
 The term distinguishes a
broader telecommunication
structure from a local area
network (LAN).
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Computer Network Types

Network Topologies
 A Network Topology is the way computer systems or
network equipment connected to each other.
 Point-to-point: Point-to-point networks contains
exactly two hosts (computer or switches or routers or
servers) connected back to back using a single piece of
cable.
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 Bus Topology :
 All devices are connected to this shared line.
 It is one of the simple forms of networking where a
failure of a device does not affect the others. But failure
of the shared communication line make all other devices
fail.
 Both ends of the shared channel have line terminator.
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Network Topologies

 Star topology:
 All hosts in star topology are connected to a central
device, known as Hub device, using a point-to-point
connection.
 Star topology is not expensive as to connect one more
host, only one cable is required and configuration is
simple.
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Network Topologies

 Ring topology:
 In ring topology, each host machine connects to exactly two
other machines, creating a circular network structure.
 When one host tries to communicate or send message to a
host which is not adjacent to it, the data travels through all
intermediate hosts.
 Failure of any host results in failure of the whole ring.
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Network Topologies

 Mesh topology:
 In this type of topology, a host is
connected to one or two or more than
two hosts.
 Full Mesh: All hosts have a point-to-
point connection to every other host in
the network. Thus for every new host
n(n-1)/2 cables (connection) are
required. It provides the most reliable
network structure among all network
topologies.
 Partially Mesh: Not all hosts have
point-to-point connection to every
other host. Hosts connect to each other
in some arbitrarily fashion. This
topology exists where we need to
provide reliability to some host whereas
others are not as such necessary. 23
Network Topologies

Internet, Intranet, Extranet
 The Internet: A means of connecting a
computer to any other computer anywhere in
the world via dedicated routers and servers.
When two computers are connected over the
Internet, they can send and receive all kinds
of information.
 Intranet: An intranet is a computer
network that uses Internet Protocol technology
to share information, operational systems, or
computing services within an organization.
 Extranet: An extranet is a private network
that uses Internet technology and the
public telecommunication system to
securely share part of a business's
information or operations with suppliers,
vendors, partners, customers, or other
businesses.
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Network media and connector
 Transmission Medium : A
transmission medium can be
broadly defined as anything that
can carry information from a source
to a destination.
 Magnetic Media:
 One of the most convenient ways to
transfer data from one computer to
another, even before the birth of
networking, was to save it on some
storage media and transfer physical
from one station to another.
 Though it may seem odd in today’s
world of high speed Internet, but
when the size of data to transfer is
huge, Magnetic media comes into
play.
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 Twisted Pair Cable: A twisted pair cable is
made of two plastic insulated copper wires
twisted together to form a single media. Out
of these two wires only one carries actual
signal and another is used for ground
reference. The twists between wires are
helpful in reducing noise (electro-magnetic
interference) and crosstalk. There are two
types of twisted pair cables available:
 Shielded Twisted Pair (STP) Cable
 Unshielded Twisted Pair (UTP) Cable
 STP cables comes with twisted wire pair covered
in metal foil. This makes it more indifferent to
noise and crosstalk.
 UTP has seven categories, each suitable for
specific use. In computer networks, Cat-5, Cat-5e
and Cat-6 cables are mostly used. UTP cables are
connected by RJ45 connectors.
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Network media and connector

Coaxial Cable:
 Coaxial cables have two wires of copper.
The core wire lies in center and is made of
solid conductor.
 Core is enclosed in an insulating sheath.
Over the sheath the second wire is
wrapped around and that too in turn
encased by insulator sheath. This all is
covered by plastic cover.
 Because of its structure coax cables are
capable of carrying high frequency signals
than that of twisted pair cables.
 The wrapped structure provides it a good
shield against noise and cross talk.
 Coaxial cables provide high bandwidth
rates of up to 450 mbps.
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Network media and connector

Fiber Optics:
 Fiber Optic works on the properties of light.
 When light ray hits at critical angle it tends to
refracts at 90 degree. This property has been
used in fiber optic.
 The core of fiber optic cable is made of high
quality glass or plastic.
 From one end of it light is emitted, it travels
through it and at the other end light detector
detects light stream and converts it to electric
data form.
 Fiber Optic provides the highest mode of
speed.
 It comes in two modes; one is single mode fiber
and second is multimode fiber.
 Single mode fiber can carries single ray of light
whereas multimode is capable of carrying
multiple beams of light.
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Network media and connector

 Wireless:
 Wireless communication is the transfer of information
between two or more points that are not connected by
an electrical conductor.
 Wireless operations permit services, such as long-range
communications, that are impossible or impractical to
implement with the use of wires. The term is commonly
used in the telecommunications industry to refer to
telecommunications systems (e.g. radio transmitters
and receivers, remote controls etc.)
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Network media and connector

Wireless Technology
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Transmission Modes
 Simplex:
 A simplex connection is a connection in which the data
flows in only one direction, from the transmitter to the
receiver.
 This type of connection is useful if the data do not need to
flow in both directions (for example, from your computer to
the printer or from the mouse to your computer).
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 Half-Duplex :
 A half-duplex connection (sometimes called
an alternating connection or semi-duplex) is a
connection in which the data flows in one direction or
the other, but not both at the same time.
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Transmission Modes

 Full-Duplex :
 A full-duplex connection is a connection in which the
data flow in both directions simultaneously.
 Each end of the line can thus transmit and receive at the
same time.
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Transmission Modes

Thank You
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