Networking and
Telecommunications - SEE COMPUTER SCIENCE 2080
Communication
The process of
sending and receiving data and information between two or more than two people
is known as communication.
Telecommunication
The transmission
of data and information from one place to another for the purpose of
communication is known as telecommunication. E.g. mobile phone, Internet phone,
television, landline, radio, etc.
Data
communication
Data communication
is the process of transferring data and information between computers and other
electronic devices. E.g. E-Mail,
Chat and phone calls
Components
of Data Communication
The five basic
components (data, sender, medium, receiver and protocol) are required to make
data communication.
Data (message) :
Data is to be communicated between sender and receiver.
Sender : Sender is
a device used to transfer data.
Medium: Medium is
a channel through which sender and receiver make communication.
Receiver: Receiver
is a device used to receive data.
Protocol: Protocol
is a set of rules followed by sender and receiver.
Data Transmission Mode
Data transmission
mode is the way of transmission of data from one location to another.
There are three
types of transmission mode:
i) Simplex mode
ii) Half duplex
mode
iii) Full Duplex
Mode
Simplex mode
Simplex
mode is the transmission of data and information that takes place in only one
direction. It is a unidirectional mode of data transmission.
Radio, newspaper,
television broadcasting, books etc. are examples of simplex mode.
Half duplex mode
Half-duplex
is the transmission of data and information that flows in both directions but
only one direction at a time.
Walky-talky and
wireless handset are examples of half-duplex mode.
Full duplex mode
Full duplex mode
is the transmission of data and information that flows in both direction
simultaneously on the transmission path.
Mobile and
landline phones are examples of full duplex mode.
Communication
Media / Transmission Media
A channel or path
through which data and information are transmitted between connected devices in
a network environment is called communication media.
The two main types
of communication media are:
1. Guided
(Wired/bounded) communication media
2. Unguided
(Wireless/unbounded) communication media
1.
Guided (Wired/bounded) Communication Media
The media which
uses cable or wire to transfer data and information among computers are called
guided communication media.
This is an easy,
fast and secure way to transfer data and information from one computer to
another.
The
three types of wire or cable are:
a. Twisted pair
Wire
b. Co-Axial Cable
c. Fiber Optic
Cable
2.
Unguided (Wireless/unbounded) Communication Media
Unguided
communication is a communication channel in which data and information
transferred between two devices without using wire or cable.
It uses radio
signal for receiving and transmitting electronic data.
The
three types of wireless communication are:
l Radio Wave
l Micro Wave
l
Satellite Communication
Twisted
Pair Wire
Twisted pair wire
is made of copper and a pair of wires are twisted together and insulated with
plastic.
This is also
widely used in landline telephone.
RJ-45 connector is
the most popular connector used in twisted-pair wire.
Wires are twisted
with each other so as to reduce crosstalk (A disturbance caused by electromagnetic
interference, along a circuit or a cable pair).
The two
types of twisted pair wire are:
i. UTP (Unshielded
Twisted Pair)
ii. STP (Shielded
Twisted Pair)
Unshielded twisted pair (UTP)
Unshielded twisted pair is a popular
type of cable that consists of two unshielded wires twisted around each other
which are used in telephone wiring and local area networks (LANs).
It is called unshielded because it
has no additional foil wrap, or shield.
RJ-45 connector is
commonly used with unshielded twisted pair.
Shielded twisted pair (STP)
Shielded
twisted pair is a type of copper telephone wiring in which each of the two
copper wires are twisted together and coated with an insulating coating.
The extra covering in shielded
twisted pair wiring protects the transmission line from electromagnetic interference.
D-shell connectors
are used with shielded twisted pair.
Co-axial cable
Coaxial (or “coax”) cable is a
common type of cable used for transmitting data over long
distances.
They are most commonly used to
transmit cable TV and Internet signals.
BNC and T
connectors are the most popular connector used in co-axial cable.
Fiber optic cable
Fiber optics cable is one of the costlier cables used in
data communication which uses light to carry a data signal through the cable.
The connectors used in fiber optics are Screw Mounted
Adaptors (SMA), Spring-loaded Twist (ST), SC and FC.
Radio wave transmission
The transmission
making use of radio waves through air is called radio wave transmission.
It provides low
bandwidth for data communication.
Radio, TV, cellular phones etc. uses
radio transmission in one form or another.
The radio waves can travel through
walls and through an entire building.
Depending upon the frequency, they
can travel long distance or short distance.
It does not require line of sight for data transmission
Microwave transmission
Microwave is a line-of-sight wireless
communication technology that uses high frequency beams of radio
waves to provide high speed wireless connections that can send and
receive voice, video, and data information.
Microwaves do not pass through
buildings. So, indoor receivers cannot be used effectively.
It provides higher
bandwidth for data communication.
It requires line of sight for data transmission.
Infrared transmission
Infrared Transmission is the
transmission of data or voice information over infrared (IR) light over short
ranges.
It requires line-of-sight and is
unable to break through walls.
Satellite
Communication
Satellite
communication is used to transfer information wirelessly worldwide after 1965.
It is an
artificial satellite placed in outer space for the purpose of
telecommunication, radio, television, Internet, etc.
Text, photo,
video, etc. can be transferred worldwide using satellite communication.
It is like
microwave relay stations in the space or sky.
Computer
Network
Computer network
is a group of two or more computers and devices connected to each other through
wired or wireless media to exchange data and information and share hardware,
software and other resources.
It can share
resources like scanner, printer, hard disk, operating system software,
application software, etc. within the networking computer.
Advantage
of Computer Network
1. A network
connected computers can share hardware devices such as scanner, printer, hard
disk, etc.
2. It can
communicate and share information all over the world through Internet.
3. Computer
network supports centralized administration.
4. Networking also
provides the facility of data and software backup system.
Disadvantage
of Computer Network
1. Computer
network can be route for computer virus and malware transmission.
2. Skilled
manpower is required to manage and operate computer network.
3. The initial
setup cost is very high to build computer network.
4. Cybercrimes are
originated from computer network.
The
services provided by computer network are
print service,
message service, application service, file service, database service, etc.
"Computer network reduces
the operation cost." Justify this statement.
Computer network reduces the operation cost as it allows to share
software and hardware in the network, so extra hardware or software copies is
not needed to install for each and every computer in the network.
Basic Elements of the Network
· Physical parts and
devices used to connect computers in the network environment are called
hardware components.
· The hardware
components of computer network are computer set, modem,
hub, NIC card, bridge, repeater, etc.
· The software
elements are NOS, Protocol and Device Driver
1. NIC
Card
NIC stands for
Network Interface Card which connects all computers in network.
It provides a port
on the back of system unit to connect a computer in network.
It controls flow
of data to and from computers in network environment.
2.
Connectors
Connectors are
used to connect communication media with network devices.
It provides data
communication through NIC card.
The
different types of connectors are:
l
RJ- 45 connector for UTP cable
l BNC connector for co-axial cable
l ST connector for fiber optics
cable
3. Hub
Hub is a network
connectivity device with multiple ports for connecting different computers on
network.
It connects
computers in star topology.
It broadcasts all network data
across each connection.
4.
Switch
Switch is a
network connectivity device which joins multiple computers together to share
information among them.
The selected
computer can get information through switch.
It works faster
than hub.
Hub Vs Switch
|
Hub |
Switch |
|
It is cheaper than switch. |
It is more expensive than hub. |
|
It transmits data slower than switch. |
It transmits data faster than hub. |
|
It broadcasts the information packets to all computer connected network. |
It transfers packets to only those selected computers connected in network. |
|
It has 4 / 12 ports |
It has 24 to 48 ports |
5.
Bridge
Bridge is a
network connectivity device that interconnects two computer networks having
similar protocol.
It inspects
incoming signals and decides whether to forward or discard it.
It connects
similar networks.
6.
Router
Router is a
network connectivity device that joins multiple wired or wireless networks
together.
Like a bridge,
router also inspects and forwards data among different networks having similar
protocol.
It is an
intelligent device that has ability to determine the best possible path for
data transmission.
7.
Gateway
Gateway is a
network connectivity device that interconnects two networks having dissimilar
communication protocols.
It is also called
protocol converters.
8.
Repeater
Repeater is a
network connectivity device that accepts weak signals and regenerates them and
after that sends the message on their way.
It makes possible
for long-distance data transfer. So it boosts the data signals that are
received from network.
9. MODEM
(Modulator and Demodulator)
MODEM is a device
which connects computers to ISP (Internet Service Provider) by the help of
telephone line or router device.
The MODEM which is
placed inside the CPU Casing is called internal modem. MODEM which is placed
outside the Casing is called an external modem.
Importance of MODEM
MODEM converts
analog signal to digital signal and vice - versa. The MODEM converts the computer's digital
signals into analog signals which are then transmitted across the phone line which
is called modulation phase and The MODEM receives analog signals from phone
line and converts into digital signals for the computer which is called
demodulation phase.
Modulation
The process of
translating digital signals of a computer to analog signals, which are then
transmitted across the standard telephone lines, is known as modulation.
Demodulation
The process of
translating analog signals from a phone line and converts then into digital
signals for the computer is known as demodulation.
Bandwidth
The amount of data
that can be carried from one point to another in a given time period is called
bandwidth.
We can measure
bandwidth in digital devices by bits per second (bps) and in analogue devices
by cycles per second (cps) or Hertz (Hz).
Network Operating
System (NOS)
Network operating
system is an important software which controls and manages computer network.
Novell Netware is
a popular NOS. Windows NT, Windows XP, Linux, Banyan Vinex, etc. are other
example of NOS.
The main
functions of NOS are:
l It helps to setup and install
network.
l
It allows administration to add or remove users from computer network.
l
It enables users to have access to network resources.
l It manages and controls all the
resources of computer network.
Protocol
A set of rules
followed for interconnection and communication between computers in a network
is called a protocol. So it is rules followed while sending and receiving
information using network software.
NCP (Network
Control Protocol) was the first protocol.
Some
common protocols are as follows:
l TCP/IP (Transmission Control
Protocol/Internet Protocol) is used in Internet.
l HTTP (Hypertext Transfer Protocol)
is used to transfer HTML documents in WWW.
l SMTP (Simple Mail Transfer
Protocol) is used in sending e-mail.
l POP (Post Office Protocol) is used
to retrieve e-mail from a mail server.
l
FTP (File Transfer Protocol) is used to transmitting files between computers.
Device driver
Device driver is a
program that controls the functionality of the hardware device.
Types of
Network
Computer network
can be classified according to its area covered.
The main three
types of computer network on the basis of geographical location (area covered)
are:
1. LAN (Local Area
Network)
2. MAN
(Metropolitan Area Network)
3. WAN (Wide Area
Network)
1. LAN
(Local Area Network)
Local Area Network
is a network limited within a small area like a room, a building, school,
college, etc. generally connected through wire media.
It can cover up to
one kilometre for transferring data and information between the computers.
It has high speed
data transfer capacity than MAN and WAN.
Computer in LAN
can be connected through wireless media and is referred to as WLAN (Wireless
Local Area Network).
Computer lab
networking and cyber networking are examples of LAN.
Features
of LAN (Local Area Network)
Coverage area is a
generally small geographical area such as room, building and few kilometers.
l LAN runs the multiple devices to
share a transmission medium.
l The different topology used mainly
bus and ring in LAN
l The communication quality is
better in LAN, the transmission error rate are low as compare to WAN
LAN supports a
variety of communications transmission medium such as an Ethernet cable (thin
cable, thick cable, and twisted pair), fiber and wireless transmission.
2. MAN
(Metropolitan Area Network)
Metropolitan Area
Network (MAN) is a network within the area like valley, city, metropolitan,
etc. connected through wire or wireless technology or media.
It covers more
area than LAN and less area than WAN.
It has high speed
data transfer capacity than WAN and is slower than LAN.
It is used in
medium size organization having various branches within city or valley.
Cable TV network
and telephone networks providing high-speed DSL lines are examples of MAN.
Features
of MAN (Metropolitan Area Network)
l Network size up to 50 km. It may
be as small as a group of buildings in a campus to as large as covering the
whole city.
l It is normally owned by single or
multiple organizations.
l It facilitates sharing of regional
resources.
l They provide uplinks for
connecting LANs to WANs and Internet.
3. WAN
(Wide Area Network)
Wide Area Network
is a network that is extended to a large area i.e. world in which computers are
connected through wireless technology or media as satellite communication. It
is the largest computer network.
Internet, 4G Mobile Broadband Systems and
satellite communication are the best examples of WAN.
Features
of WAN (Wide Area Network)
l It covers the whole world and
cannot be restricted to any geographical location. It uses satellite and
microwave communication.
l It is normally owned by multiple
organizations.
l
Communication links are provided by public carriers like telephone networks,
satellites, network providers, cable systems, etc.
l They have low data transfer rate
and high propagation delay so they have low communication speed.
Network
Architecture/Model
Network
architecture defines how the computer communicates and interacts with each
other on network.
The
three types of network architecture are:
1. Peer to Peer
Network
2. Client-Server
Network
3. Centralized
Network
1. Peer
to Peer Network
Peer to peer is a type
of network model where all nodes on the network have an equal relationship with
each other. It can share data, hardware and software with each other.
It is suitable for
a small area such as small offices, small room, building, etc.
It uses many
operating systems such as Windows 2000, Windows 8, Macintosh Operating System
etc., have built-in features to support peer to peer network.
Advantage
of Peer to Peer Network
l All resources and contentions can
be shared in this network.
l System administrator is not
required and each user can control their shared resources.
l The failure of one computer
doesn't affect the functioning of other peers.
Disadvantages
of Peer to Peer Network
l It is difficult for administrator
and control as resources are decentralized in this network.
l Security is very low in this
system.
l Data recovery or backup is very
difficult.
2. Client-Server
Network
The network model
where one or more powerful computers (servers) provide the different network
services and all other users of computer network (clients) access those
services to perform user's tasks is known as client-server network.
In such networks,
there exists a central controller called server.
A server is a
specialized computer that controls the network resource and provides services
to other computers in the network.
Novell Netware,
Windows NT, Linux, etc. are the common examples of an operating system of
client-server network.
Advantages
of Client-Server Network
l Centralized back up is possible in
client-server computer network.
l The use of dedicated servers also
increases the speed of sharing resources.
l Security is better in this network
as all the shared resources are centrally administered.
Disadvantages
of Client-Server Network
l It requires specialized servers
with large memory. This leads to an increase in the cost.
l The cost of network operating
system that manages the various clients is also high.
l It requires network administrator.
3.
Centralized Network
A centralized
network is a network model in which a central host computer performs data
processing and storage on behalf of clients.
·
The main computer is known as host or server computer.
·
Workstation is just used for input/output operations,
which has no processing capabilities and are connected to server or host
computer. Linux or UNIX operating system is used in centralized network.
Advantages
of Centralized Network
l It saves cost of installation of
network system.
l It secures all data and
information on host computer which works on IPOS (input process output system).
l Host Computer gives facilities
like Disk storage and software to workstation.
Disadvantages
of Centralized Network
l The malfunctioning of host
computer affects other workstation.
l It takes long time for data
processing.
l It is difficult to add more
workstation
Workstation
A
computer on a network that uses resources of the network is called workstation.
Node
Each
computer or device of network is called node.
Network Topology
(LAN Topology)
Network topology
is the cabling structure of interconnected pattern of computers in LAN.
The
three main types of topology are:
1. Bus Topology
2. Ring Topology
3. Star Topology
1. Bus
Topology
The type of
topology in which all nodes and network devices are connected to single cable is
called bus topology. Terminators are attached at the cable's start and end
points.
When it has
exactly two end points, it is called linear bus topology.
Advantages
of Bus Topology
l It is cost effective and cable
required is least compared to other network topology.
l It is used in small networks and
easy to understand.
l It is easy to expand networks.
Disadvantage
of Bus Topology
l Break/Failure in main cable will
make the whole network to malfunction.
l Heavy network traffic or increase
in nodes will degrade performance of network.
l Terminators are necessary at both
ends of the cable.
2.
Ring/Loop Topology
The type of
topology in which each computer is connected to another computer with the last
one connected to the first is called ring topology.
It uses fiber
optic cable to transfer data.
Each and every
computer has equal responsibilities.
Data is
transferred in a sequential manner.
Advantages
of Ring Topology
l In this topology all computers, in
close loop, act as a client or server to transfer the information.
l Transmitting network is not
affected by high traffic or by adding more nodes.
l
It is cheap to install or setup and expand.
Disadvantages
of Ring Topology
l It is difficult for
troubleshooting.
l In ring topology, adding or
deleting the computers disturbs the network activity.
l Failure of one computer disturbs
the whole network in this topology.
3. Star
Topology
The type of
topology which connects all nodes to central device called hub/switch through a
cable is called star topology.
It is probably the
most common topology.
Star topology can
be used with twisted pair, optical fiber and coaxial cable.
Advantages
of Star Topology
l It provides fast performance and
low network traffic.
l
It is easy to troubleshoot setup and modify.
l
The failure of one node has not affected the rest of the nodes.
Disadvantages
of Star Topology
l Hub and more wires are required,
so the cost of installation is high.
l The whole network is stopped when
the hub fails.
l The system crucially depends on
control device switch/hub. If it fails, entire network fails.
Internet
The worldwide
connection of computer networks that use TCP/IP protocols to communicate with
one another using wire or wireless media as well as network devices is called
the Internet.
Internet is a
network of networks.
History
of Internet
Internet was
originated in 1969 AD by ARPANET (Advanced Research Project Agency Network).
ARPANET provides
communication among various bodies of government which was developed by United
States Department of Defense.
In 1992 AD, the
Internet was openly used throughout the world.
In Nepal, Internet
service was started by Mercantile Company in 1994 AD.
Advantages
of internet
a) Internet has an endless
knowledge supply which anyone can access that too free of cost.
b) Selling and buying has
become so easy with the use of internet and it has helped millions to sell and
buy their goods online.
c) Internet has given us
E-Mail which is fast, secure and reliable mode of communication.
d) It makes easy to transfer
the file or information.
Disadvantages
of internet
a) Increasing virus threats
not only steals your sensitive data but also damages your computer.
b) People using too much of
internet get disconnected from the real world.
c) Pornography that can get in
the hands of young children too easily.
d) Addiction to online games
affects health leading to obesity and serious health issues.
Extranet
An extranet is a
private network that uses internet technology and the public telecommunication
system to connect more than one organization.
Intranet
An intranet is a
private computer network that uses the internet protocol to securely share any
part of information of an organization.
Services
of Internet
1. World Wide Web
2. E-mail
3. Telnet
4. FTP (File
Transfer Protocol)
5. Search Engine
6. IRC (Internet
Relay Chat)
7. Online Banking
8. E-commerce
1. World
Wide Web
World Wide Web was
developed by Tim-Berners-Lee in 1989 AD. It is also called the web.
The interlinked
collection of hypertext documents and multimedia content available on internet
is called WWW.
2. E-mail
(Electronic Mail)
E-mail is the most
widely used service on the Internet which sends and receives messages
electronically through the Internet. E.g. sarthak1@gmail.com
Advantages
of using E-mail
l It is the cheapest and fastest
means of communication.
l It is more reliable than postal
mail.
l E-mail can be accessed from any
part of the world at any time.
l Information can be shared
globally.
l We can send photos, songs, video
clips and other file with e-mail attachments.
l A single mail can be sent to
multiple people at a time.
Disadvantages of e-mail
·
The
recipient needs access to the internet to receive email.
·
Viruses are
easily spread through email attachments.
·
Minor
mistakes in e-mail address may deliver the mail to wrong address.
·
Since
it passes through a vast electronic network, it may be seized in between.
Any four
sites that provide e-mail services are:
3.
Telnet
Telnet is the
facility of Internet that allows user to use a remote computer through
Internet.
4. FTP
(File Transfer Protocol)
File Transfer
Protocol (FTP) is transmission of files between computers on the Internet.
File Transfer
protocol helps to transfer (download or upload) files from one computer to
another computer.
Uploading
Uploading refers
to the process of sending or transferring data (files, documents, images,
videos, etc.) from a local device, such as a computer or smartphone, to a
remote server or another device.
Downloading
Downloading is the
process of receiving or retrieving data (files, documents, images, videos,
etc.) from a remote server or another device to a local device.
5.
Search Engine
Search engine is
the communication program that searches documents on the basis of specified
keywords and returns a list of the web links that matches the keywords.
Google, Ask, Alta
Vista, Bing and Yahoo can search for files on WWW (World Wide Web).
6. IRC
(Internet Relay Chat)
IRC allows people
from all over the world to communicate in real-time. Real-time communication
means communicating with people in the immediate present time.
7.
Online Banking
Online banking is
also known as Internet banking or web banking which allows a user to conduct
financial transactions through Internet.
It offers
customers almost every service traditionally available through a local branch
including deposits, transfers, and online bill payments.
Online banking is
fast and efficient. Convenience is a major advantage of online banking.
8.
E-commerce
E-commerce is also
known as electronic commerce or Internet commerce which means buying and
selling of goods, products, or services through Internet.
Transaction of
money, funds, and data are also considered as E-commerce.
Online stores like
hamrobazar, alibaba, muncha, foodmandu, Amazon, Flipkart, Shopify, Myntra,
Ebay, Quikr, Olx, etc. are examples of E-commerce websites.
ISP (Internet Service Provider)
An Internet service provider (ISP) is an organization that
provides services for accessing and using the Internet.
World Link, Mercantile, Classitech, Vianet etc are the ISPs of Nepal.
Web browser
Web browser is a
computer program that access web pages and displays them on the user’s
computer.
E.g., Mozilla
Firefox, Google Chrome, Internet Explorer, opera etc.
