Introduction to Computer Networking

NETWORKING CONCEPTS
BY : ROOPA .S
COMPUTER SCIENCE LECTURER

WHAT IS A NETWORK?
 A network is a group of two or more computers that are linked together.
 Networks are usually used to share resources, exchange files or communicate
with other users.
 A network is a set of nodes connected by communication links.
 A node can be a computer, printer, or any other device capable of sending or
receiving data from the other node through the network.

GOALS OF NETWORKING
 Resource Sharing –
Many organization has a substantial number of computers in operations, which are located apart. Ex. A
group of office workers can share a common printer, fax, modem, scanner etc.
 High Reliability –
If there are alternate sources of supply, all files could be replicated on two or, machines. If one of them is
not available, due to hardware failure, the other copies could be used.
 Communication –
Network users, located geographically apart, may converse in an interactive session through the
network. In order to permit this, the network must provide almost error-free communications.
 Flexible access –
Files can be accessed from any computer in the network. The project can be begun on one computer
and finished on another.
Other goals include Distribution of processing functions, Centralized management, and allocation of
network resources, Compatibility of dissimilar equipment and software, Good network performance,
Scalability, Saving money, Access to remote information, Person to person communication etc.,

NEED OF NETWORKING
Computer networks help users on the network to share the resources and in
communication. Can you imagine a world now without emails, online newspapers,
blogs, chat and the other services offered by the internet?
The following are the important uses and benefits of a computer network.
File sharing: Networking of computers helps the network users to share data
Hardware sharing: Users can share devices such as printers, scanners, CD-ROM
drives, hard drives etc. Without computer networks, device sharing is not possible.
Application sharing: Applications can be shared over the network, and this allows
to implement client/server applications
User communication: Networks allow users to communicate using e-mail,
newsgroups, and video conferencing etc.
Network gaming: A lot of network games are available, which allow multi-users to
play from different locations.
Voice over IP (VoIP): Voice over Internet Protocol (IP) is a revolutionary change in
telecommunication which allows to send telephone calls (voice data) using standard
Internet Protocol (IP) rather than by traditional PSTN

ARPANET(ADVANCED RESEARCH PROJECTS AGENCY NETWORK )
Advanced Research Projects Agency Network (ARPANET) was an early packet-switching
network and the first network to implement the TCP/IP protocol suite. Both technologies
became the technical foundation of the Internet.
What was Arpanet used for?
ARPANET was the network that became the basis for the Internet. Based on a concept first
published in 1967, ARPANET was developed under the direction of the U.S. Advanced
Research Projects Agency (ARPA). In 1969, the idea became a modest reality with the
interconnection of four university computers.

OSI REFERENCE MODEL ( OPEN SYSTEM INTERCONNECTION)
•OSI stands for Open System Interconnection is a reference model that describes how
information from a software application in one computer moves through a physical medium to
the software application in another computer.
•OSI consists of seven layers, and each layer performs a particular network function.
•OSI model was developed by the International Organization for Standardization (ISO) in 1984,
and it is
now considered as an architectural model for the inter-computer communications.
•OSI model divides the whole task into seven smaller and manageable tasks. Each layer is
assigned a particular task.
•Each layer is self-contained, so that task assigned to each layer can be performed independently.

WHAT IS A PROTOCOL IN NETWORKING?
A protocol is a set of rules and guidelines for communicating data.
Rules are defined for each step and process during communication
between two or more computers.
Networks have to follow these rules to successfully transmit data.

TCP/IP MODEL (TRANSMISSION CONTROL PROTOCOL / INTERNET
PROTOCOL)
•The TCP/IP model was developed prior to the OSI model.
•The TCP/IP model is not exactly similar to the OSI model.
The TCP/IP model is a condensed version of the OSI reference model
consisting of the following 4 layers:
1. Application Layer.
2. Transport Layer.
3. Internet Layer.
4. Network Access Layer.

The four layers of the TCP/IP model
TCP/IP is a data link protocol that is used on the internet. Its model is split into four distinct layers. Used together,
they can also be referred to as a suite of protocols.
Data link layer/Network Interface
The data link layer (also called the link layer, network interface layer, or physical layer) is what handles the physical
parts of sending and receiving data using the Ethernet cable, wireless network, network interface card, device
driver in the computer, and so on.
Internet layer
The internet layer (also called the network layer) controls the movement of packets around the network.
Transport layer
The transport layer is what provides a reliable data connection between two devices. It divides the data in
packets, acknowledges the packets that it has received from the other device, and makes sure that the other
device acknowledges the packets it receives.
Application layer
The application layer is the group of applications that require network communication. This is what the user
typically interacts with, such as email and messaging. Because the lower layers handle the details of
communication, the applications don’t need to concern themselves with this.

DIFFERENCE BETWEEN TCP/IP MODEL AND OSI MODEL
TCP/IP OSI
TCP refers to Transmission Control Protocol. OSI refers to Open Systems Interconnection.
TCP/IP has 4 layers. OSI has 7 layers.
TCP/IP is more reliable OSI is less reliable
TCP/IP does not have very strict boundaries. OSI has strict boundaries
TCP/IP follow a horizontal approach. OSI follows a vertical approach.
TCP/IP uses both session and presentation layer in the application layer itself. OSI uses different session and presentation layers.
TCP/IP developed protocols then model. OSI developed model then protocol.

HTTP (HYPER TEXT TRANSFER PROTOCOL)
HTTP stands for Hyper Text Transfer Protocol
WWW(World Wide Web) is about communication
between web clients and servers
Communication between client computers and web
servers is done by sending HTTP Requests and
receiving HTTP Responses

WORLD WIDE WEB COMMUNICATION
The World Wide Web is about communication between web clients and web servers.
Clients are often browsers (Chrome, Edge, Safari), but they can be any type of program or
device.
Servers are most often computers in the cloud.
HTTP Request / Response : Communication between clients and servers is done
by requests and responses:
1.A client (a browser) sends an HTTP request to the web
2.An web server receives the request
3.The server runs an application to process the request
4.The server returns an HTTP response (output) to the browser
5.The client (the browser) receives the response

The HTTP Request Circle
A typical HTTP request / response circle:
1.The browser requests an HTML page. The server returns an HTML file.
2.The browser requests a style sheet. The server returns a CSS file.
3.The browser requests an JPG image. The server returns a JPG file.
4.The browser requests JavaScript code. The server returns a JS file

FILE TRANSFER PROTOCOL (FTP)
What does FTP mean?
The File Transfer Protocol (FTP) is a standard network protocol used for
the transfer of computer files between a client and server on a computer
network.
Advantages of FTP
1. Used to transfer files from one network to another.
2. It is an effective way to get geographically dispersed group to co-operate
on a project.
3. It is a popular way to share information over the internet. FTP works as
client/server process.

SLIP/PPP (SERIAL LINE /POINT TO POINT PROTOCOL)
The Serial Line Internet Protocol (also SLIP) is
an encapsulation of the Internet Protocol designed to work
over serial ports and router connections.
On personal computers, SLIP has been largely replaced by
the Point -to - Point Protocol (PPP), which is better
engineered, has more features and does not require its IP
address configuration to be set before it is established

SOME TERMINOLOGIES USED IN NETWORK
What does Internet mean?
The internet is a globally connected network system that uses TCP/IP to transmit
data via various types of media.
The internet is a network of global exchanges – including private, public,
business, academic and government networks – connected by
guided, wireless and fiber-optic technologies.
The terms internet and World Wide Web are often used interchangeably, but they
are not exactly the same thing; the internet refers to the global communication
system, including hardware and infrastructure, while the web is one of the
services communicated over the internet.

Interspace is a client/server software program that allows multiple users
to communicate online with real-time audio, video and text chat in
dynamic 3D environments. Interspace provides the most advanced form of
communication available on the Internet today.
The Interspace is a vision of what the Internet will become, where users
cross-correlate information in multiple sources. It is an applications
environment for interconnecting spaces to manipulate information, much
as the Internet is a protocol environment for interconnecting networks to
transmit data.

Node or Workstations
Any system or device connected to a network is also called a node. For
example, if a network connects a file server, five computers, and two
printers, there are eight nodes on the network. ... This helps keep track of
where data is being transferred to and from on the network.

SERVER AND ITS TYPES
A server is a computer that serves information to other computers.
These computers, called clients, can connect to a server through either a
local area network (LAN) or a wide area network (WAN), such as the
Internet.
There are a number of different types of servers, including Web servers,
mail servers, and file servers.
A web server serves Web pages to computers that connect to it.
A mail server stores users' e-mail accounts and sends and receives e-mail
messages

TYPES OF SERVER
NON- DEDICATED SERVER DEDICATED SERVER
 A dedicated server is a single
computer in a network reserved for
serving the needs of the network.
For example, some networks
require that one computer be set
aside to manage communications
between all the other computers. ...
In the Web hosting business,
a dedicated server is typically a
rented service.

LAN (LOCAL AREA NETWORK)
LAN stands for Local Area Network is a group of network devices which allow the
communication between connected devices. The private ownership has the control over the local
area network rather than public. LAN has short propagation delay than MAN as well as WAN. It
covers the smallest area such as: College, School Hospital and so on.

MAN (METROPOLITAN AREA NETWORK)
MAN stands for Metropolitan Area Network. It covers the largest area than LAN such as:Small
towns, City etc. MAN connects 2 or a lot of computers that area unit apart however resides
within the same or completely different cities. MAN is expensive and should or might not be
owned by one organization.

WAN (WIDE AREA NETWORK)
WAN stands for Wide Area Network. It covers the large area than LAN as well as MAN such as:
Country/Continent etc. WAN is expensive and should or might not be owned by one organization.
PSTN or Satellite medium are used for wide area network.

LAN MAN WAN
LAN stands for Local Area Network.
MAN stands for Metropolitan Area
Network.
WAN stands for Wide area network.
LAN’s ownership is private. MAN’s ownership can be private or
While WAN also might not be owned by
one organization.
The transmission speed of LAN is high.
While the transmission speed of MAN is
average.
Whereas the transmission speed of WAN
is low.
The propagation delay is short in LAN.
There is moderate propagation delay in
MAN.
Whereas there is long propagation delay.
There is less congestion in LAN. While there is more congestion in MAN.
Whereas there is more congestion than
MAN in WAN.
LAN’s design and maintenance is easy.
While MAN’s design and maintenance is
difficult than LAN.
Whereas WAN’s design and maintenance
is also difficult than LAN as well MAN.
There is more fault tolerance in LAN. While there is less fault tolerance. In WAN, there is also less fault tolerance.

NETWORK TOPOLOGIES
The arrangement of a network which comprises of nodes and connecting lines
via sender and receiver is referred as network topology.
1. Bus Topology
2. Ring Topolgy
3. Star Topology
4. Extended Star Topology
5. Mesh Topology

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

BUS TOPOLGY (CONTD)
ADVANTAGES OF BUS TOPOLOGY
 Advantages of bus topology
 It works well when you have a small
network.
 It's the easiest network topology for
connecting computers or peripherals in a
linear fashion.
 It requires less cable length than a star
topology.
DISADVANTAGES OF BUS TOPOLOGY
 It can be difficult to identify the problems if
the whole network goes down.
 It can be hard to troubleshoot individual
device issues.
 Bus topology is not great for large
networks.
 Terminators are required for both ends of
the main cable.
 Additional devices slow the network down.

RING TOPOLOGY
In the Ring Topology, all the computers and networking devices are connected in a circular path or
closed loop. The last end of the network is connected to the first end. In the below figure, you can
see the diagram of the ring topology.

RING TOPOLOGY (CONTD)
ADVANTAGES
• Reduced chances of data collision as each
node release a data packet after receiving
the token.
• Token passing makes ring topology
perform better than bus topology under
heavy traffic
• No need of server to control connectivity
among the nodes
• Equal access to the resources
DISADVANTAGES
• n Unidirectional Ring, a data packet must
pass through all the nodes.
 Ex: Let’s say A, B, C, D, and E are a part of
the ring network. The data flow is from A
towards B and henceforth. In this condition,
if E wants to send a packet to D, the packet
must traverse the entire network to reach
D.
• Single point of failure, that means if a node
goes down entire network goes down.

MESH TOPOLOGY
A mesh topology is a network topology in which all the network nodes are
individually connected to most of the other nodes. There is not a concept of a
central switch, hub or computer which acts as a central point of
communication to pass on the messages.

MESH TOPOLOGY
ADVANTAGES
 Each connection can carry its own data
load
 It is robust
 A fault is diagnosed easily
 Provides security and privacy
DISADVANTAGES
•Installation and configuration are difficult if the
connectivity gets more
•Cabling cost is more and the most in case of a
fully connected Mesh Topology
•Bulk wiring is required

STAR TOPOLOGY
A star topology is a topology for a Local Area Network (LAN) in which all
nodes are individually connected to a central connection point, like a hub or a
switch. A star takes more cable than e.g. a bus, but the benefit is that if a cable
fails, only one node will be brought down.

STAR TOPOLOGY
ADVANTAGES
 Easy to install and wire.
 No disruptions to the network when
connecting or removing devices.
 Easy to detect faults and to remove
parts.
DISADVANTAGES
• Requires more cable length than a linear bus
topology.
• If the connecting network device (network switch)
fails, nodes attached are disabled and cannot
participate in network communication.
• More expensive than linear bus topology because
of the cost of the connecting devices (network
switches).

EXTENDED STAR OR TREE TOPOLOGY (STAR + BUS)
A Extended Star topology is a combination of a star network topology and a bus
topology. In tree topology, nodes of the underlying bus network topology are
replaced with a complete star topology.

EXTENDED STAR OR TREE TOPOLOGY
ADVANTAGES
 Point-to-point wiring for individual segments.
 Supported by several hardware and software
venders.
DISADVANTAGES
• Overall length of each segment is limited by the
type of cabling used.
• If the backbone line breaks, the entire segment
goes down.
• More difficult to configure and wire than other
topologies.

TRANSMISSION MEDIA
Transmission media is a communication channel that carries the information from the sender to
the receiver.
Data is transmitted through the electromagnetic signals.
The main functionality of the transmission media is to carry the information in the form of bits
through LAN(Local Area Network).
It is a physical path between transmitter and receiver in data communication.
In a copper-based network, the bits in the form of electrical signals.
In a fibre based network, the bits in the form of light pulses.

FACTORS NEED TO BE CONSIDERED FOR DESIGNING THE TRANSMISSION
TO BE CONSIDERED FOR DESIGNING THE TRANSMISSION MEDIA:
•Bandwidth: All the factors are remaining constant, the greater the bandwidth of a
medium, the higher the data transmission rate of a signal.
•Transmission impairment: When the received signal is not identical to the
transmitted one due to the transmission impairment. The quality of the signals will get
destroyed due to transmission impairment.
•Interference: An interference is defined as the process of disrupting a signal when it
travels over a communication medium on the addition of some unwanted signal.

GUIDED AND UNGUIDED TRANSMISSION MEDIA
 Guided transmission media are cables like twisted pair cables,
coaxial cables, and fiber optic cables.
 Unguided transmission media are wireless, such as infrared,
radio waves, and microwaves.
 Connectors are used to connect
the media with networking devices, and they are specific for
each transmission medium.

CLASSIFICATION OF TRANSMISSION MEDIA

TWISTED PAIR CABLE
Twisted pair cabling is a type of wiring in which two conductors of a
single circuit are twisted together for the purposes of improving
electromagnetic compatibility.

A STP (SHIELDED TWISTED PAIR)
 A STP (Shielded Twisted Pair) cable
has a fine wire mesh surrounding
the wires to protect the transmission
 Shielded cable is used in older
telephone networks, as well as
network and data communications
to reduce outside interference.

TWISTED PAIR CABLE
UNSHIELDED TWISTED PAIR CABLE (UTP)
 UTP stands for Unshielded Twisted Pair cable.
UTP cable is a 100 ohm copper cable that consists
of 2 to 1800 unshielded twisted pairs surrounded
by an outer jacket.
 They have no metallic shield.
 This makes the cable small in diameter but
unprotected against electrical interference.
 Unshielded twisted pair (UTP) cables are widely
used in the computer and telecommunications
industry as Ethernet cables and telephone wires.
 In an UTP cable, conductors which form a single
circuit are twisted around each other in order to
cancel out electromagnetic interference (EMI) from
external sources.

COAXIAL CABLE
Coaxial cable, or coax is a type of electrical cable that has an inner conductor surrounded by a
tubular insulating layer, surrounded by a tubular conducting shield. Many coaxial cables also have an
insulating outer sheath or jacket. The two types of Coaxial cable are Thicknet and Thinnet.
Applications. Coaxial cable is used as a
transmission line for radio frequency signals.
Its applications include feedlines connecting
radio transmitters and receivers to their antennas,
computer network (e.g., Ethernet) connections,
digital audio (S/PDIF), and distribution
of cable television signals.

OPTICAL FIBRE
An optical fiber is a thin fiber of glass or plastic that can carry light from
one end to the other. The study of optical fibers is called fiber optics,
which is part of applied science and engineering

FIBER OPTIC
A fiber optic cable is a network cable
that contains strands of glass fibers
inside an insulated casing.
They're designed for long distance, high-
performance data networking, and
telecommunications.
Compared to wired cables, fiber optic
cables provide higher bandwidth and can
transmit data over longer distances.

ADVANTAGES OF OPTICAL FIBER CABLE
Bandwidth
Fiber optic cables have a much greater bandwidth than metal cables. The amount of information
that can be transmitted per unit time of fiber over other transmission media is its most significant
advantage.
Low Power Loss
An optical fiber offers low power loss, which allows for longer transmission distances. In
comparison to copper, in a network, the longest recommended copper distance is 100m while with
fiber, it is 2km.
Interference
Fiber optic cables are immune to electromagnetic interference. It can also be run in electrically
noisy environments without concern as electrical noise will not affect fiber.
Size
In comparison to copper, a fiber optic cable has nearly 4.5 times as much capacity as the wire cable
has and a cross sectional area that is 30 times less.

ADVANTAGES OF OPTICAL FIBER CABLE (CONTD)
Weight
Fiber optic cables are much thinner and lighter than metal wires. They also occupy less space
with cables of the same information capacity. Lighter weight makes fiber easier to install.
Security
Optical fibers are difficult to tap. As they do not radiate electromagnetic energy, emissions
cannot be intercepted. As physically tapping the fiber takes great skill to do undetected, fiber is
the most secure medium available for carrying sensitive data.
Flexibility
An optical fiber has greater tensile strength than copper or steel fibers of the same diameter. It
is flexible, bends easily and resists most corrosive elements that attack copper cable.
Cost
The raw materials for glass are plentiful, unlike copper. This means glass can be made more
cheaply than copper.

USES OF FIBER OPTICS
•Internet. Fiber optic cables transmit large amounts of data at very high
speeds.
•Computer Networking.
•Surgery and Dentistry.
•Automotive Industry.
•Telephone.
•Lighting and Decorations.
•Mechanical Inspections.
•Cable Television.

WIRELESS COMMUNICATION TECHNOLOGY
Different Types of Wireless Communication Technologies
Wireless communication plays a significant role in day to day life. Besides
communication, wireless technology has become an integral part of our
daily activities.
The transmission of data or information from one place to another
wirelessly is referred as wireless communication.
This provides an exchange of data without any conductor through
RF and radio signals.
The information is transmitted across the devices over some meters to
hundreds of kilometres through well-defined channels.

TYPES OF WIRELESS COMMUNICATION
Different types of signals are used in communication between the devices for
wireless transmission of data. The following are the different electromagnetic
signals are used depending on their wavelength and frequency.
•Radio Waves (Radio Frequency Transmission – RF Waves)
•Satellite [Satellite Microwave Transmission]
•Microwave
•Infrared
•Laser

RADIO WAVES
Radio waves are a type of electromagnetic
radiation with wavelengths in the
electromagnetic spectrum longer than
infrared light.
The transmission making use of radio
frequencies is termed as radio-waves
transmission.
Any radio set up has two parts:
1. The transmitter
2. The receiver
The transmitter takes some sort of message
(it could be the sound of someone’s voice,
pictures )

WI-FI
Wi-Fi is the name of a popular wireless networking technology that uses radio
waves to provide wireless high-speed Internet and network connections.

HOW WI-FI NETWORKS WORKS
Wi-Fi networks have no physical wired connection between sender and receiver by
using radio frequency (RF) technology -- a frequency within the electromagnetic
spectrum associated with radio wave propagation.
When an RF current is supplied to an antenna, an electromagnetic field is created
that then is able to propagate through space.
The cornerstone of any wireless network is an access point (AP).
The primary job of an access point is to broadcast a wireless signal that computers
can detect and "tune" into. In order to connect to an access point and join a wireless
network, computers and devices must be equipped with wireless network adapters.

SATELLITE (MICROWAVES)
As you know that the radio wave can be classified by frequency and wavelength.
When frequency is higher than 3 GHz, then it is named microwave Satellite
communication is a special case of microwave relay system.
Satellite communication use the synchronous satellite to relay the radio signal
transmitted from the ground station.
Now-a-day, the use of wireless communication has gained more popularity.
Satellite and microwave communications network features the time saving, fast-
implementation and broad coverage characteristics, in comparison to the
traditional fixed wire terrestrial networks.
Satellite or satellite microwave communication provides voice, fax, data and
video services as well as email, file transfer,internet applications.

INFRARED COMMUNICATION
Infrared (IR) is a wireless mobile
technology used for
device communication over short
ranges. IR communication has
major limitations because it
requires line-of-sight, has a short
transmission range and is unable
to penetrate walls
Infrared – is used to transmit
information from remote controls.

LASER (LIGHT AMPLIFICATION BY STIMULATED EMISSION OF
RADIATION
In this laser communication system,
a laser beam is used as carrier, which is
modulated by the signal to be transmitted.
On the receiver end, the desired signal is
separated from the carrier. A
wireless laser link (through a laser diode)
is used to transmit information from one
end to another in its line of sight.

SWITCHING TECHNIQUES
Switching
A network consists of many switching devices. In order to connect
multiple devices, one solution could be to have a point to point
connection in between pair of devices. But this increases the
number of connection.
Hence a better solution for this situation is SWITCHING.
A switched network is made up of a series of interconnected nodes
called switches.

SWITCHING TECHNIQUES (CONTD)
There are basically three types of switching
methods are made available.
Out of three methods, circuit switching and
packet switching are commonly used but the
message switching has been opposed out in the
general communication procedure but is still
used in the networking application.
1) Circuit Switching
2) Packet Switching
3) Message Switching

CIRCUIT SWITCHING
Circuit switching is a method
of implementing a
telecommunications network in
which two network nodes
establish a dedicated
communications channel
(circuit) through the network
before the nodes may
communicate.

MESSAGE SWITCHING
Message switching is a network
switching technique in which data
is routed in its entirety from the
source node to the destination
node, one hope at a time.
During message routing, every
intermediate switch in
the network stores the
whole message
It has a store and forward
mechanism

PACKET SWITCHING
Packet switching is a digital network
transmission process in which data is
broken into suitably-sized pieces or
blocks for fast and efficient transfer via
different network devices.
When a computer attempts to send
a file to another computer, the file is
broken into packets so that it can be
sent across the network in the most
efficient way.
These packets are then routed by
network devices to the destination.

COMMUNICATION MODES
Transmission mode refers to the mechanism of transferring of data between
two devices connected over a network. It is also called Communication
Mode. These modes direct the direction of flow of information.
The three types of transmission modes are
1. Simplex
2. Half duplex
3. Full duplex.

SIMPLEX COMMUNICATION MODE
In this type of transmission mode, data can be sent only in one direction i.e. communication is
unidirectional.
We cannot send a message back to the sender. Unidirectional communication is done in Simplex
Systems where we just need to send a command/signal, and do not expect any response back
Examples of simplex Mode are loudspeakers, television broadcasting, television and remote,
keyboard and monitor etc.

HALF DUPLEX MODE
Half-duplex data transmission means that data can be transmitted in both directions on a signal carrier,
but not at the same time.
For example, on a local area network using a technology that has half-duplex transmission, one
workstation can send data on the line and then immediately receive data on the line from the same
direction in which data was just transmitted. Hence half-duplex transmission implies a bidirectional line
(one that can carry data in both directions) but data can be sent in only one direction at a time.
Example of half duplex is a walkie- talkie in which message is sent one at a time but messages are
sent in both the directions.

FULL DUPLEX MODE
In full duplex system we can send data in both the directions as it is bidirectional at the same
time in other words, data can be sent in both directions simultaneously.
Example of Full Duplex is a Telephone Network in which there is communication between two
persons by a telephone line, using which both can talk and listen at the same time.

MODEM
Modem is short for "Modulator-Demodulator."
It is a hardware component that allows a computer or
another device, such as a router or switch, to connect to the
Internet.
It converts or "modulates" an analog signal from a telephone
or cable wire to digital data (1s and 0s) that a computer can
recognize.
Similarly, it converts digital data from a computer or other
device into an analog signal that can be sent over standard
telephone lines.

TYPES OF MODEM
Modems come in two varieties
Internal Modem: The modems are fixed within the computer.
External Modem : The modems that are connected externally to a computer with other
peripherals.
The types of available modems include
1. Analog :
2. Digital subscriber line (DSL),
3. Cable and Integrated Services Digital Network (ISDN).
DSL and cable are high-speed broadband connections.

ETHERNET
Ethernet is a way of connecting computers together in a local area network or LAN. It has been the
most widely used method of linking computers together in LANs since the 1990s. The basic idea of
its design is that multiple computers have access to it and can send data at any time.
An example of Ethernet is the cable system that connects the computer network of a small business
office.
An Ethernet cable is a common type of
network cable used with wired networks. Ethernet
cables connect devices such as PCs, routers, and
switches within a local area network. These
physical cables are limited by length and durability

RJ - 45 CONNECTORS
RJ45 is a type of connector commonly used for Ethernet networking. It looks similar to a telephone
jack, but is slightly wider.
Since Ethernet cables have an RJ45 connector on each end, Ethernet cables are sometimes also
called RJ45 cables.
The "RJ" in RJ45 stands for "registered jack," since it is a standardized networking interface. The
"45" simply refers to the number of the interface standard.
Each RJ45 connector has eight pins, which means an RJ45 cable contains eight separate
wires. If you look closely at the end of an Ethernet cable, you can actually see the eight wires,
which are each a different color. Four of them are solid colors, while the other four are striped.

ETHERNET CARD
An Ethernet card in your computer serves one basic function: to transmit data from the network to
your computer.
Ethernet cards are physical expansion cards that insert into a PCI expansion slot on a computer.
Some computers also have onboard Ethernet cards that sit directly on a hard drive and perform the
same tasks as a PCI Ethernet card.

ETHERNET CARD(CONTD)
What the Card Does
An Ethernet card is the communications hub for your computer; it connects to a network using a network
cable.
Ethernet cards can also communicate one-on-one with another Ethernet card, allowing for peer-to-peer
network connections -- these are useful for direct file sharing.
The cable connection on the Ethernet card is called an RJ-45 connection, which connects to a variety of
cable types, all capable of different transmission speeds.

HUBS
A hub is a physical layer networking device which is
used to connect multiple devices in a network. They
are generally used to connect computers in a LAN.
A hub has many ports in it. A computer which intends
to be connected to the network is plugged in to one
of these ports. When a data frame arrives at a port,
it is broadcast to every other port, without
considering whether it is destined for a particular
destination or not.

TYPES OF HUBS
There are three basic types of hubs.
Passive Hub: This type of does not amplify or boost the signal. It does not manipulate or
view the traffic that crosses it. The passive hub does not require electrical power to work.
Active Hub: It amplifies the incoming signal before passing it to the other ports. It requires
AC power to do the task.
Intelligent Hub: They are also called as smart hubs. Function as an active hub and also
include diagnostic capabilities. Intelligent hubs include microprocessor chip and are very
useful in troubleshooting conditions of the network.
Hub is also called as concentrator because hubs serve as a central connection point for an
Ethernet Local Area Network.

SWITCHES
A switch is a data link layer networking
device which connects devices in a network
and uses packet switching to send and
receive data over the network.
Like a hub, a switch also has many ports, to
which computers are plugged in.
However, when a data frame arrives at any port
of a network switch, it examines the
destination address and sends the frame to
the corresponding device(s). Thus, it supports
both unicast and multicast communications.

DIFFERENCE BETWEEN HUB AND SWITCH
HUBS
 They operate in the physical layer of the
OSI model.
 It is a non-intelligent network device that
sends message to all ports.
 It primarily broadcasts messages.
 Transmission mode is half duplex.
 They generally have fewer ports of 4/12.
SWITCH
 They operate in the data link layer of the
OSI model.
 It is an intelligent network device that
sends message to selected destination
ports.
 It is supports unicast, multicast and
broadcast.
 Transmission mode is full duplex.
 The number of ports is higher – 24/48.

REPEATERS
A repeater is a network device that retransmits a received signal with more power and to an
extended geographical or topological network boundary than what would be capable with the
original signal.
A repeater is implemented in computer networks to expand the coverage area of the network,
repropagate a weak or broken signal and or service remote nodes.
Repeaters amplify the received/input signal to a higher frequency domain so that it is reusable,
scalable and available.
Repeaters were introduced in wired data communication networks due to the limitation of a signal
in propagating over a longer distance and now are a common installation in wireless networks for
expanding cell size.
Repeaters are also known as signal boosters.

BRIDGE
A bridge is a device that lets you link two networks together.
Bridge devices work at the data link layer of the Open System Interconnect (OSI) model,
connecting two different networks together and providing communication between them.
Bridges are similar to repeaters and hubs in that they broadcast data to every node.
However, bridges maintain the media access control (MAC) address table as soon as they
discover new segments, so subsequent transmissions are sent to only to the desired
recipient.
Bridges are also known as Layer 2 switches.

ROUTER
A router is a networking device that forwards data packets between computer networks.
Routers perform the traffic directing functions on the Internet.
When a data packet comes in on one of the lines, the router reads the network address
information in the packet header to determine the ultimate destination.

ROUTERS (CONTD)
What is a WiFi router and how does it work?
A wireless router connects directly to a modem by a cable.
This allows it to receive information from — and transmit information to — the internet.
The router then creates and communicates with your home Wi-Fi network using built-in
antennas.
As a result, all of the devices on your home network have internet access.
How does a router connect to the Internet?
• Connect the modem to the Internet port of the router using the Ethernet cable.
• Connect the computer to any of the LAN ports on the back of the router using a standard
Ethernet cable.
• Power on your modem.
• Power on your router.

GATEWAYS
A gateway is a hardware device that acts as a "gate" between two networks.
It may be a router,firewall,server or other device that enables traffic to flow in and out
of the network.
While a gateway protects the nodes within network, it also a node itself.
The gateway node is considered to be on the "edge" of the network as all data must
flow through it before coming in or going out of the network.
It may also translate data received from outside networks into a format
or protocol recognized by devices within the internal network.

WIRELESS VS MOBILE COMPUTING
Wireless communication is simply data communication without the use of a
landline.
This may involve a cellular telephone, a two way radio, a fixed wireless
connection, a laser, or satellite communications. Here the computing device is
continuously connected to the base network.
Mobile or "untethered" computing essentially refers to a device that is not
always connected to a central network.
This group of devices includes laptops, newly created smart phones and also
PDA's. These products may communicate with a base location, with or without, a
wireless connection

TECHNOLOGIES AND INTERFACES THAT ARE USED FOR WIRELESS
AND MOBILE COMPUTING.
1. GSM
GSM stands for Global System for Mobile communications, which is one of the
leading digital cellular systems. The GSM standard for digital cell phones was
established in Europe in the mid 1980's. GSM has now become the international
standard in Europe, Australia and much of Asia and Africa.
2. CDMACDMA stands for Code-Division Multiple Access and is a digital cellular
technology that uses spread-spectrum techniques to utilize different applications in
different areas.
3. WLL
WLL is short for wireless in a local loop. Mobile telephone is primarily meant to provide
telephony for people on the move. The telephone is meant to keep the person connected
while he or she is away from their home or office.

TECHNOLOGIES AND INTERFACES THAT ARE USED FOR WIRELESS
AND MOBILE COMPUTING (CONTD)
.
4. 3G and EDGE
It is a specification for the third generation of mobile communication technology.
3G is dedicated to providing increased bandwidth. So much so that it can deliver
384 Kbps on a slow moving device, 128 Kbps when located in a car and up to 2
Mbps when attached to a fixed device or application.

DIFFERENCES BETWEEN GPRS, EDGE, 3G, AND 4G, AND 5G
Before advancing, it should be known that 1G, 2G, 3G, 4G, 5G etc refers to
the different generations of wireless communication technology
characterized by having a defined range of speed.
GPRS(General Packet Radio Service)
GPRS is a packet-based* wireless communication service. It is a 2G
technology network that support a download speed of up to 114Kbps.
Limitation of GPRS is that GPRS data cannot be sent while a voice call is in
progress.

EDGE(Enhanced Data GSM Evolution)
GPRS and EDGE are both 2G technology but EDGE is significantly faster with a
download speed of up to 384Kbps. EDGE is sometimes called a 2.5G network as
it also has some characteristics of a 3G network but it doesn't satisfy the
specification.
3G
Introduction of 3G network made video calling and seamless streaming of video
possible, with download speed of up to 3.1Mbps.

4G LTE(Long Term Evolution)
LTE is a 4G communication standard that supports HD video streaming,
download speed as high as 299.6Mbps.
Summary
1G delivered analog voice.
2G introduced digital voice (e.g., CDMA).
3G brought mobile data (e.g., CDMA2000).
4G LTE ushered in the era of mobile Internet.
GPRS(114Kbps) < EGDE(368Kbps) < 3G(3.1Mbps) < 4G/LTE(299.6Mbps)

5G (5 TH GENERATION)
The fifth generation of cellular technology, 5G, is the next great leap in speed
for wireless devices. This speed includes both the rate mobile users can
download data to their devices and the latency, or lag, they experience
between sending and receiving information.
5G aims to deliver data rates that are 10 to 100 times faster than current 4G
networks. Users should expect to see download speeds on the order of
gigabits per second (Gb/s), much greater than the tens of megabits per
second (Mb/s) speeds of 4G.
For example, at gigabits per second data rates, you could potentially
download a movie to your phone or tablet in a matter of seconds. Those type
of data rates could enable virtual reality applications or autonomous driving

5G (CONTD)
Is 5G dangerous?
Although 5G may improve our day to day lives, some consumers have voiced
concern and potential health hazards. Many of these concerns are over 5G's use of
the higher energy millimeter-wave radiation.
Best Upcoming 5G Mobile Phones
HUAWE MATE 30 PRO 5G.
SAMSUNG GALAXY S10 5G.
HUAWEI MATE X.
VIVO NEX 3 5G.
XIAOMI MI MIX ALPHA.
LG V50 THINQ.

APPLICATIONS OF NETWORKING
•E-mail(Electronic mail).
SMS (Short Message
Service)
•Research.
•Downloading files.
•Discussion groups.
•Interactive games.
•Education and self-improvement.
•Social Networking Sites
•Electronic newspapers and magazines.
•Chat
•Video Conferencing
The most popular uses of the Internet are:

NETWORK SECURITY
Network security is any activity designed to protect the usability and integrity
of your network and data. It includes both hardware and software
technologies. Effective network security manages access to the network. It
targets a variety of threats and stops them from entering or spreading on
your network.
Protection methods
1. Authorization
2. Authentication
3.Encrypted Smart Cards
4.Bio Metric System
5. Firewall

NETWORK SECURITY
Cookies
Cookies are small files which are stored on a user's computer.
They are designed to hold a modest amount of data specific to a particular
client and website, and can be accessed either by the web server or the
client computer.

HACKERS AND CRACKERS
Hackers constantly seek further knowledge, freely share what they have
discovered, and never intentionally damage data.
A cracker is one who breaks into or otherwise violates the system integrity of
remote machines with malicious intent.
A security hacker is someone who explores methods for breaching defenses
and exploiting weaknesses in a computer system or network.

VIRUS (VITAL RESOURCES UNDER SEIGE)
VIRUS Full Form. The full form of the virus is Vital Information Resources
Under Seize. This virus is different from the biological virus. It affects the
computer without the knowledge of the user.
Computer Virus
A computer virus is a malicious program that self-replicates by copying
itself to another program. In other words, the computer virus spreads by itself
into other executable code or documents.
The purpose of creating a computer virus is to infect vulnerable systems,
gain admin control and steal user sensitive data. Hackers design
computer viruses with malicious intent and prey on online users by tricking
them.

TYPES OF VIRUS
1.File Virus : This type of virus infects the system by appending
itself to the end of a file. It changes the start of a program so that the
control jumps to its code. After the execution of its code, the control
returns back to the main program. Its execution is not even noticed.
It is also called Parasitic virus because it leaves no file intact but
also leaves the host functional.
2.Boot sector Virus : It infects the boot sector of the system,
executing every time system is booted and before operating system
is loaded. It infects other bootable media like floppy disks. These are
also known as memory virus as they do not infect file system.

TYPES OF VIRUS(CONTD)
Macro Virus : Unlike most virus which are written in low-level
language(like C or assembly language), these are written in high-level
language like Visual Basic. These viruses are triggered when a program
capable of executing a macro is run. For example, macro virus can be
contained in spreadsheet files.
Network Virus:
A network worm or virus has the ability quickly degrade the performance of
a network, totally disabling critical devices, programs and network
connections. They use protocols, e-mails, files and commands of computer
network to spread themselves on the network.

ANTIVIRUS SOFTWARE
Antivirus software, sometimes known as anti-malware software, is designed to
detect, prevent and take action to disarm or remove malicious software from your
computer such as viruses, worms and Trojan horses. It may also prevent or
remove unwanted spyware and adware in addition to other types of malicious
programs.

EXAMPLES OF ANTI- SOFTWARE
5 Best Antivirus Software
1.Bitdefender. Bitdefender is one of the best Antivirus program that offers both
free and paid solutions for the users.
2.Avast. Avast is known for its free antivirus solution that offers reliable
protection and fulfills all basic requirements of the users.
3.Malwarebytes Anti-Malware.
4.AVG AntiVirus.
5.Norton.

VIRUS PREVENTION
•Install Anti-Virus/Malware Software.
•Keep Your Anti-Virus Software Up to Date.
•Run Regularly Scheduled Scans with Your Anti-Virus Software.
•Keep Your Operating System Current.
•Secure Your Network.
•Think Before You Click.

CLOUD COMPUTING
Cloud Computing is the use of hardware
and software to deliver a service over a
network (typically the Internet).
With cloud computing, users can access
files and use applications from any device
that can access the Internet.
An example of a Cloud
Computing provider is Google's Gmail.

BENEFITS OF CLOUD COMPUTING
1.Infrastructure as a service (IaaS) and platform as a service (PaaS) .
2.Private cloud and hybrid cloud.
3.Test and development
4.File storage.
5.Disaster recovery.
6.Backup.

Introduction to Computer Networking

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