Computer Network, Internet
and Social Networks
Ashis Talukder, Ph.D.
Associate Professor
Dept of MIS, University of Dhaka
Dr. Ashis Talukder, MIS, DU
1
Course Outline

Computer Network:


Network Topology


BUS, TREE, STAR, RING, MESH, HYBRID
Internet








LAN, MAN, WAN, Intranet Extranet, VPN, SAN
How to access internet and Web
Search Engine
IP Address
DNS
URL
HTTP
Social Networks in Education
E-learning sites and Apps
Dr. Ashis Talukder, MIS, DU
2
Computer Network
 Background of Network
 When there was no network
 Motivation
 Resource Sharing
 Resource
 Hardware
 Software
 Data/Information
Dr. Ashis Talukder, MIS, DU
3
Computer Network
 Definition:
 When a number of computers or devices are
interconnected in a single communication
system
 growth of number & power of computers is
driving need for interconnection
 also seeing rapid integration of voice, data,
image & video technologies
Dr. Ashis Talukder, MIS, DU
4
Network Components
 A network consists of the following
components:





Computers/other devices (mobile, tab…)
Network interface cards
Peripheral devices
Networking media
Network devices
Dr. Ashis Talukder, MIS, DU
5
History of Computer Network
Dr. Ashis Talukder, MIS, DU
6
History of Computer Network
Dr. Ashis Talukder, MIS, DU
7
Classification
 Depending
coverage:
upon
the
area
 Local Area Network (LAN)
 Metropolitan Area network (MAN)
 Wide Area Network (WAN)
Dr. Ashis Talukder, MIS, DU
8
LAN
Dr. Ashis Talukder, MIS, DU
9
LAN
 smaller scope
 Building or small campus
 usually owned by same organization
as attached devices
 data rates much higher
 switched LANs, eg Ethernet
 wireless LANs
Dr. Ashis Talukder, MIS, DU
10
LAN
 LANs make it possible for businesses that
use computer technology to locally share
files and printers efficiently, and make
internal communications possible.
 A good example of this technology is
“Computer Lab”.
 They tie data, local communications, and
computing equipment together.
Dr. Ashis Talukder, MIS, DU
11
LAN
Dr. Ashis Talukder, MIS, DU
12
LAN
 Some common LAN technologies are:
 Ethernet
 Token Ring
 FDDI
Dr. Ashis Talukder, MIS, DU
13
MAN
 ISP
 Cable Distribution Network
 Banks’ ATM Network
Dr. Ashis Talukder, MIS, DU
14
MAN
 Metropolitan Area Network
 A MAN is a network that spans a
metropolitan area such as a city or suburban
area.
 A MAN usually consists of two or more LANs
in a common geographic area.
 For example, a bank with multiple branches
may utilize a MAN.
Dr. Ashis Talukder, MIS, DU
15
MAN
Dr. Ashis Talukder, MIS, DU
16
MAN
middle ground between LAN and WAN
private or public network
high speed
large area
Typically, a service provider is used to
connect two or more LAN sites using private
communication lines or optical services.
 A MAN can also be created using wireless
bridge technology by beaming signals across
public areas.





Dr. Ashis Talukder, MIS, DU
17
WAN
 Network of the networks
(Internet)
Dr. Ashis Talukder, MIS, DU
18
WAN: Internet Architecture
Dr. Ashis Talukder, MIS, DU
19
WAN
 span a large geographical area
 rely in part on common carrier circuits
 alternative technologies used include:




circuit switching
packet switching
frame relay
Asynchronous Transfer Mode (ATM)
Dr. Ashis Talukder, MIS, DU
20
WAN
 WANs are designed to do the following:




Operate over a large geographically separated
areas
Allow users to have real-time communication
capabilities with other users
Provide full-time remote resources connected to
local services
Provide e-mail, World Wide Web, file transfer, and
e-commerce services
Dr. Ashis Talukder, MIS, DU
21
WAN
 Some common WAN technologies are:






Modems
Integrated Services Digital Network (ISDN)
Digital Subscriber Line (DSL)
Frame Relay
US (T) and Europe (E) Carrier Series – T1, E1, T3, E3
Synchronous Optical Network (SONET)
Dr. Ashis Talukder, MIS, DU
22
Storage Area Network
 A SAN is a dedicated, high-performance
network used to move data between servers
and storage resources.
 Because it is a separate, dedicated network,
it avoids any traffic conflict between clients
and servers.
 SAN technology allows high-speed serverto-storage, storage-to-storage, or server-toserver connectivity.
Dr. Ashis Talukder, MIS, DU
23
Storage Area Network
Dr. Ashis Talukder, MIS, DU
24
Storage Area Network

This method uses a separate network infrastructure that
relieves any problems associated with existing network
connectivity.

SANs offer the following features:

Performance – SANs enable concurrent access of disk or tape
arrays by two or more servers at high speeds, providing
enhanced system performance.

Availability – SANs have disaster tolerance built in, because
data can be mirrored using a SAN up to 10 kilometers (km) or
6.2 miles away.

Scalability – Like a LAN/WAN, it can use a variety of
technologies. This allows easy relocation of backup data,
operations, file migration, and data replication between systems.
Dr. Ashis Talukder, MIS, DU
25
Virtual Private Network (VPN)
 A VPN is a private network that is
constructed
within
a
public
network
infrastructure such as the global Internet.
 Using VPN, a telecommuter can access the
network of the company headquarters
through the Internet by building a secure
tunnel between the telecommuter’s PC and a
VPN router in the headquarters.
Dr. Ashis Talukder, MIS, DU
26
Virtual Private Network (VPN)
Dr. Ashis Talukder, MIS, DU
27
Virtual Private Network (VPN)
Benefits of VPN:

A VPN is a service that offers secure, reliable
connectivity
over
a
shared
public
network
infrastructure such as the Internet.

VPNs maintain the same security and management
policies as a private network.

They are the most cost-effective method of
establishing a point-to-point connection between
remote users and an enterprise customer's network.
Dr. Ashis Talukder, MIS, DU
28
Intranet

One common configuration of a LAN is an Intranet.

Intranet Web servers differ from public Web servers in
that the public must have the proper permissions and
passwords to access the Intranet of an organization.

Intranets are designed to permit access by users who
have access privileges to the internal LAN of the
organization.

Within an Intranet, Web servers are installed in the
network.

Browser technology is used as the common front end
to access information such as financial data or
graphical, text-based data stored on those servers.
Dr. Ashis Talukder, MIS, DU
29
Intranet & Extranet
Dr. Ashis Talukder, MIS, DU
30
Extranet
 Extranets refer to applications and services
that are Intranet based, and use extended,
secure access to external users or
enterprises.
 This access is usually accomplished through
passwords, user IDs, and other applicationlevel security.
 Therefore, an Extranet is the extension of
two or more Intranet strategies with a
secure interaction between participant
enterprises and their respective intranets.
Dr. Ashis Talukder, MIS, DU
31
Network Topology
 The geometric structure of the
interconnections among the
participating computers and
devices in the network.
Dr. Ashis Talukder, MIS, DU
32
Classification
1. BUS
2. Tree
3. Star
4. Mesh
5. Ring
6. Hybrid
Dr. Ashis Talukder, MIS, DU
33
Bus Topology
Dr. Ashis Talukder, MIS, DU
34
BUS
 Architecture:

each machine is connected
to a single cable called drop
cable through some kind of
connector Tap.

Each computer or server is
connected to the single
common shared bus cable,
called the backbone of the
bus topology network.

A terminator is required at
each end of the bus cable to
prevent the signal from
bouncing back and forth on
the bus cable.
Dr. Ashis Talukder, MIS, DU
35
BUS

used with multipoint medium

transmission propagates
throughout medium bidirectionally

heard by all stations

full duplex connection between
station and tap


need to regulate transmission


allows for transmission and
reception
to avoid collisions and hogging
terminator absorbs frames at end
of medium
Dr. Ashis Talukder, MIS, DU
36
Bus Topology
 Single cable connects all network nodes
without intervening connectivity devices.
 Difficult to troubleshoot, not fault-tolerant
 Works well for small networks
 Relatively inexpensive to implement
 Easy to add to it
Dr. Ashis Talukder, MIS, DU
37
Tree
 The tree topology is a
generalization of the bus
topology.
 The transmission
medium is a branching
cable with no closed
loops.
 The tree layout begins
at a point known as the
headend or root.
Dr. Ashis Talukder, MIS, DU
38
Tree

One or more cables start at
the headend, and each of
these may have branches.

The branches in turn may
have additional branches to
allow quite complex layouts.

Again, a transmission from
any station propagates
throughout the medium and
can be received by all other
stations.
Dr. Ashis Talukder, MIS, DU
39
Ring
 A closed loop of
repeaters joined by
point to point links,
called the backbone.
 Receive data on one
link & retransmit on
another
 links unidirectional
 stations attach to
repeaters
Dr. Ashis Talukder, MIS, DU
40
Ring
 data in frames

circulate past all stations

destination recognizes
address and copies
frame

frame circulates back to
source where it is
removed
 media access control
determines when a
station can insert frame
Dr. Ashis Talukder, MIS, DU
41
Star
 In the star LAN topology, each
station is directly connected to
a common central node.
 Typically, each station attaches
to a central node via two pointto-point links, one for
transmission and one for
reception.
 In general, there are two
alternatives for the operation of
the central node.
Dr. Ashis Talukder, MIS, DU
42
Star
 One approach is for the central node to
operate in a broadcast fashion.
 A transmission of a frame from one station to the node is
retransmitted on all of the outgoing links.
 In this case, although the arrangement is physically a star, it is
logically a bus: A transmission from any station is received by
all other stations, and only one station at a time may
successfully transmit.
 In this case, the central element is referred to as a hub.
Dr. Ashis Talukder, MIS, DU
43
Star
 Another approach is for
the central node to act as
a frame-switching
device.
 An incoming frame is
buffered in the node and
then retransmitted on an
outgoing link to the
destination station.
Dr. Ashis Talukder, MIS, DU
44
Mesh
 All the nodes are directly
connected to all other
nodes.
 Highly reliable with
alternative paths between
any pair of hosts
 Very good for short
distance communication
 The physical fully
connected mesh topology is
generally too costly and
complex for practical
networks

Not feasible for long haul
communication. Dr. Ashis Talukder, MIS, DU
45
Mesh

Dr. Ashis Talukder, MIS, DU
46
Hybrid Topology
Dr. Ashis Talukder, MIS, DU
47
Internet
 The Internet, sometimes called the information
superhighway, is a worldwide, publicly accessible
series of interconnected computer networks that
transmit data by packet switching using the
standard internet protocol (IP).
 It is a "network of networks" that consists of
millions of smaller domestic, academic, business,
and government networks, which together carry
various information and services, such as
electronic mail, online chat, file transfer, and the
interlinked web pages and other resources of the
world wide web (WWW)
Dr. Ashis Talukder, MIS, DU
48
Internet
 No one owns it.
 It has no formal management organization.
 As it was originally developed by the
Department of defense, this lack of
centralization made it less vulnerable to
wartime or terrorist attacks.
 To access the Internet, an existing network
need to pay a small registration fee and
agree to certain standards based on the

Transmission Control Protocol/Internet Protocol (TCP/IP).
Dr. Ashis Talukder, MIS, DU
49
Internet
 Common methods of home access include dialup, landline broadband (over twisted cable,
coaxial cable, fiber optic or copper wires), WiFi, satellite and 3G technology cell phones.
 Protocols
 Requires a common language to communicate
 Set of commands and timing specifications
 Transmission Communication Protocol (TCP)/ Internet
Protocol (IP)- unique address
Dr. Ashis Talukder, MIS, DU
50
How to access the Internet?
 To access the Internet, an existing network
need to pay a small registration fee and agree
to certain standards based on the TCP/IP
(Transmission Control Protocol/Internet
Protocol) reference model.
 Each organization pays for its own networks
and its own telephone bills, but those costs
usually exist independent of the internet.
 The regional Internet companies route and
forward all traffic, and the cost is still only that
of a local telephone call.
Dr. Ashis Talukder, MIS, DU
51
Internet Service Provider (ISP)
 A commercial organization with
permanent connection to the Internet
that sells temporary connections to
subscribers.
Dr. Ashis Talukder, MIS, DU
52
How to access the Web?
 Once you have your Internet connection, then
you need special software called a browser to
access the Web.
 Web browsers are used to connect you to
remote computers, open and transfer files,
display text and images.
 Web browsers are specialized programs.
Examples of Web browser: Mozilla Firefox,
Google chrome, Internet Explorer.
 Websites and Webpages: what are they?
Dr. Ashis Talukder, MIS, DU
53
Client/Server Structure of the Web
 Web is a collection of files that reside on
computers, called Web servers, that are
located all over the world and are connected to
each other through the Internet.
 When you use your Internet connection to
become part of the Web, your computer
becomes a Web client in a worldwide
client/server network.
 A Web browser is the software that you run
on your computer to make it work as a web
client.
Dr. Ashis Talukder, MIS, DU
54
HTTP
 The transfer protocol is the set of rules that the
computers use to move files from one
computer to another on the Internet.
 The most common transfer protocol used on
the Internet is the Hypertext Transfer Protocol
(HTTP).
 Two other protocols that you can use on the
Internet are the File Transfer Protocol (FTP)
and the Telnet Protocol
Dr. Ashis Talukder, MIS, DU
55
Finding information on the Web?
 A number of search engines (tools) have
been developed and available to you on
certain Web sites that provide search
services to help you find information.
 Examples:
 Google
 Yahoo


www.google.com
www.yahoo.com
Dr. Ashis Talukder, MIS, DU
56
IP Address
 Each computer on the internet does have a
unique identification number, called an IP
(Internet Protocol) address.
 The IPv4 addressing use 32 bit address,
contains four eight-bit block converted in
decimal numbers separated by a dot called
dotted-decimal format.
 Each part of the address is a number ranging
from 0 to 255, and each part is separated from
the previous part by period,
 For example, 106.29.242.17
Dr. Ashis Talukder, MIS, DU
57
Domain Name Services (DNS)
 Most web browsers do not use the IP address
to locate Web sites and individual pages.
 They use domain name addressing.
 A domain name is a unique name associated
with a specific IP address by a program that
runs on an Internet host computer.
 This program, which coordinates the IP
addresses and domain names for all computers
attached to it, is called DNS (Domain Name
Serice) software.
 The host computer that runs this software is
called a domain name server.
Dr. Ashis Talukder, MIS, DU
58
Domain Name Services (DNS)
 Domain names can include any number of parts
separated by periods, however most domain names
currently in use have only three or four parts.
 Domain names follow hierarchical model that you can
follow from top to bottom if you read the name from the
right to the left.
 For example, the domain name gsb.uchicago.edu is the
computer connected to the Internet at the Graduate
School of Business (gsb), which is an academic unit of
the University of Chicago (uchicago), which is an
educational institution (edu).
 No other computer on the Internet has the same domain
name.
Dr. Ashis Talukder, MIS, DU
59
Uniform Resource Locators (URL)
 To identify a Web pages exact location, Web
browsers rely on Uniform Resource Locator
(URL).
 URL is a four-part addressing scheme that
tells the Web browser:
 What transfer protocol to use for transporting the file
 The domain name of the computer on which the file
resides
 The pathname of the folder or directory on the
computer on which the file resides
 The name of the file
Dr. Ashis Talukder, MIS, DU
60
Uniform Resource Locators (URL)
Structure of a Uniform Resource Locators
pathname
protocol
http://www.chicagosymphony.org/civicconcerts/index.htm
Domain name
filename
http => Hypertext Transfer Protocol
Dr. Ashis Talukder, MIS, DU
61
Email Address
User ID
abcd@gmail.com
Domain Name
Domain Type
Domain ID
Dr. Ashis Talukder, MIS, DU
62
Social Networks
Dr. Ashis Talukder, MIS, DU
63
Social Networks
 Social networks are websites and apps that
allow users and organizations to connect,
communicate, share information and form
relationships.
 People can connect with others in the same
area, families, friends, and those with the
same interests.
 Social networks are one of the most important
uses of the internet today.
Dr. Ashis Talukder, MIS, DU
64
Social Networks
Dr. Ashis Talukder, MIS, DU
65
Social Networks in Education
 Social media can help to aid teachers in
communicating with students even when they
are outside of the classroom.
 Use of social media platforms can provide
students with unlimited resources and texts
from credible sources that they can utilize to
their advantage in essays, projects, and
presentations.
Dr. Ashis Talukder, MIS, DU
66
Social Networks in Education






Educational Benefits of Social Media
Easy sharing of Information
Social Credibility
Cost-effective Communication
Any time Connectivity
Sharing Information & Knowledge
Dr. Ashis Talukder, MIS, DU
67
Social Networks in Education





Today, many schools in India & education institutions are adapting these
developments into their frameworks and depending on group assets and systems
to improve the life of students.
The utilization of social media in education helps students, teachers, and parents
for getting more valuable information while connecting with learning groups and
other educational systems.
Social network sites & websites provide with lots of chances to improve their
techniques of learning & teaching to students and schools, respectively. Through
these networks, you can join social media modules or plugins that empower
sharing and collaboration.
Students can benefit themselves through online tutorial exercises through
YouTube. Online courses are also offered by colleges abroad through Skype and a
full cluster of assets that are shared through social communities.
All above mentioned points are the benefits of social media education in schools.
Going through above advantages, one can understand the importance of social
networking sites in the educational field in today’s world.
Dr. Ashis Talukder, MIS, DU
68
Social Networks in Education














Broadcasting Alerts and Updates Via a Facebook Page
Streaming Lectures Using a WhatsApp or Facebook Group
Turning Twitter into a Message or class board for updates
Using Instagram as a Photo Essay Platform
Hosting Discussions on a Class Blog
Treating Essays as Blogs
Creating a Specific Pinterest Board for the Class
Highlighting Social Links on the School Website
Sharing Photos and Videos from Events
Starting Facebook Groups Based on Interests
Social media as a job-hunting tool
Making use of Instagram for visual learning
Using video chat tools like Skype
Create Facebook groups for Alumni
Dr. Ashis Talukder, MIS, DU
69
E-learning: Sites and Apps
 Educational apps are like a bridge between
instructors and learners.
 Emerging automation technologies like artificial
intelligence and machine learning have further
made educational apps more engaging and
user-friendly.
 Moreover, in the COVID situation, the best elearning mobile apps for Android/iOS made
online learning easier and safe.
Dr. Ashis Talukder, MIS, DU
70
Educational Sites and Apps







Google Classroom
Khan Academy
10 Minutes School
Coursera
Udemy
Vedantu
Topper
Dr. Ashis Talukder, MIS, DU
71
Educational Sites and Apps
Dr. Ashis Talukder, MIS, DU
72
Advantage of E-learning Sites and Apps





Efficient learning: Educational applications facilitate students to learn
the subject in a more personalized way. It makes online learning more
interactive and efficient.
Flexibility in Learning: Students can grab knowledge and attend
lectures by sitting at the convenience of home. They can access the
app anywhere and at any time as per the student’s flexible timings.
Better Digital Communication: Education apps also help to maintain
a healthy relationship between parents and teachers. The apps allow
teachers to clarify parents’ queries regarding their pupil’s learning
progress.
Knowledge-oriented activities: Multipurpose educational apps allow
students to improve their skills on various subjects, aptitude, and
many other Knowledge-oriented activities.
Money-saving Process: Subscription charges of online learning apps
are much lesser than a student pay for instructors.
Dr. Ashis Talukder, MIS, DU
73
Advantage of E-learning Sites and Apps





Remote Learning: E-learning apps help students learn anytime, even
away from the classroom. They ensure faster learning and improve
students’ ability to grasp the topic more deeply.
Online resources: Mobile apps help students to access a manifold of
eBooks, online materials, and other subject-related pdf’s anytime they
want.
Entertainment: Top E-learning apps change the face of traditional
education. The best online learning apps transform topics into
games format to attract users. Thus, unlike sitting ideal for a long time
in the classroom, the apps enable students to learn more interest.
24/7 Availability: Educational apps always stay active and facilitate
students to log-in and start learning all the time.
Systematic Learning Way: The best online learning applications in
the USA & India ensure smart and systematic learning methods.
Dr. Ashis Talukder, MIS, DU
74
Question...???
Dr. Ashis Talukder, MIS, DU
75
Thank You
Dr. Ashis Talukder, MIS, DU
76