Data Communication/ Transmission and Computer Networks
Transcript of Data Communication/ Transmission and Computer Networks
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Data Communication/ Transmission and Computer Networks
What is data transmission?
Physical movement of data from one place to another place (Physical exchange of data) is called
data transmission.
What is data communication?
This is the meaningful exchange of information after the relevant receiver gets transmitted
information.
Elements of Data Communication
1 Sender / Source
2 Data Communication Medium
3 Receiver
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Data Transmission Media
There are 2 main types of media that transmit data from one place to another place.
(1) Guided Media
(2) Radiated Media / Unguided Media
(1) Guided Media
I. Twisted Pair Cable (TP)
a) Unshielded Twisted Pair (UTP)
b) Shielded Twisted Pair (STP)
II. Co - axial Cable
III. Fiber Optics Cable
I. Twisted Pair Cable (TP)
This cable can transmit data from 100m to 200m without any obstacle. The costs of
these are less. There are two types, one is UTP and the other is STP. The jacks RJ45 and RJ11
are used to connect these to any device. Generally these are named as telephone cables and
these cables are spun to minimize the destruction which is caused by outside magnetic fields. UTP
STP
II. Co - axial Cable Generally these are called Antenna cables. They transmit data far about 500m without
any obstacle. These are more expensive than TP cable and less than Fiber optics. These are
connected to any device by BNC connector and used for CCTV camera systems.
Conductor (copper)
Insulating Jacket
Outer Jacket
Conductor (copper)
Insulating Jacket
Outer Jacket
Pair Shield
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Conductor (copper)
Insulating Jacket
Outer Jacket (Outer Cylindrical Shell)
Shield Second Conductor
Fiber Core
Cladding
Outer Jacket
III. Fiber Optics Cable
These cables can transmit data far about 2km without any obstacle and price is more than the
other cables. This is the guided media with low resistance and the speed of data transmission
is highest. These are connected with ST and SC connectors and transmit data by reflecting
light. It is called light reflection.
(2) Radiated Media / Un guided Media
I. Radio Waves
II. Infrared light beams
III. Micro Waves
I. Radio Wave These types of waves are used for radio telecast and television transmission. And also
radio waves are used for Wi-Fi and blue tooth technologies.
II. Infrared light beam
These are used to transmit data to short distance and mostly used in remote controls.
Also these are used in wireless keyboard and wireless mouse.
III. Micro Wave
This is used for transmit data long distance and also used in satellite technology.
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Blue tooth
This technology transmits data far about 100m and uses radio waves. This is used in
mobile phones, Laptops, Notebooks, Tablet computers, etc…….
Wi-Fi
This technology transmits data far about 150m using radio waves. Commonly this is
used to get wireless internet facilities.
Wi – max
This can transmit data far about 10 km and this is used for WAN. And also it is used for data
transmission among telephone exchanges.
Data Transmission Types
1. Serial Data Transmission
2. Paralleled Data Transmission
Serial Data Transmission
This is introduced as the way of data transmission one by one through any data transmission
media. As the fewer amounts of media are needed for this, the expense is less. And this gets a long
time for data transmission the speed is low. This is suitable for long distance data transmission.
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Parallel Data Transmission
This is introduced as the way of data transmission parallel once through several data
transmission media. As more media is needed for this, the expense is more and the data
transmission speed is high. This is suitable for short distance data transmission.
Data Transmission Modes
The direction of data transmission' There are 3 types of data transmission modes.
1. Simplex Data Transmission
Transmit data to only one direction
Ex :- Television Transmission
Radio Transmission
Sender Receiver
2. Half Duplex Data Transmission
Transmit data both directions, but not simultaneously
Ex :- Wolki - Toki Conversation
Sender Receiver
3. Full Duplex Data Transmission
Transmit data both direction simultaneously
Ex :- Telephone Conversation
Video Conferencing
Online Voice Chat
Sender Receiver
Computer Networks
A computer network consists of two or more computers that are link in order to shire
resources (Printers, scanners, CD drive), exchange files or folders or electronic communication
(Online chat, Video conferencing) among users.
Classification of Computer Network
1. Classification of Computer Networks According to Geographical area
Local Area Network /LAN
Metropolitan Area Network /MAN
Wide Area Network/WAN
Medium
Medium
Medium
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Local Area Network (LAN)
A small area limited for a room, a house, a building, several buildings, a school or a campus
is called LAN. In such network mostly cables are used to connect the computers each other. So in
every computer, a Network Interface Card (NIC) can be seen. A LAN expands for several miles
occasionally. LAN can be seen in three types
Personal Area Network (PAN)
The connection of the digital devices around one person.
Home Area Network (HAN)
The connection of the computers in a house.
Campus Area Network (CAN)
The connection of the computers in an area such as campus.
Example for LAN: - Computer network in your school
Metropolitan Area Network (MAN)
The connection of the computers with same technology which expanded in a large city is
called MAN. Personal computers as well as LAN can be in such network.
Ex :- Network built by connecting branches in several places in Colombo city.
Wide Area Network (WAN)
The network spread in all over the world or in a country is called WAN. In such network to
connect the computers each other, under grounded cables or satellite technology is used. LAN,
MAN and personal computers can be in a WAN. The Internet is the best example for WAN.
Eg :- Internet, School net
2. Classification of Computer networks according to Relationship
Peer To Peer (P2P)
Client Server
Peer To Peer (P2P)
Every computer in this network has similar privileges. There’s not a main computer
(Server).
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Client Server
The connection of main computer that supplies a resource to the network (Server) and a
client that asks for a resource from the network is called as Client – Server network
Eg :- Internet
Network in a bank
3. Classification of computer Networks according to opening to the external environment
Intranet
Extranet
Internet
Intranet
A network that limited to selected people only
Eg :- A network limited to an office
Extranet
This is also an Intranet but it is open to the environment, protecting through the username
and password
Eg :- A computer network in a bank (ATM)
Internet
This is a common network open to anyone in the environment
Eg :- Internet
Advantages of Computer Networking Hardware resource can be shared between computers.
Electronic communication between uses. (Online Chat, Video Conferencing)
Files, Folders can be shared between users.
Duplicating data is avoided
Communication cost can be reduced
Server
Client 3
Client 2
Client 1
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Disadvantages of Computer Networking
Computer viruses can easily accessed to the computer
Doesn’t have security for files and software in the computer or network.
System open to the hackers
Network management can become difficult
Sometimes error in one computer or hardware it may cause to functioning of other
computer.
Network Topology
Physical layout of a computer network is called as its topology I. Main Topologies i. Star Network Topology ii. Ring Network Topology iii. Bus Network Topology II. Hybrid Topologies iv. Tree Network Topology v. Mesh Network Topology
i. Star Network Topology
In a star network topology all computers and other communication devices are connected
to a central point such as Hub, Switch or Central Host Computer. Such a network topology can
be prepared easily and low cost. The disadvantage of this network topology is when central
point is not functioning the whole network will be broken down.
ii. Ring Network Topology
In a ring network topology all communication devices are connected in a continuous Ring.
Such a network topology can be prepared easily and low cost. The disadvantage of this
network topology is the low speed of data transmission and also when one computer is not
functioning the whole network will be broken down. Only the computer which owns the token
transmits data and the data transmission is done to only one direction.
Node ^A physical device of a network (Computer
/Printer/Server)
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iii. Bus Network Topology
Such a layout can be created by connecting the computers to the common channel with the
help of byways. Here the obstacles for the data transmission are minimum. The main
disadvantage is the high expense for the preparation. The high expense for the common
channel is the reason. Also the depending of the whole network on the main cable is another
disadvantage.
Hybrid Topologies
iv. Tree Network Topology
This is a network like a tree with branches. This can be introduced as a developed stage of
star topology. Controlling separately only one branch is an advantage. However establishing
and maintaining the network is a difficult task.
Node
Terminator
Nodes
Common Channel
(Backbone Cable)
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v. Mesh Network Topology
This is a developed stage of Ring network topology. Creating and maintaining is very
complex. Data transmission speed is high.
Network Hardware / Communication Devices
Hub
This is the centralized device that connect all the
computers each other in Star and tree Topology. As this
device transmits the data obtained from a computer to all
the computers, there will be a bustling. It is a powerful
disadvantage. Also the security of the data and
information is minimum.
Switch
This is also used as centralized device to connect all he
computers in Star and Tree topology. When data transmit
through this device as the data transmits to only relevant
computer, the data transmission speed is high. Also the
security of the data and information is high.
Modem
(MOdulation and DEModulation)
A modem is a device that converts digital signal into analog (Modulation) and analog signal
into digital (Demodulation) There are 2 types of modem
i. Internal Modem
ii. External Modem
A
B
C
D
E
F
G
H
Hub
F to C
A
B
C
D
E
F
G
H
Hub
F to C >>
E to A >
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Analog Signal
Digital Signals
Bridge
Bridge is used to connect 2 or more similar
networks
Router
A major function of router is that chooses the beat route between networks that may have
multiple paths between them.
Repeater
Any electrical signal reaching the repeater from one segment, will be amplified and
retransmitted to the other segment.
Gateway
Gateway is used to connect 2 or more different network that used to different
technology.
LAN ISDN = Integrated Services Digital Network
Network Interface Card (NIC)
NIC provides the physical connection between the computers and computer cables of a
network
Digital
Signal
Analog
Signal
Modulation
Demodulation
ISDN Gateway
Bridge
0 0 0 0 0 0
1 1 1 1 1 1 1
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Common Network Elements Client
Server
Modem
Shared Resources
Communication Media
Hub
Switch
Internet The Internet is a collection of computers and computer networks. It was started in 70’s from
USA developing ARPANET (Advanced Research Project Agency) The Internet was introduced to
Sri Lanka in 1995. Internet is the world’s biggest Wide Area Network. The computers are
connected to the internet is resource full and therefore internet is a massive collection of
information.
In general terms of internet are collection of computers, networks, Hardware, Software and
people. The internet consists of web pages and web pages are developed using web language
(HTML, XML and PHP)
Layout of the Internet
Web
Server
Web
Server
Web
Server
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Needs to access to the Internet A Computer
A Modem
A Telephone Line (SL Telecom, Mobitel, Dialog, Suntel, Lankabel…etc)
A Web Browser/An Internet Browser (Software)
Microsoft Internet Explorer
Mozilla Firefox
Opera
Safari
Google chrome
Netscape Navigator
An Internet Service Provider (ISP)
Sri Lanka Telecom
Mobitel
Dialog
ITMIN
PAN Lanka
Eureka
Suntel
Lankabel
Lanka Internet
Internet Facilities (Advantages of the Internet)
Online Chat
Video conferencing
E-commerce
E-banking
E-learning
E-medicine (E-channelling)
Downloading
Uploading
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Disadvantages of the Internet Computer viruses can easily access to the computers through the Internet
Children mind are corrupted
Hacking
Doesn’t have security and can’t control
No owner for the Internet
Web Address
Uniform Resource Locater (URL)
http://www.host name. Sub level domain name. Top level domain name
Domain Name
Eg:-
http://www.google.com
http://www.doenets.lk
http://www.saman.kamal.com Host Name – Name of the website
Domain Name – Common sub name that can be used for many websites
Domain Name – Common top level name that can be used for many websites
IP Address (Internet Protocol Address)
IP address is the number which is to identify each node uniquely connected to the computer
network
EX 192.248.9.33
123.45.6.4
This IP address should be in four numbers.
Top Level Domain Names
com - Commercial
edu - Education
org - Organization
gov - Government
mil - Military
uk - United Kingdom
lk - Sri Lanka
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Protocol Common rule of a network is called as a protocol
Eg:- http - Hyper Text Transfer Protocol
ftp - File Transfer Protocol
pop - Post Office Protocol
smtp - Simple Mail Transfer Protocol
DNS Server (Domain Name Server)
Converting web address into IP address is done by the DNS server.
E-Mail E-mail is a sending message from one computer to another computer (One e-mail account to
another e-mail account) via internet. To use e-mail both sender and recipient should have e-mail
accounts. The message has to be typed in to e-mail software (Outlook express). The massage will
be sent to your e-mail service provider and will be saved in the user’s mail box. When the receiver
logs into the system the service provider sends the mail saved in the system and the receiver read
the mail and replies.
E-mail Address
Username @ email service . Sub level domain name. Top level domain name
providers
hostname
Eg:- [email protected]
Advantages of e-mail over normal post
1 High speed for anywhere of the world
2 Low cost for anywhere of the world
3 Video, Audio, Picture files can be attached
4 Security of the message
5 No paper are used