Data communication and computer networking

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CHAPTER-4
DATA COMMUNICATION AND
COMPUTER NETWORKING
By Kenbon.A

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CONTENTS
Definition
Modes of Data Communication
Transmission Media
Computer Networking
Types of Networks

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Data Communication
Communication is the process of sharing a
message.
Data communications refers to the sharing
of a virtual message.
Electronic communications, like emails
and instant messages, as well as phone
calls are examples of data communications.

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For data communication to be effective, the
following three fundamental characteristics
should be considered.
a. Delivery: The system must deliver data to
the correct of the intended destination.
b. Accuracy: The system must deliver data
accurately (error free)
c. Timeliness: The system must deliver data
in a timely manner without enough time
lags.

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Elements of Data
Communication
There are five basic components in data
communication system:
A. Message: It is the information that is to be
communicated.
B. Sender: The sender is the device that sends the
message
C. Receiver: The receiver is device that receives the
message
D. Medium: The transmission medium is the physical
path that communicates the message from sender
to receiver.

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E. Protocol: Protocol refers to a set of
rules that coordinates or governs the
exchange of information.
• Both the sender and receiver should follow
the same protocol to communicate data.
• Without the protocol, the sender and
receiver cannot communicate with each
other.

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Modes of Data Communication
The manner in which data is transmitted
from one location to another location is
called data transmission mode.
There are three ways or modes for
transmitting data from one location to
another. These are:-
I. Simplex
II. Half duplex
III.Full duplex

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I. Simplex Mode: - In this transmission signals
(information) are transmitted in only one
direction: One station is sender and the other
is receiver.
• Television Transmission can be considered as an
example of simplex mode of transmission
where the satellite only transmits the data to the
television, vice versa is not possible.

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II. Half Duplex: - In half duplex mode, data can
be transmitted in both directions but only in
one direction at a time.
• During any transmission, one is the transmitter
and the other is receiver.
• The most common example of half-duplex
transmission is the wireless handsets (generally
used by military personnel) where one user talks
at a time and another listens.

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III.Full Duplex: - In this transmission signals
transmitted in both direction, both stations
may transmit simultaneously. The medium
carries signals in both directions at the same
time. It can be compared to a two way road
with traffic flowing in both directions.
A common example of full duplex transmitting
mode is the Telephone network, where two
people communicate over a telephone line; both
can talk as well as listen at the same time.

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Data transmission
Data transmission refers to the movement of data in
form of bits between two or more digital devices.
When we enter data into the computer via keyboard,
each keyed element is encoded by the electronics
within the keyboard into an equivalent binary coded
pattern, using one of the standard coding schemes that
are used for the interchange of information.

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Transmission Media
The transmission media are media through which
data is transferred.
Transmission media can be defined as physical
path between transmitter and receiver in a data
transmission system.

Classes of transmission media
1. Guided Media
Guided transmission Media use a cabling system that
guide the data signals along a specific path.
Cabling refers to transmission medium that consists
of cable of various metals like Copper, Tin or Silver.
Some of the guided transmission media are twisted
pair cable, coaxial cable, and optical fiber cables.
I. Twisted pair Cable: Pairs of wires are twisted
together which are surrounded by an insulating
material and an outer layer called jacket and they
are available in two forms: Unshielded and
Shielded.
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Shielded Twisted Pair (STP) Cable
Twisted pair network cables are often shielded in an
attempt to prevent electromagnetic interference.
This type of shielding protects cable from external
electromagnetic interference (EMI) entering or exiting the
cable and also protects neighboring pairs from crosstalk.

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Advantages of Shielded Twisted Pair Cable
✓ Easy to install
✓ Performance is adequate
✓ Can be used for Analog or Digital transmission
✓ Higher capacity than unshielded twisted pair
✓ Eliminates crosstalk
Disadvantages of Shielded Twisted Pair Cable
✓ Difficult to manufacture
✓ Heavy

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Unshielded Twisted Pair (STP) Cable
It is the most common type of telecommunication
when compared with Shielded Twisted Pair Cable
which consists of two conductors usually copper, each
with its own color plastic insulator
UTP cables consist of 2 or 4 pairs of twisted cable.
Most UTP cable uses RJ45 connectors, which look like
telephone connectors (RJ11) but have eight wires
instead of four.

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Advantages of Unshielded Twisted Pair Cable
Installation is easy
✓ Flexible
✓ Cheap
✓ It has high speed capacity
Disadvantages of Unshielded Twisted Pair
Cable
✓ Bandwidth is low when compared with Coaxial Cable
✓ Provides less protection from interference

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Coaxial Cable
 Coaxial cable is a type of cable that has an inner conductor surrounded by
a tubular insulating layer, surrounded by a tubular conducting shield.
The inner conductor and the outer shield share a geometric axis.
Many coaxial cables have an insulating outer sheath or jacket.
Its applications include feedlines connecting radio transmitters and
receivers with their antennas, computer network connections, digital
audio, and distributing cable television signals.

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Advantages of Coaxial Cable
✓ Bandwidth is high
✓ Used in long distance telephone lines.
✓ Transmits digital signals at a very high rate of
10Mbps.
✓ Much higher noise immunity
Disadvantages of Coaxial Cable
✓ Single cable failure can fail the entire network.
✓ Difficult to install and expensive when compared with
twisted pair.

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Optical Fiber Cable
Optical fiber cabling is an excellent transmission medium
for its high data capacity and supported long distances.
It has a fiber/glass core within a rubber outer coating
and uses beams of light rather than electrical signals to
relay data.
Because light doesn't diminish over distance.

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Advantages of Fibre Optic Cable
✓ Higher bandwidth
✓ Less signal attenuation
✓ Immunity to electromagnetic interference
✓ Resistance to corrosive materials
✓ Light weight
✓ Greater immunity to tapping
 Disadvantages of Fibre Optic
✓ Installation and maintenance
✓ Unidirectional light propagation
✓ High Cost

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2. Unguided Media
Unguided media transport electromagnetic
waves without using a physical conductor.
This type of communication is often
referred to as wireless communication.
Unguided media include radio,
microwaves, infrared and lasers through
the air.

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COMPUTER NETWORKING
Computer networking is defined as the interconnection of
computers and other communication equipment’s connected
by a communication channel.
The communication channel (medium) will be either
wired communication channel or wireless communication
channel.
Wired communication channel includes the different cable
types like twisted pair cable, co-axial cable or fiber optic
cable and Wireless communication channel includes
microwave or satellite communication system.

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Importance of Computer Networking
The two major benefits of computer networking include:
Computer networks are used for resource sharing
and
Computer networks are used as a communication
medium
 Resource sharing
• A computer network is a collection of computers and
other devices that communicate to share data, hardware,
and software.
• the importance of computer networking as a resource
sharing includes:

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Data /Information Sharing: - This involves
access to remote or distributed database and
files containing data, text, image or video.
Program/software Sharing: - Programs stored
on a central server can simultaneously be
accessed and loaded for execution on several
local computers.
Device / hardware Sharing:- Computer
networks enable us to share expensive hard
wares (or peripheral devices). This includes
access to computing resources such as other
computers, printers, scanners etc.

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 Communication medium
•Uses of computers as a
communication medium includes:
Electronic mail (e-mail)
Video conferencing

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Types of Networks
Networks are commonly classified by ownership
as:
1. Private Networks
2. Public Networks
• Private Network: Private network is the type of
network which is built by an organization for its
exclusive use. Example the network in BHU
campus is a private network.
• Public Network: is established and operated by
a network service provider (NSP)for the
specific purpose of providing services to
customer organizations and individuals.

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Example:
ETC (Ethiopian Telecommunications
Corporation)
Safaricom
According to their geographical range
networks are classified in to three i.e.
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)

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A. Local Area Network (LAN)
LAN is the interconnection of computers and other
peripheral devices with in a limited geographical area.
For example, the network of computers with in the
University campus, a school, a factory or an office.
The connection is usually made through a cable.
B. Metropolitan Area Network (MAN)
 MAN is the interconnection of LANs within a city
wide geographical area.

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C. Wide Area Network (WAN)
• WAN can cover large geographical area
by using one or more communication
channels such as:
Telephone lines
Fiber optic cables
Microwave and satellite communication systems
• WANs span large areas such as countries or the
entire world

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Network Topologies
A Network topology is the layout or arrangement of
computers in a network. The most common
network topologies are:
Bus topology
Ring topology
Star topology
Mesh topology
Tree topology

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Bus Topology
Bus topology is a network type in which every computer
and network device is connected to single cable.
It transmits the data from one end to another in single
direction.
No bi-directional feature is in bus topology.

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Advantages of the Bus Network
Easy to install and maintain.
It is cheaper because it requires less wiring.
It is comfortable for a small and temporary network.
Easy to add a computer to the network.
Internet and electricity cables can go together.
Disadvantages of the Bus Network
It is known as passive topology because computers do not
regenerate the signal.
Lose signal over distance (you can use repeaters).
Its main drawback is that if the cable breaks at some point,
the network is entirely inoperative.
The speed in this network connection is deficient.
Equipment limit depending on the signal quality.
Performance decreases as the network grows.

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Star Topology
In star topology, all the devices are
connected to a single hub through a cable.
This hub is the central node and all others
nodes are connected to the central node.
The hub can be passive in nature i.e. not
intelligent hub such as broadcasting devices,
at the same time the hub can be intelligent
known as active hubs.
Active hubs have repeaters in them.

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Advantages of Star Topology
It is very reliable – if one cable or device fails then all the others
will still work
It is high-performing as no data collisions can occur
Less expensive because each device only need one I/O port and
wishes to be connected with hub with one link.
Easier to put in
Robust in nature
Easy fault detection because the link are often easily identified.
No disruptions to the network when connecting or removing
devices.
Each device requires just one port i.e. to attach to the hub.
If N devices are connected to every other in star, then the
amount of cables required to attach them is N. So, it’s easy to
line up.

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Disadvantages of Star Topology
Requires more cable than a linear bus .
If the connecting network device (network switch) fails,
nodes attached are disabled and can’t participate in
network communication.
More expensive than linear bus topology due to the value
of the connecting devices (network switches)
If hub goes down everything goes down, none of the
devices can work without hub.
Hub requires more resources and regular maintenance
because it’s the central system of star .
Extra hardware is required (hubs or switches) which adds
to cost
Performance is predicated on the one concentrator i.e. hub.

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Ring Topology
In this topology, it forms a ring connecting a device with
its exactly two neighboring devices.
The following operations takes place in ring topology are:
 One station is known as monitor station which takes all
the responsibility to perform the operations.
 To transmit the data, station has to hold the token. After
the transmission is done, the token is to be released for
other stations to use.
 When no station is transmitting the data, then the token
will circulate in the ring.

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Advantages of ring topology
It provides alternative round
Cheap to install and extend
Easy to reconfigure
Each computer has equal access to resources
Additional components do not affect the performance of a network
There is no need for a network server to control the connectivity between
workstations
Performance is better than that of bus topology
It is less costly than a star topology
Data transmission is high speed
Traffic is unidirectional
In comparison with bus, ring, a tree is better than handling load
Adding or removing of a network node is easy, as the process requires
changing only two connections
Good communication over long distance
Handle high volume traffic
Fault identification is easy
No data collision

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Disadvantages of ring topology
A ring is not very scalable
Troubleshooting is difficult
Adding or deleting the computer disturb the network activity
Failure of one computer the whole network
Unique wiring require
More complex networking and operational protocol
A network is highly dependent on the wire which connects different
component
This topology is ordered for all computer to communicate with each
other, all computers must be turned on
Total dependence upon the one cable
Data packets must pass through every computer between the sender and
also a recipient side, therefore, this makes it slower
If any of the nodes is fail then the ring is broken or fail and data cannot
be transmitted successfully

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Tree Topology
Tree topology is the combination of the bus and the star topology.
Tree topology allows users to have many servers on the network.
Tree topology follows a hierarchical pattern whereby each level is
connected to the next higher level in a symmetrical pattern.
It connects multiple star topologies to another star topology
network.
Tree topology is the best when the network is large and not for a
small network because it is a waste of cables to use it.

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Advantages of Tree Topology :
This topology is the combination of bus and star topology.
This topology provides a hierarchical as well as central data
arrangement of the nodes.
As the leaf nodes can add one or more nodes in the hierarchical
chain, this topology provides high scalability.
The other nodes in a network are not affected if one of their
nodes gets damaged or does not work.
Tree topology provides easy maintenance and easy fault
identification can be done.
A callable topology. Leaf nodes can hold more nodes.
Supported by several hardware and software vendors.
Point-to-point wiring for individual segments.
Tree Topology is highly secure.
It is used in WAN.
Tree Topology is reliable.

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Disadvantages of Tree Topology
This network is very difficult to configure as compared to the
other network topologies.
The length of a segment is limited & the limit of the segment
depends on the type of cabling used.
Due to the presence of a large number of nodes, the network
performance of tree topology becomes a bit slow.
Requires a large number of cables compared to star and ring
topology.
As the data needs to travel from the central cable this creates
dense network traffic.
The Backbone appears as the failure point of the entire segment
of the network.
Treatment of the topology is pretty complex.
The establishment cost increases as well.
If the bulk of nodes is added to this network, then the
maintenance will become complicated.

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Mesh Topology
In mesh topology, every device is connected to another
device via particular channel.
Every device is connected with another via dedicated
channels.
These channels are known as links:
 If suppose, N number of devices are connected with
each other in mesh topology, then total number of ports
that is required by each device is N-1.
 If suppose, N number of devices are connected with each
other in mesh topology, then total number of dedicated
links required to connect them is N(N-1)/2.

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Advantages of Mesh Topology
Failure during a single device won’t break the network.
There is no traffic problem as there is a dedicated point
to point links for every computer.
Fault identification is straightforward.
This topology provides multiple paths to succeed in the
destination and tons of redundancy.
It provides high privacy and security.
Data transmission is more consistent because failure
doesn’t disrupt its processes.
Adding new devices won’t disrupt data transmissions.
This topology has robust features to beat any situation.
A mesh doesn’t have a centralized authority.

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Disadvantages of Mesh Topology
It’s costly as compared to the other network topologies.
Installation is extremely difficult in the mesh.
Power requirement is higher as all the nodes will need
to remain active all the time and share the load.
Complex process.
The cost to implement mesh is above other selections.
There is a high risk of redundant connections.
Each node requires a further utility cost to think about.
Maintenance needs are challenging with a mesh.

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Hybrid Topology
• A network structure whose design contains more
than one topology is said to be hybrid topology.
• Hybrid topology inherits merits and demerits of all
the incorporating topologies.

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What is HTTP?
HTTP stands for HyperText Transfer Protocol and
is the foundation of the World Wide Web.
HTTP is used when browsers want to get
connected to websites.
They communicate by sending HTTP requests and
receiving HTTP responses.

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World Wide Web (WWW)
WWW can be defined as the collection of different
websites around the world, containing different
information shared via local servers(or
computers).
The World Wide Web is based on several different
technologies: Web browsers, Hypertext Markup
Language (HTML) and Hypertext Transfer
Protocol (HTTP).

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URL
Also known as an internet address or web
address, a URL (Uniform Resource
Locator) is a URI and standardized naming
convention for addressing documents accessible
over the Internet and Intranet.
The URL makes it possible for a computer to
locate and open a web page on a different
computer on the Internet.
An example of a URL is
https://www.computerhope.com.

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Internet
The Internet is a network built by the cooperative
connectivity of millions of computers that are linked
together. The Internet is made up of:
People: The network is used and developed by
people.
Resources: A group of resources that can be
accessed through those networks.
A setup for collaboration: It is a collaborative
arrangement that comprises members of the
research and education committees from all around
the world.

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Intranet
An intranet is a private network that only
employees of a company may access.
It's the most restrictive of the three networks.
Intranets differ from the Internet in that private
servers are not accessible to the general public.

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Extranet
An extranet is a type of network that allows
external users to access an organization's intranet.
An extranet is similar to an intranet, except that it
is accessed through a Web portal.
An intranet is a private network that is only
available to members of the same group,
corporation, or organization.
Extranets are quickly becoming a popular way for
business partners to securely communicate
information.

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