Networking and Telecommunications
SEE COMPUTER SCIENCE 2080
Communication
Communication
is sending and receiving information between two or more persons.
Telecommunication
Telecommunication
is a system of transmission of sounds, images, texts or data in the form of electronic
signals.
Data Communication
Data
communication is a process of transferring data electronically from one place
to other using different transmission mediums. Eg. E-Mail, Chat
and phone calls.
Components of Data Communication.
i)
Data ii)
Sender iii) Medium iv) Receiver v) Protocol
Protocol
Protocol
is a set of rules by which computers on the network communicate with each other.
E.g. TCP/IP, SMTP,
HTTP etc.
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
The
transmission mode in which transmission of data can take place in one direction
only is called simplex mode. E.g.: Newspaper, Radio and Television.
Half duplex mode
The
transmission mode in which transmission of data can take place in both
directions but only in one direction at a time is called half duplex mode. E.g.:
Wireless handset and walkie-talkie.
Full duplex mode
The
transmission mode in which data can be transmitted in both directions
simultaneously is called full duplex mode. E.g.: Telephone, Internet etc.
Bandwidth
Bandwidth
can be defined as the maximum volume of data that can be transmitted through a
communication system.
We can measure
bandwidth in digital devices by bits per second and in analog devices by cycles
per second or Hertz (Hz).
Transmission medium / Communication
Channel
Transmission medium is a
pathway that can transmit information from a sender to a receiver through wired
or wireless medium on a network.
The types of
communication medium are:
i) Guided Medium (Bounded or Wired)
ii) Unguided
Medium (Unbounded or Wireless)
Guided medium
The transmission media which comprises of cables or wires through which data is
transmitted is called guided medium. They are called guided since they provide
a physical channel from the sender device to the receiver device. The signal
travelling through these media are bounded by the physical limits of the
medium.
E.g.: twisted pair
cable, co-axial cable, fibre optics cable, etc.
Features of guided media
a)
Data
transmits through the physical cable or fixed path
b)
Data
transmission rate is higher.
Unguided medium
The transmission media
which transfer data in the form of electromagnetic waves that do not require
any cables for transmission is called unguided medium. These media are bounded
by geographical boundaries.
E.g.: radio wave,
microwave, infrared etc.
Guided VS Unguided Media
|
Guided Medai |
Unguided Media |
|
Guided media is a medium that sends signals through a
solid physical path. |
Unguided media is a medium that transmits signals through
free space. |
|
There is a specific direction to send signals. |
There is no particular direction to send signals. |
|
Used in wired transmission |
Helps wireless transmission |
|
Twisted pair, coaxial cable, and fiber optics |
Radio wave, microwave, and infrared |
Twisted pair cable
A pair of wires
twisted with each other is known as twisted pair cable. A set of four
pairs of twisted wires are bundled to form cable. These are the most common
medium for LAN. Wires are twisted with each other so as to reduce crosstalk (A disturbance
caused by electromagnetic interference, along a circuit or a cable pair).
Its types are: a) Unshielded Twisted Pair Cable b)
Twisted Pair Cable
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.
The
connectors used with co-axial cables are BNC, T-connectors and terminators in
bus topology.
10
Mbps is the maximum speed of
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.
It
is costlier to maintain, produce and install.
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.
Computer network
A computer network
means two or more computers connected with each other to share data, hardware,
software and other resources.
Advantages of computer network
a)
Computer in a network can access the network-connected
hardware devices like printers, disk drives, etc.
b)
Data in a network environment can be updated from any
computer. Updated data can be accessed by all computers on the network.
c)
Computers in a network system share different software
packages.
d)
Information
can be exchanged rapidly in computer network.
Disadvantages of computer network
a)
The
sharing of information may leak the privacy of other clients.
b)
The
networking cost is high
c)
If
hardware or software malfunctions, it affects the whole network.
d)
Data
and information may be stolen by computer hackers if the security of network is
not reliable.
Reasons of keeping computers on the
network
a)
To
share hardware devices like printers, scanners, hard disks etc.
b)
To
share data and information.
c)
To
share software resources.
d)
To
communicate with each other.
Hardware components of a computer network
(Elements of Network)
Physical parts and
devices used to connect computers in the network environment are called
hardware components. The hardware components of computer network are
a)
Computer
system (Server or Workstation) b) Network
connectors c) Network cables
d) NIC Card e) MODEM f) Hub g)
Bridge
h) Switch i) Router j)
Gateway k) Repeater
Server
A server is the
main computer that provides services, data and other resources to the other
computers in the network environment. Network operating software used by server
is Novell Netware, Linux, Unix etc. Different
types of servers are file server, print server, application server etc.
Workstation
Workstation
is a computer network that utilizes network resources. Network operating
software used by workstation are Windows 98, Windows XP etc.
Node
Each
computer or device of network is called node.
Router
Router is an intelligent device that
connects two different networks which uses the address for filtering and
forwarding the data as well as it has an ability to determine the best route
for destination.
Network Interface Card (NIC)
A
Network Interface Card (NIC) is the adapter through which the computer is
connected to the network. The function of NIC is to convert data into
electronic signals and transfer them through cables and vice-versa. The advantage is to present the platform
for a communication between the computers within a network.
Cable
Cables
are commonly used media of physical channel for transmitting data between
computers in network. Examples of cables are coaxial,
twisted pair and fiber optic cable.
Connector
Connector
is an interface between the NIC of the computer and the cable that passes data
between computers in network. Examples of
connectors are BNC used with coaxial cable, RJ 45 used with UTP cable, ST used
with fiber optic cable etc.
Hub
A
hub is a network device with multiple points or ports which acts as a central
point from where different computers and other devices are connected. It broadcasts all network data
across each connection.
Hub is mostly used in physical star topology.
Switch
A switch is a networking device that
has multiple connecting ports which is often used interchangeably with the
bridge.
Bridge
A bridge is a device that connects two or more similar types
of network which filters the data or inspects incoming signals and decides
whether to forward the signals or discard them.
Gateway
Gateway is an interconnecting device
that connects two dissimilar networks
Repeater
Repeater
is a device that amplifies the incoming signals, creates a copy of it and
transmits the signal on network.
MODEM
MODEM is a device
which is used to transfer the data of one computer to another computer using
telephone lines.
The role of MODEM
in data transmission is that it transfers data from one computer to another
through telephone line. It also converts the digital signal into analog and vice
versa.
Importance of MODEM
MODEM modulates
the digital codes of the computer into analog signal, which then can travel
through the telephone cable. At the receiving end the MODEM kept there will
demodulate the analog signal to digital codes, which can be then understood and
used by the receiving computer. In this way a MODEM makes the computer network
possible.
Modulation / Demodulation
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. The
process of translating analog signals from a phone line and converts then into
digital signals for the computer is known as demodulation.
Software components of a computer network
a)
Network
protocol
b)
Network
operating system
c)
Device
driver
Network operating system [PMT 2075K]
Network
operating system is a set of computer program that manages the resources on
network. E.g. Novell network, Microsoft Windows NT, Linux, Unix etc.
Device driver
Device driver is a
program that controls the functionality of the hardware device.
Types of Network
a)
LAN
(Local Area Network)
b)
MAN
(Metropolitan Area Network)
c)
WAN
(Wide Area Network)
LAN (Local Area Network)
A LAN is a type of
network which covers small area i.e. within a room, building, or short distance
by using cables or small wireless devices. It is controlled by a single
organization. It uses private connection media. E.g.: network in a school,
college or cyber cafe. The diameter is not more than a few kilometres. LAN
offers bandwidth of 10-100 Mbps.
MAN (Metropolitan Area Network)
A MAN is a type of
network which covers an entire city. It is controlled by single or group of
organization. It uses private or public connection media. E.g.: interconnection
between different branches on same branch and ISP providing internet services.
It offers a number of network services compatible with bandwidth from 128 kbps
to 1 Gbps.
WAN (Wide Area Network)
A WAN is a type of
network which connects two or more
computers generally across a wide geographical area such as cities, districts,
and countries. It is controlled by group of organization. It uses public
connections media like telephone lines, satellite links or microwave system to
connect several LANs and MANs. E.g.
internet. Data transmission in WAN is slower than LANs and WANs.
Network topology (LAN topology)
The
arrangement or connection pattern of computers or nodes and other devices of
the network is called network topology. The three basic topologies are bus
topology, ring topology and star topology
Bus topology
The network topology in which computers and other devices are arranged in
linear format which uses a common backbone or wire to connect all the computers
and devices is called bus topology.
Advantages of bus topology [SEE 2073]
a)
It
is easy to set up computers and other devices in bus topology, because all the
devices are connected through a single wire.
b)
It
requires fewer cable media, so it is cheaper than other topologies.
c)
It
is easy to add new node to the network.
d)
Failure
of one workstation does not affect other computers on the network.
Disadvantages of bus topology
a)
The
whole network system collapses if the cable or backbone is damaged.
b) The network slows
down if additional computers are connected.
c) The limited length
of the cable in a network may restrict to connect the workstation or devices.
d) It is difficult to
find fault in this network topology.
Ring topology [MF 2076]
The network
topology in which computers are connected in the shape of a circle without any
end points is called ring topology. Each workstation contains two neighbours
for communication or an input and output connections.
Advantages of ring topology
i) It is easy it
set up and configure.
ii) Each computer gets equal opportunity to access the network resources.
iii) It supports high data transmission rate.
iv) Performs
better than a star topology under heavy network load.
Disadvantages of ring topology
i)Failure of any
cable or single computers may affect the entire network.
ii) It is difficult to detect the errors.
iii) Adding/removing the devices affect the entire network.
iv) Much slower
than an Ethernet network under normal load.
Star topology
The network
topology in which all computers or other devices are connected through a
central device through a central device called hub or switch is called star
topology.
Advantages of star topology
i) Easy to set up and configure.
ii) Failure of single computer or cable doesn’t affect the entire network.
iii) It is easy to find the fault.
iv) It is easy to extend to network by attaching new devices to the central
devices.
Disadvantages of star topology
i) It requires
more cable in comparison of bus topology so it is more costly.
ii) Failure of central devices (hub or switch) break down the whole system.
Network architecture (Models of Computer
Network)
The arrangement of
the computers on the network which is based on the computing model is called network
architecture. Its types are
a)
Centralized
computing network
b)
Client
/ Server Network
c)
Peer
to Peer Network
A centralized
computing network is a network in which a central host computer performs data
processing and storage on behalf of clients. It is different from client server network as client server
network consists of at least one server and one or more client as well as
client server provides high security of data and other resources.
Client/server network
Client/ server network is a type of network architecture
that consists of at least one server and one or more clients or workstations,
where users do their work. It provides central security administration and the
network administrator is responsible for data security and other resources
management of the network.
Peer-to-peer network
Peer-to-Peer network is a group of computers, which function
both as servers and workstations to share data, information and other resources
of the network. It lacks centralized network administration, where the network
administrator needs to manage security on each computer. It provides no
reliable security and might put data in higher risks.
Client/server network Vs Peer-to-peer
network
|
Client/server
network |
Peer-to-peer
network |
|
There is a specific server and specific clients connected
to the server. |
Clients and server are not distinguished; each node act
as client and server. |
|
The client request for service and server respond with
the service. |
Each node can request for services and can also provide
the services. |
|
The data is stored in a centralized server. |
Each peer has its own data. |
|
The client-server are expensive to implement. |
Peer-to-peer are less expensive to implement. |
Internet is an interconnection of several thousands of
computers of different types belonging to the various networks all over the
world in order to share data and information. TCP/IP is the communication
protocol used by the internet.
Services of
internet
WWW (World Wide Web), E-mail (Electronic mail), FTP
(File Transfer Protocol),
IRC (internet Relay Chat), Search Engine, Telnet, E-commerce
Advantages of internet
a) It provides entertainment, such as movies,
music, and games.
b) It allows people to communicate with each
other from all over the world.
c) It makes it possible to shop for goods and
services from the comfort of your home.
d) It provides instant access
to a vast amount of information from all around the world.
Disadvantages of internet
a) Online addiction and
excessive screen time can have negative effects on mental and physical health.
b) The internet is full of viruses and malware that can damage
computers and steal personal information.
c) The internet is a major source of pornography, which can be
harmful to children and adults.
d) Online harassment and
cyberbullying can cause emotional suffering and harm to individuals.
Intranet
An intranet is a private computer network that uses
the internet protocol to securely share any part of information of an
organization. It is owned by a single organization or company. It can only be
used by the employees of the owned organization.
Extranet
An extranet is a computer network that allows
controlled access from outside for specific business or educational purposes.
E-mail (Electronic
Mail)
E-mail (Electronic mail) is one of the most popular services provided by the
internet which send messages from
one computer to another using the internet. E.g. xyz@gmail.com
Any four sites that provide e-mail services
are:
www.yahoomail.com, www.hotmail.com,
www.gmail.com,
www.outlook.com
Advantages of
E-mail
a)
It
allows to send and receive message across the world at very low cost.
b)
E-mail
is faster, cheaper, more reliable than traditional mail.
c)
The
image, sound, video and documents can be attached to e-mail message.
d)
Email
can be accessed from anywhere in the world.
Disadvantages of
e-mail
a) Minor mistakes in e-mail address may deliver the mail to wrong address.
b) Since it passes through a vast electronic network, it may be seized in
between.
c)
Without the internet, e-mail is not possible.
d)
Risk of messages getting lost or buried in overflowing inboxes.
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
A web browser is a software that allows users to access and view websites on
the internet.
Examples of
web browsers are Mozilla Firefox, Google chrome, Internet Explorer, opera etc.
Search engine
A search engine is
a tool that helps to find the information on the internet using keywords or
phrases. Examples of search engines are Google, Bing, Yahoo, ask.com
etc
Telnet
A telnet is a program that allows a user to log in to a remote computer on
internet as a user on that system.
FTP (File Transfer
Protocol)
File Transfer Protocol is the internet tool that allows the user to transfer
the file from one computer to another computer. It helps to transfer (download
or upload) files from one computer to another computer.
Uploading /
Downloading
Uploading refers to copying files or documents, programs or data from the user
computer to the internet server. Downloading refers to the copying files or
document or program or data from the internet server to the user computer.
IRC (Internet
Relay Chat)
Internet Relay Chat is one of the important services provided by the internet
which allows the user to communicate with other people in real time. For eg:
chatting on facebook.
WWW (World Wide
Web)
The World Wide Web (WWW) is a
system of interconnected web pages and documents on the internet that can be
accessed using a web browser.
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