CSIT108 Module-2.ppt

Amity School of Business
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Computer Network

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What is a Network ?
• A Network is a Connected System of Objects or
People.
• Computer Network
– It is a Collection of Computers and Other
hardware devices connected together so that
network users can share hardware, software, and
data as well as electronically communicate with
each other.

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Uses of Computer Network
• Simultaneous Access
• Sharing of Peripheral Devices
• Streamlined Personal Communications
• Easier Backup Process

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Network Computer

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Advantages and Disadvantages of
Computer Network
• Advantages
– File Sharing
– Resource Sharing
– Increase Storage
Capacity
– Increase Cost
Efficiency
• Disadvantages
– Security Issue
– Rapid Spread of
Computer Virus
– Expensive Setup
– Dependent on
Main File Server

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Advantages of Computer Network
• File Sharing
– The major advantage of a computer network is
that is allows file sharing and remote file access.
For Example, A person sitting at one workstation
of a network can easily see the files present on
the other workstation, provided he is authorized
to do so. It saves the time which is wasted in
copying a file from one system to another, by using
a storage device. In addition to that, many people
can access or update the information stored in a
database, making it up-to-date and accurate.

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• Resource Sharing
– Resource sharing is also an important benefit of a
computer network. For example, if there are four
people in a family, each having their own computer,
they will require four modems (for the Internet
connection) and four printers, if they want to use
the resources at the same time. A computer
network, on the other hand, provides a cheaper
alternative by the provision of resource sharing. In
this way, all the four computers can be
interconnected, using a network, and just one
modem and printer can efficiently provide the
services to all four members.

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• Increased Storage Capacity
– As there is more than one computer on a network
which can easily share files, the issue of storage
capacity gets resolved to a great extent. A
standalone computer might fall short of storage
memory, but when many computers are on a
network, memory of different computers can be
used in such case. One can also design a storage
server on the network in order to have a huge
storage capacity.

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• Increased Cost Efficiency
– There are many software's available in the market
which are costly and take time for installation.
Computer networks resolve this issue as the
software can be stored or installed on a system or
a server and can be used by the different
workstations.

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• Security Issue
– One of the major drawbacks of computer networks
is the security issues involved. If a computer is a
standalone, physical access becomes necessary for
any kind of data theft. However, if a computer is
on a network, a computer hacker can get
unauthorized access by using different tools. In
case of big organizations, various network security
software’s are used to prevent the theft of any
confidential and classified data.
Disadvantages of Computer Network

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• Rapid Spread of Computer Virus
– If any computer system in a network gets
affected by computer virus, there is a possible
threat of other systems getting affected too.
Viruses get spread on a network easily because of
the interconnectivity of workstations. Such spread
can be dangerous if the computers have important
database which can get corrupted by the virus.

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• Expensive Setup
– The initial set up cost of a computer network can
be high depending on the number of computers to
be connected. Costly devices like routers,
switches, hubs, etc., can add up to the bills of a
person trying to install a computer network. He will
also have to buy NICs (Network Interface Cards)
for each of the workstations, in case they are not
inbuilt.

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• Dependency on Main File Server
– In Case the main File Server of a computer
network breaks down, the system becomes useless.
In case of big networks, the File Server should be
a powerful computer, which often makes it
expensive.

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Components of Computer Network

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Components of Network
(Networking Hardware)
To Establish a computer Network various hardware are
required ; To Connect multiple network together or to
connect a computer or network to the internet. Some of
the most common types of networking hardware's are :

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Component of Computer Network
 Network Interface Card (NIC)
 Modem
 Hub
 Switch
 Router
 WAP
Bridge
 Gateway
 Repeater
 Multiplexer
 Wi-Fi
 Bluetooth

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• Network Adaptor or NIC (Network interface
Card)
– It is used to connects the PC physically to the
Network in order to send outgoing data from the
PC and to receive all incoming data sent via network
to PC.
– To connect a PC to an Ethernet (IEEE802.3 i.e.
Institute of Electrical and Electronics Engineering)
network using twisted pair cabling with RJ 11
Connector and Ethernet network adaptor with RJ
45 Connector would be used.

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• Modem
– It is the term used for a device that connects a
computer to the internet.
– The name Comes form the term Modulation and
Demodulation.
– Modulation refers to converting digital signals to
analog form so they can be transmitted over analog
media such as telephone lines.
– Demodulation refers to the translation from analog
form back to digital form.

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There are various types of Modem used:
• Conventional dial-up modem
– Used to transmit and receive data via regular
telephone lines max speed is 56kbps.
• ISDN (Integrated Service Digital Network)
– Used to transmit and receive data via ordinary
telephone lines, but by combining signals its max
speed is up to 128kbps.
Router
Firewall

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• DSL (Digital Subscriber Lines)
– Used to transmit and receive data over standard
telephone lines.
– Use a technology that does not tie up your
telephone lines, so you can use the Internet and
make voice calls at the same time.
– Data transmission is much faster then Previous
one.
– It speed degrades as the distance get closer.

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• Cable Modem
– Used to connect a PC to a cable Internet Services
similar to a cable TV services, max speed around
1.5Mbps
• Satellite Modem
– Used to transmit and receive via a Personal
Satellite dish.
– It is little slower than both DSL and Cable
Transmissions, but they have the advantages to
being able to be used in rural areas.

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• HUB
– It is least sophisticated and transmit all data
received to all network nodes connected to hub.
Consequently, with a hub, the network capacity is
shared among the nodes.
• Switches
– A switch is “smarter” than a hub and offers more
bandwidth. A Switch identifies the device for
which the data is intended and sends the network
data to that node only.
– It allows each node on the network to use the full
capacity of the Network.

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• Routers
– Routers are even smarter-they pass data on to the
intended receipt only.
– They can plan a path through multiple routers to
ensure the data reaches its destination in the most
efficient manner possible.
– It used in LAN,MAN and Internet.
• Wireless Access Point
– It is a device that functions similar to a hub, but it
is used to connect wireless devices to a wired
network

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• Bridge
– A bridge is a device that connect two network
based on similar technology. Such as a LAN in one
city and a similar LAN in another.
– It can also be used to partition one large LAN in
to two smaller ones.
– It is a device that functions similar to a hub, but
it is used to connect wireless devices to a wired
network.
Computer 1 Computer 2 Computer 3 Computer 4
Computer 1 Computer 2 Computer 3 Computer 4
Bridge
LAN A
LAN B

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• Gateway
– A gateway is a device to connect two dissimilar
network, such as two networks using different
networking communications Protocols.
• Repeaters
– Devices that amplify signals along a network.
– Due to loss of signal strength it is often necessary
to use a repeater to boost the signal.
• Multiplexers
– Combines the transmissions from various devices
and sends them as one message.

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• Communication Protocols
– It is an agreed upon standard for transmitting
data between two devices on a network.
– Protocols specify how devices physically connect to
a network, how data is packaged for transmission,
how receiving devices acknowledge signals and how
errors are handled.
– Common Protocols Ethernet and Token Ring (wired
networks) Bluetooth and Wi-Fi (wireless) TCP/IP
and WAP (Internet)

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• Ethernet
– Most widely used in wired networking protocol
– Used in LANs
– Speed 10Mbps – 10Gbps
– Ethernet uses a set of procedures known as
CSMA/CD (Carrier Sense Multiple Access Collision
Detection)

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• Token Ring
– LAN protocol developed by IBM
– Used with ring networks
– Uses a packet – Token (data + address)
– Token carries data to recipient.
– If token is free, any computer can take it and
attach message to it and send it.
– Eliminates collision.
– Speed 4-16 Mbps

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• Wi-Fi
– Wireless Fidelity
– Developed in 1990s
– Standard for wireless networks in the home or
office and connecting to Internet.
– Connection to Internet via Hotspot – geographical
area covered by Wi-Fi wireless access point.
– Designed for medium range data transfers.
– Speed – 11 Mbps – 100Mbps

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• Bluetooth
– Wireless technology using radio waves frequency
band of 2.4GHz
– Designed for short range communication (less than
10 meters)
– Appropriate for communication between mobile
devices, computer and peripheral devices.
– Speed – upto 3Mbps
– Two Bluetooth enabled devices recognise each
other and establish a piconet.
– 8 devices can use the same piconet
– One device – Master and others slaves

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• TCP/IP
– Transmission Control Protocol / Internet Protocol
– Protocol for Internet developed in 1970s
• WAP (Wireless Application Protocol)
– Standard for delivering content to mobile devices,
smart phones and pagers.
– Uses cellular telephone network.
– Content can be web content, email
– Uses WAP enabled browser - microbrowser

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Types of Networks
• LAN (Local Area Network)
– It is a network that covers relatively small geographical
areas. Such as home, office building or school.
– Privately owned networks with in a campus or building of
up to a few kilometer in size
– The device on the network can be connected with
either wired or wireless communication media.
– It distinguished from other kinds of network by three
Characteristics - Their size, Their Transmission
technology and Their Topology.

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Local Area Networks
• A local area network is a computer
network across one building or site.
Fileserver
Printer
Work Station
Network Cable

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Peer to Peer Network
• This describes a very simple
network structure where
shared resources such as
printers are available but
where there are very few
other facilities.
• All computers on the
network have similar
specification and status.

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Client-Server Network
• This method of network organization requires one or
more servers to which a number of clients may obtain
services.
• The servers act as central resource managers for
the network.
• A star topology is often used for this form of
network.

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• MAN (Metropolitan Area Network)
– It is basically a bigger version of a LAN and
normally uses similar technology.
– The best known example of a MAN is the cable
television network available in many cities.
– It might cover a group of near by corporate
offices or a city and might be either private or
public.
– It support both data and voice.

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• WAN (Wide Area Network)
– This network covers a large geographical area,
often a country and continent.
– It consists of two or more LANs, which could be
relatively closer to one another or far apart.
– It may be publicly accessible, like the internet, or
may be privately owned and operated

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PAN (Personal Area Network)
• A personal area network (PAN) is a computer network used for
communication among computer and different information
technological devices close to one person. Some examples of
devices that are used in a PAN are :
– personal computers
– Printers
– fax machines
– Telephones
– PDAs
– scanners, and even video game consoles.
• A PAN may include wired and wireless connections between
devices. The reach of a PAN typically extends to 10 meters. A
wired PAN is usually constructed with USB and Firewire
connections while technologies such as Bluetooth and infrared
communication typically form a wireless PAN.

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VPN (Virtual Private Network)
• A virtual private network (VPN) is a computer network in
which some of the links between nodes are carried by open
connections or virtual circuits in some larger network (e.g.,
the Internet) instead of by physical wires. VPNs, for
example, can be used to separate the traffic of different
user communities over an underlying network with strong
security features.
• A VPN may have best-effort performance, or may have a
defined service level agreement (SLA) between the VPN
customer and the VPN service provider. Generally, a VPN
has a topology more complex than point-to-point.
• A VPN works by using shared public infrastructure while
maintaining privacy through security procedures.

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Network Topologies
• Bus Topology
• Star Topology
• Ring Topology
• Tree Topology
• Mesh Topology

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• Bus Topology
– It has no central hub.
– It consist of a central cable to which all network
devices are attached.
– It is similar to ring networks except that the ends
are not connected.

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Advantages and Disadvantages of Bus
Topology
Advantages Disadvantages
Easy to implement Limits on cable length and
Workstation numbers
Low Cost Difficult to isolate network
faults
It is best suited for
small networks.
A cable fault affects all
workstations
As the number of workstations
increase, the speed of the
network slows down

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• Star Topology
– It is a oldest topology for Computer Network
– It consists of a central device to which all the
computers and other devices in the network
connected, forming a star shape.
– It provide the facility of time –sharing i.e.
Centralized computing
HUB

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Star Topology
Easy to add new
workstations
The failure of the central hub
leads to the failure of the
entire network.
Due to its centralized
nature, the topology
offers simplicity of
operation
Hubs are slightly more
expensive than thin-Ethernet
Centralized network /hub
monitoring

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• Ring Topology
– It is a less common alternative to the star and bus
topology.
– It do not have central hub.
– The computer and other network devices are
connected in a ring formation from one device to
next.
– Data travels from one device to another around the
ring in one direction only using token passing.

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Advantages and Disadvantages of Ring
Topology
Cable failures affect limited
users
Costly Wiring
Equal access for all users Difficult Connections
Each workstation has full access
speed to the ring
Expensive Adaptor
Cards
As workstation numbers
increase performance diminishes
slightly

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• Tree Topology
– Also known as a 'Hierarchical topology‘.
– It is a combination of Star and Bus topology. A
typical scenario is: a file server is connected to a
backbone cable (e.g. coaxial) that runs through the
building, from which switches are connected,
branching out to workstations.

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Tree Topology
Point to point wiring for
individual segments
Overall length of each
segment is limited by the
type of cabling used
Supported by several
hardware and software
windows
If backbone line is breaks,
the entire segment goes
down
More difficult to configure
and wire than other
topologies

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• Mesh Topology
– In this topology only one possible path from one
node to another node. If any cable in that path is
broken, the nodes cannot communicate.
– It uses lots of cables to connect every node with
every other node.
– It is very expensive to wire up, but if any cable
fails, there are many other ways for two nodes to
communicate.

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Mesh Topology
The arrangement of the
network nodes is such that
it is possible to transmit
data from one node to many
other nodes at the same
time.
The arrangement where in
every network node is
connected to every other
node of the network, many
of the connections serve no
major purpose. This leads to
the redundancy of many of
the network connections.

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What is internet ?
• A network of networks, joining many
government, university and private
computers together and providing an
infrastructure for the use of E-mail,
bulletin boards, file archives, hypertext
documents, databases and other
computational resources
• The vast collection of computer networks
which form and act as a single huge
network for transport of data and
messages across distances which can be
anywhere from the same office to
anywhere in the world.

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history & evolution of internet
• The seeds of Internet were planted in 1969, when U.S. Department
of Defense sponsored a project named ARPANET (acronym for
Advanced Research Project of NETwork). The goal of this project
was to connect computers at different universities .
• The engineers, scientists , students and researches who were part
of this system, began exchanging data and messages on it.
• In mid 80’s another federal agency, the National Science Foundation
created a new high capacity network called NSFnet, which was more
capable than ARPANET.

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history & evolution of internet
• NSFnet allowed only the academic research on its network and not any kind
of private business on it. So many private companies built their own
networks, which were later interconnected along with ARPANET and
NSFnet to form Internet.
• It was inter networking i.e the linking of these two and some other
networks (i.e the ARPANET, NSFnet and some private networks) that are
named Internet.
• The original ARPANET was shut down in 1990, and the government funding
for NSFnet discontinued in 1995. But the commercial Internet services
came into picture, which are still running the Internet.

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internet
The Internet has made things simple. It can be used for
following:
•Direct Communications
•Online shopping
•Distance Education
•Banking
•Knowledge Base
•Travel
•Bill Payments….etc.

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Net anatomy
The Web physically consists of
personal computer, web browser
software, a connection to an
Internet service provider,
computers called servers that
host digital data, and routers
and switches to direct the flow
of information.

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Navigating the web
The Web is known as a client-server
system. The computer is the client; the
remote computers that store electronic
files are the servers. To visit the
website, enter the address or URL of
the website in the web browser.
Browser requests the web page from
the web server that hosts the requested
site. The server sends the data over the
Internet to the computer. The web
browser interprets the data, displaying it
on the computer screen.

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internet, intranet & extranet

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Intranet
• An intranet is a private computer network that uses
Internet Protocol technologies to securely share any part
of an organization's information or operational systems
within that organization.
• The term is used in contrast to internet, a network
between organizations, and instead refers to a network
within an organization. Sometimes the term refers only to
the organization's internal website, but may be a more
extensive part of the organization's information
technology infrastructure.
• It may host multiple private websites and constitute an
important component and focal point of internal
communication and collaboration.

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Characteristics of intranet
• An intranet can be understood as a private version of the
Internet, or as a private extension of the Internet confined
to an organization. An intranet is built from the same
concepts and technologies used for the Internet, such as
client-server computing and the Internet Protocol Suite
(TCP/IP).
– An intranet can be understood as a private version of the
Internet, or as a private extension of the Internet confined to an
organization.
– Intranets are generally restricted to employees of the
organization, extranets may also be accessed by customers,
suppliers, or other approved parties.
– An organization's intranet does not necessarily have to provide
access to the Internet. When such access is provided it is
usually through a network gateway with a firewall, shielding the
intranet from unauthorized external access.

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extranet
Extranet is a private inter-organizational information system
that uses internet protocols, network connectivity, and possibly
the public telecommunication system to securely share part of
an organization’s information or operations with suppliers,
vendors, partners, customers or other businesses.
• Connects the intranets of two or more companies in a
business alliance
• Also known as an extended intranet
• Alliances sometimes referred to as e-marketplaces
– Plays an important role in the global business strategy of
many companies
– Enables them to build alliances with vendors, suppliers,
and other organizations internationally

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internet, intranet & extranet
• INTERNET
– It is a global system of interconnected computer networks that
use the standardized Internet Protocol Suite (TCP/IP) to serve
billions of users worldwide.
• INTRANET
– It is a private network that uses Internet protocols to securely
share any part of an organization's information or operational
systems within that organization.
• EXTRANET
– It is a private network that uses internet protocols, network
connectivity, and possibly the public telecommunication system
to securely share part of an organization's information. An
extranet can be viewed as part of a company's Intranet that is
extended to users outside the company, usually via the Internet.

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Internet addressing
• Internet consists of a large number of computers
connected with each other, it requires a proper
addressing system to uniquely identify each computer in
the network. Each computer connected to the Internet is
associated with a unique number and or a name called
computer address.
• To access any WEB PAGES on a computer, you would
require the computer address

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Ip address
• An IP address is a unique number associated with each
computer making it uniquely identifiable within all the
computers connected to the Internet. This is a 32 bit
number and is divided into four octets such as 00001010
00000000 00000000 00000110.
• For human readability, it is represented in a decimal
notation, separating each octet with a period. The above
number would therefore be represented as 10.0.0.6.
• Each octet can range from 0-255, this IP addresses lie
between 0.0.0.0. to 255.255.255.255 .

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Domain naming system
• A Domain Name is a way to identify and locate computers
connected to the Internet. No two organisations can have
the same domain name.
• A domain name always contains two or more components
separated by periods called “dots: some example of
domain names are ibm.com, nasa.gov etc. One a domain
name has been established, “subdomains “ can be
created within domain . For example, the domain name of
or a large company could be “vni.com” and within this
domain, subdomain can be created for each of the
company’s regional offices. The structure for this is
hostname.subdomain.second-level-domain.top-level
domain.

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Domain naming system
• There are two types of domains – Geographic Domains
and Non-Geographic Domains
Non-Geographic Domains
– Com – commercial entities
– Edu – educational institutions
– Net – organizations directly involved in the
Internet operations, such as network
providers and network information
centers
Geographic Domains
– uk – United Kingdom
– In – India

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Uniform Resource Locator (URL)
• A URL defines address of a site on the Internet.
They define the global addresses of documents
and other resources on WWW.
• The first part of a URL indicates the protocol to
be used, while the second part specifies the
domain name or IP address where the resource
is located.
• Example http://mysite .com/index.html

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Web Browsers
A web browser is the software program
to access the World Wide Web, the
graphical portion of the Internet. The
first browser, called NCSA Mosaic, was
developed at the National Center for
Supercomputing Applications in the
early 1990s. The easy-to-use point-and-
click interface helped popularize the
Web. Microsoft Internet Explorer and
Netscape Navigator are the two most
popular ones.

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E-mailing
• Electronic mail (E-mail) is an electronic message transmitted
over a network from one user to another. Email is a text-based
consisting of lines of text, and can include attachments such as
audio messages, pictures and documents. The features of e-mail
are as follows:
• E-mail can be sent to one person or more than one person at
the same time.
• Communicating via e-mail does not require physical presence
of the recipient. The recipient can open the e-mail at his /her
convenience.
• since message are transmitted electronically, e-mail is a fast
way to communicate with the people in your office or to people

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Internet Protocols
• Internet Protocols are required to transfer data over networks and
/ or the Internet in an efficient manner. When various computers
are connected through a computer network, it becomes
necessary to use a protocol to efficiently use network bandwidth
and avoid collisions.
• A network protocol defines languages that contains rules and
conventions for reliable communication between different devices
over the network.
• There are a number of Internet protocols used. The most
commonly used protocols are:
- Transmission Control Protocol / Internet Protocol (TCP/IP)
- HyperText Transfer Protocol (HTTP)
- File Transfer Protocol (FTP)
- Telnet

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Transmission Control Protocol / Internet
Protocol
It is a protocol suite used to transfer data over the Internet. Two
main protocol in this suite are :
• TCP: It divides a message or a file into smaller packets that are
transmitted over the Internet. These packets are received by a TCP layer
on the other side, which then re-assembles the data packets into original
message.
• IP : Handles the address part of each packet so that it is delivered to the
right destination. Usually, each gateway computer on the network checks
this address to identify where to forward the message. This implies that
all the packets of a message are delivered to the destination regardless of
the route used for delivering the packets.

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HyperText Transfer Protocol (HTTP)
• HTTP is a networking protocol for transferring files (text,
image, sound, video and other multimedia files) using the
Internet.
• Its defines how messages are formatted and transmitted and
what actions Web servers and Web browsers should take in
response to the commands issued.
• HTTP is based on Client/server architecture where Web
browser acts as a HTTP client making requests to the Web
server machines while an application running on a computer
hosting a web site function act as server.
• HTTP is a stateless protocol, which means each request is
processed independently ,without any knowledge of the
previous request.

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File Transfer Protocol (FTP)
• FTP is an application protocol for exchanging files
between computers over the Internet. It is the simplest
and most commonly used protocol for downloading
/uploading a file from / to a server.
• FTP also works on a client /server architecture where an
FTP client program is used to make a request to an FTP
server

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Telnet
• Telnet services enable an Internet user to log into another computer on
the Internet from his/her local computer. That is a user can execute the
telnet command on his/her local computer to start a login session on a
remote computer. This action is also called “remote login”.
• To start a remote login session, a user types the command telnet and
address of the remote computer on his/her local computer terminal. Then
system asks the user to enter a login name and a password. That is the
remote computer authenticates the user to ensure that he/she is
authorized to access it.
• If the user specifies a correct login and password, he /she is logged on to
remote computer, once login session is established with remote
computer, telnet enter input mode and anything typed on the terminal of
the local computer by the user is sent to the remote computer for
processing.

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Internet Services
• Internet Service Providers (ISPs)
• Internet Content Providers
• World Wide Web
• Application Service Providers (ASPs)

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Internet Service Provider
• An Internet service provider (ISP), also sometimes referred to
as an Internet access provider (IAP), is a company that offers its
customers access to the Internet typically for a fee. The ISP
connects to its customers using a data transmission technology
appropriate for delivering Internet Protocol Paradigm, such as
dial-up, DSL (Digital Subscriber Line is a broadband connection
that allows connecting to Internet over the existing telephone
lines.), cable modem, wireless or dedicated high-speed
interconnects.
• ISPs may provide Internet e-mail accounts to users which allow
them to communicate with one another by sending and receiving
electronic messages through their ISP's servers

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Internet Content Providers
Internet content providers supply the information that is available
through the Internet. Internet content providers can be commercial
businesses, nonprofit organizations, educational institutions, and more.
Some examples of Internet content providers are listed below:-
a) A photographer who posts samples of her best work on a web
page.
b) A political action group that sponsors an online forum for
discussions about topics that interest its members.
c) An individual who publishes his opinion on various subjects to an
online journal.
d) A software company that creates a Web site to provide
information and software downloads.
e) A national newspaper that maintains an online site to provide up-
to-the-minute news, feature stories and video clips.

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World Wide Web
• WWW (also called as Web) is a large scale, online store of
information. It is a system of creating, organizing and linking of
documents. Information is stored on WWW as a collection of
documents that are interconnected with each other via links. The
interconnected documents may be located on one or more than one
computer, worldwide, thus, the name world wide web. The features
of WWW and terms linked to WWW are given below:-
• The documents on web are created in hypertext format. Hypertext
facilitates linking of documents.
• The language used to create a hypertext format document is
HyperText Markup Language.
• The hypertext format document is transferred on the Web using
Hypertext Transfer Protocol (HTTP)
• A single hypertext document is called a Web page.

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World Wide Web
• A group of related web pages is called a Web site.
• A first web page or main page of a website is called Home
page.
• The web pages are stored on the Internet on the Web Server.
• Web Servers are host computers that can store thousands of
web pages.
• The process of storing a web page on a web server is called
uploading.
• The process of retrieving a web page from a web server onto
the user’s computer is downloading.
• The web pages stored on web sever on the Internet, can be
viewed from the user’s computer using a tool called Web
browser.

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World Wide Web
• Every web page is identified on Internet by its address , also
called Uniform Resource Locator (URL)
• A web portal is a web site that presents information from
different sources and makes then available in a unified way. A
web portal enables the user to reach fir any type of information
from a single location. i.e. the home page of the web portal. A
web portal generally consists of a search engine,
advertisements and an extensive lists of links to other sites etc.
www.google.co.in are popular web portals.

81
Application Service Providers (ASPs)
Application service providers (ASPs) are companies that manage and
distribute software-based services to customers over the Internet. Instead
of providing access to the Internet like ISPs do, ASPs provide access to
software applications via the Internet.
In essence, ASPs rent access to software programs to companies
or individuals- typically, customers pay a monthly or yearly fee to use
each application.
The advantages to using an ASP over buying software outright include
less up-front cost and the ability to try out a software program without
potentially wasting money purchasing software that might not fit the
customer’s needs. In addition, all users see the most up-to-date software
each time they use the application, since the software is located on the
ASP’s server and can be updated as needed.

82
VOIP
• Short for Voice over Internet Protocol, a category of hardware and
software that enables people to use the Internet as the transmission
medium for telephone calls by sending voice data in packets using IP
rather than by traditional circuit transmissions of the PSTN(public
switched telephone network).
• One advantage of VoIP is that the telephone calls over the Internet do
not incur a surcharge beyond what the user is paying for Internet
access, much in the same way that the user doesn't pay for sending
individual e-mails over the Internet.
• There are many Internet telephony applications available. Some, like
CoolTalk and NetMeeting

83
Video conferencing
• A videoconference or video conference (also known as a
videoteleconference) is a set of interactive telecommunication
technologies which allow two or more locations to interact via two-way
video and audio transmissions simultaneously. It has also been called
'visual collaboration' and is a type of groupware.
• Videoconferencing uses telecommunications of audio and video to bring
people at different sites together for a meeting. This can be as simple as
a conversation between two people in private offices (point-to-point) or
involve several sites (multi-point) with more than one person in large
rooms at different sites.

84
Instant messaging
• Instant messaging (IM) is a form of real-time direct text-based
communication between two or more people using personal computers
or other devices, along with shared software clients. More advanced
instant messaging software clients also allow enhanced modes of
communication, such as live voice or video calling.
• IM allows effective and efficient communication, allowing immediate
receipt of acknowledgment or reply. In many cases instant messaging
includes additional features which can make it even more popular. For
example, users can see each other by using webcams, or talk directly
for free over the Internet using a microphone and headphones or
loudspeakers.

85
Chat room
• Chat room is a part of a Web site, or part of an online
service such as America Online, that provides a venue for
communities of users with a common interest to
communicate in real time. Forums and discussion groups, in
comparison, allow users to post messages but don't have
the capacity for interactive messaging.
• Chat room users register for the chat room of their choice,
choose a user name and password, and log into a particular
room (most sites have multiple chat rooms).

86
Online shopping
• Online shopping is the process whereby consumers directly buy goods
or services from a seller in real-time, without an intermediary service,
over the Internet. If an intermediary service is present the process is
called electronic commerce. An online shop, eshop, e-store, internet
shop, webshop, webstore, online store, or virtual store.
• When a customer buys from company its called Business-to-Consumer
(B2C) online shopping. When a business buys from another business it
is called Business-to-Business (B2B) online shopping. Both B2C and
B2B online shopping are forms of e-commerce.

87
Online auction
• Online auction is virtual auctions on the internet. The seller
sells the product or service to the person who bids the
highest price. For sellers, online auctions open up new
sales channels for new products and offer buyers favorable
purchasing conditions.
• Online auctions have effectively created a giant virtual
marketplace where people can gather to buy, sell, trade and
check out the goods of the day.

88
E-book
• An e-book (short for electronic book) is “a portable
electronic device used to download and read books or
magazines that are in digital form.
• E-books are usually read on dedicated hardware devices
known as e-Readers or e-book devices. Personal
computers and some cell phones can also be used to read
e-books.

89
E-book
• An e-book (short for electronic book) is “a portable
electronic device used to download and read books or
magazines that are in digital form.
• E-books are usually read on dedicated hardware devices
known as e-Readers or e-book devices. Personal
computers and some cell phones can also be used to read
e-books.

90
• The Internet is free
– This myth stems from the fact that there has traditionally
been no cost associated with online content – such as
news and product information – or e-mail exchange,
other than what the internet users pay their ISPs for
internet access. Many people – such as students,
employees, and consumers who opt for free internet
service or use free access available at public libraries ot
other public locations – pay nothing for internet access.
– Businesses, schools, public libraries, and most home
users pay internet service providers flat monthly fees to
connect to the internet; businesses, schools, libraries,
and other large organizations might have to internet
traffic.
Three myths about internet

91
• Someone controls the internet
– The popularity of conspiracy theories in past years has
contributed to the spread of this myth. In fact, as already
discussed, no single group or organization controls the
internet. Governments in each country have the power
to regulate the content and use of the internet within
their borders, as allowed by their laws. Making
governmental controls even harder is the “bombproof”
design of the internet itself. If a government tries to
block access to or from a specific country, for e.g. users
can establish links between the two countries through a
third country.

92
• The internet and WWW are identical
– Many people think the internet and the web are the
same thing. Even though in everyday use many people
use the terms internet and net interchangeably, they are
not the same thing. Technically, the internet is the
physical network, and the web is the collection of web
pages accessible over the internet. A majority of internet
activities today take place via web pages, but there are
internet resources other than the web. For instance,
FTP is a protocol different from the HTTP protocol used
to view web pages.

93
• The issue of internet censorship affects all countries that
have internet access. In some countries, internet content is
filtered by the government, typically to hinder the spread of
information from political opposition groups, to filter out
subjects deemed offensive, or to block information from
sites that could endanger national security. Increasingly,
some countries are also blocking information from leaving
the country, such as via blogs and personal web pages.
• Internet filtering – it is the act of blocking access to
particular web pages or type of web pages. It can be used
on home computers. It is also commonly used by employers
to keep non-work-related material off company PCs, by
some ISPs and search sites to block access to potentially
objectionable materials.
Censorship

94
• The Government of India established the Computer
Emergency Response Team ("CERT-IN") to ensure Internet
security. Many institutions, including the Ministry of Home
Affairs, courts, the intelligence services, the police and the
National Human Rights Commission, may call on it for
specialist expertise. CERT-IN's stated mission is "to
enhance the security of India's Communications and
Information Infrastructure through proactive action and
effective collaboration“.
• Currently, there is no established law stating which websites
the government censors, or when. In the past, mainly
pornographic and anti-establishment political websites have
been blocked.
Censorship

95
• Privacy relates to the internet, encompass what information
about individuals is available. As more and more transaction
and daily activities are being performed online, there is the
potential for vast amounts of private information to be
collected and distributed without individual’s knowledge or
permission.
• Cookies – many web pages use cookies – small text files
that are stored on your hard drive by a web server. The one
associated with the web page being viewed – to identify
return visitors and their preferences. For e.g., cookies can
enable a web sites to remember preferences for customized
web site content, as well as to retrieve a shopping cart
containing content on a portal page, such as session.
Web browsing privacy

96
• Browser privacy settings can be changed to specify which
type of cookies are allowed to be used, such as permitting
the use of regular cookies, but not third-party cookies or
cookies using personally identifiable information.
• Web bugs – a web bug is usually a very small image on a
web page that contains code designed to transmit data
about a web site, such as the number of visitors to the site,
the most visited pages on the site, the time of each visit,
and the web browser used.
• Spyware and adware – Spyware is the term used for any
software program that is installed without user’s knowledge
and that secretly gathers information about the user and
transmits his or her internet connection – typically to
advertisers but sometimes to criminals. Just as with cookies
and web bugs, the information gathered by the spyware
software is usually not associated with a person’s identify.
Web browsing privacy

97
• Many people mistakenly believe that the e-mail
they send and receive is private and will never be
read by anyone other than the intended recipient.
Since it is transmitted over public media, only
encrypted e-mail can be transmitted safely.
Although unlikely to happen to your personal e-
mail, nonencrypted e-mail can be intercepted and
read by someone else. Consequently, from a
privacy standpoint, a nonencrypted e-mail
message should be viewed more like a postcard
than a letter.
E-mail privacy

98
Internet governance
Internet is not governed by any particular body. It is coordinated (not
governed) by many volunteer organizations. There is no single authoritative
organization . Various volunteer organizations are responsible for different
types of activities as listed below:-
• 1) The Internet Architecture Board (IAB) is responsible for approving
standards and allocating resources.
• 2) The Internet Engineering Task Force (IETF) is responsible for discussing
and investigating the operational and technical problems of Internet.
• 3) The InterNIC is responsible for providing registration services to
Internet community.

99
Types of Transmission Media

100
Communication Media
or
Transmission Media
• Twisted Pair Cable
– It consist of two insulated copper wires, typically
about 1mm thick.
– The wires are twisted together in a helical form,
just like a DNA molecule. The purpose of twisting
the wires is to reduces from similar pairs close by.
– It is the less expensive type of networking cable
and has been in use the longest like telephone wire.
– The cables use is limited because the cables easily
pick up noise signals when line length extends
beyond 100m.

101
• Coaxial Cable (coax)
– It has better shielding that
twisted Pairs, so it can span longer
distance higher speeds.
– Two kinds of coaxial cable widely
used : 50ohm cable is commonly
used for digital transmission. 75-
ohm cable, is commonly used for
analog transmission.
– It consist of a stiff copper wire as
the core, surrounded by an
insulating material. The outer
conductor is covered in a
protective plastic shield.
Copper Core
PVC insulation
Copper mesh
Protective Plastic
Covering

102
• Fiber-Optics Cable or Optical Fiber
– It is the newest and fastest wired transmission
medium.
– It uses core glass or plastic fiber strands, each
about the thickness of human hair, to transfer
data represented by light pulses.
– The max speed is billion or even trillions of data
bits per seconds.

103
• Broadcast Radio Transmissions
– Called RF (Radio Frequency)
– Transmitter is used to send radio signals through
the air, a receiver with an antenna accepts the
data at the other end.
– Short range (Bluetooth) medium range (Wi-fi) and
long range (fixed wireless Internet Access)
Wireless Network Transmission Media or
Unguided Media

104
• Microwave Transmission
– Microwaves are high frequency, high speed
radio signals.
– They can be sent via microwave stations or
satellites.
– Can transmit large amount of data at high
speed.
– Microwaves can travel in a straight line only.

105
– Microwave stations are earth based stations placed
on tall buildings, mountains etc.
– Microwaves can also exchange data with satellites

106
• Satellite Transmission
– Space based devices placed into
orbit around the earth to
receive and transmit microwave
signals to and from earth.
– They can send and receive data
from variety of devices such as
personal satellite dishes for TV
and Internet, GPS receivers,
satellite phones
– LEO (Low Earth Orbit)-
Telephone
– MEO (Medium Earth Orbit)-
Internet and GPS

107
• Cellular Radio Transmissions
– Form of broadcast radio designed for use with
cellular telephones.
– Transmission takes place via cellular towers.
– Cellular service areas are divided into honeycomb
shaped zones called cells (2-10 miles distance and 1
tower)

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