UNIT - 2
WEB APPLICATION :
Networking Fundamentals
Network: A computer network
is a collection of computers and other hardware components interconnected by
communication channels (cables or satellites) that allow sharing of resources
and information.
Networks
are designed using the following architecture:
Peer
to peer (P2P): Network which all
computers have an equal status are called peer to peer networks. Generally in
such a network each terminal has an equally competent CPU.
Client-Server: Networks, in which
certain computers have special dedicated tasks, providing services to other
computers (in the network) are called client server networks. The computer(s)
which provide services are called servers and the ones that use these services
are called clients.
Types
of Network:
There
are 2 major types of network:-
1) LAN:- LAN is Local Area Network. It is used to connect computers and
devices within a small geographical area such as home, school etc.
2) WAN:- WAN is Wide Area Network. It is used to connect computers in a
broad area such as national and international boundaries.
Eg.
Internet.
Internet: Internet is a
global system of interconnected computer networks that use the standard
Internet protocol suite to serve billions of users worldwide. It is a network
of networks that consists of millions of private, public, academic, business,
and government networks.
World
Wide Web: World
Wide Web (abbreviated as WWW or W3, commonly known as the Web), is a system of
interlinked hypertext documents accessed via the Internet.
Web
Browser: A
Web Browser is software used to view Web sites and acts as an interface between
the user and the World Wide Web.
Web
Server: A
Web server is a computer that stores web sites and their related files for
viewing on the Internet.
Uses
of Network:-
1) Data Sharing: We can share data like text files, documents, audio and video
files to other users with the help of Networking.
2) Hardware Sharing: Hardware components like printers, scanners etc. can also
be shared with the help of networking.
3) Internet Access Sharing: Through networking we can access a single internet
connection on multiple computers within a network.
4) Usage of Network Based Applications: Applications
like chat applications, audio and video calling is an another advantage.
Getting
Access to the Internet:-
To
use Internet we need the following:-
1) ISP:- ISP is Internet Service Provider. It is an organization
which provides us with the access of Internet. For eg. BSNL, Airtel, MTNL etc.
2) Modem:-
The word modem is derived from its function Modulator/DEModulator. It is a
device which is used to convert digital computer signals into analog signals
and vice-versa.
Types
of Internet Connectivity
Types
of Internet Connectivity can be broadly categorized into Wired Technology and
Wireless Technology.
Wired
Technology:-
1) Dial-up:- It uses the facilities of the Public Switched Telephone Network
(PSTN) to establish a internet connection via telephone lines using a device
called MODEM. Users dial a number and get access to internet. Dial-up
connections are extremely slow.
2) DSL:-
DSL is Digital Subscriber Line provides internet connectivity by transmitting
digital data over wires of a local telephone network. It enables the use of
Telephone and Data Transmission on a single telephone line. For using DSL
Connection, we need a DSL modem and a subscription.
3) Cable Internet Access:- It is a form of broadband Internet access that uses the cable
TV infrastructure. It is provided through existing cable TV networks and it is
similar to DSL.
Wireless
Technology:-
1) 3G:- 3G, is short for 3rd Generation. It is a set of
standards used for Mobile devices and mobile telecommunication services and
networks. If the phone supports 3G, then high speed internet connectivity can
be accessed through its subscription.
High-Speed
Downlink Packet Access (HSDPA) is a 3G protocol (standard) that allows higher data
transfer speeds and capacity.
2) WiMAX:- WiMAX is Worldwide Interoperability for Microwave Access is a
wireless communications standard designed to provide mobile broadband
connectivity across cities and countries through variety of devices. It is a
long range system. It is beneficial where there is a difficulty in laying out
cables and wires.
3) Wi-Fi:- It is a popular technology used to transfer data wirelessly over
a network. Wi-Fi stands for Wireless Fidelity. The wireless network is formed
through a device called Wireless Access Point (WAP). It is beneficial as there
is no need of laying out wires for transferring data.
Data
Transfer On the Internet :-
The
data is broken up into bits of same sized pieces called packets.
A
header is added to each packet explaining where the data has come from, where
it should end up and where it fits in with the rest of the packets.
Each
packet is sent from computer to computer until it finds its destination. All
packets may not take the same route.
At
the destination, the packets are examined. If any packets are missing or
damaged, a message is sent asking for them to be resent. This continues until
all packets have been received intact.
The
packets are now reassembled into their original form. All this done in seconds!
Session 3 :
INTRODUCTION TO THE INSTANT MESSAGING
INSTANT
MESSAGING
Instant
Messaging (IM) is a form of communication over the internet that offers an
instantaneous transmission of text-based messages from sender to receiver. Most
IM software includes the option to transfer files, audio chat, video, images
etc.
Key
Features of IM are :-
1) Text message can be sent from one person to another(similar to
SMS)
2) Audio calling and conferencing
3) Video calling and conferencing
4) File Transfers
5) Message History (Save messages for future reference)
Types
of Instant Messaging Software
There
are two kinds of IM Software:-
1) Application Based:- These software are downloaded and installed on user’s computer.
Eg. Google Talk , Yahoo! Messenger , Skype , Window Live Messenger , Rediff Bol
etc.
2) Web Based:- They are accessed using browsers such as Internet Explorer
etc. Eg. MSN Web Messenger , Yahoo! Messenger for the Web , Meebo , IMO etc.
BLOG
A
blog is a discussion style site used by non-technical users for creating
personal web pages. Blog is similar to an online personal diary and similar to
use. A blog is used to convey messages, events, news, announcements etc.
Blogs
are usually managed through web browser which needs an internet connection. A
blog can also be created through Offline Blog Software and later publish the content
when the internet connection is available.
Examples
of Websites that offer blog services:-
ONLINE
TRANSACTIONS
The
transactions over the internet are called Online Transactions
Like
purchasing of goods, selling of goods, booking a ticket, payment of fees etc.
all comes under the category of Online transactions.
Examples
of Online Transaction websites:-
1) For Buying Goods :- amazon, jabong, myntra, flipkart , ebay etc.
2) For Booking of Tickets :- IRCTC , Redbus etc.
3) For Payment of School Fee :- epay.unionbankofindia.co.in/kvfee
Payment
Tools to use Online Transactions:-
For
completing an online transaction we must need:-
1) Valid Debit Card
2) Valid Credit Card
3) Net Banking Subscription
INTERNET
SECURITY
It
is a branch of computer security specifically related to the internet,
involving browser security and also network security.
Objectives
of Internet Security:-
The
main objective of internet security is to establish rules and measures to use
against attacks over the internet.
Online
Threats
The
threats / vulnerabilities that uses World Wide Web (Internet) to facilitate
crimes are called Online Threats.
Like:-
1) Phishing :- The act of acquiring personal / private and sensitive data from
personal computers for use in fraudulent activities. For eg. Mails from unknown
persons that ask for your credit / debit card details.
2) Email spoofing :- It is the creation of email messages with a forged sender
address. For eg. Sending an email with a forged email address which appears to
be original. These mails are infected mails which contain worms.
3) Chat Spoofing:- Spoofing means hoax, trick, or deceive which contains false
information. Hiding / Faking the identity of another person over the internet
is called chat spoofing.
BEST
PRACTICES FOR SECURITY OVER INTERNET
1. Use strong passwords: A combination
of alphanumeric and special characters could be used for creating a password
that is not so easy to crack or guessed by other users.
General
guidelines for strong password
a) Keep the length of the password at least 12-14 characters if
permitted.
b) Avoid keeping passwords based on repetition words, dictionary
words, usernames, pet names etc.
c) Include numbers and symbols in passwords.
d) Use Capital and lowercase letters.
e) Avoid using same password for multiple sites or purposes.
f) Avoid using something that the public or workmates know you
strongly like or dislikes.
2. Backup your data: Always keep copies of data in CD,
pendrives etc, so it could be helpful in situation when there is a loss of
data.
3. Use Encryption software: Use encrypted software
available within the operating software to protect data from unauthorized
users.
4.
Keep username and password private: Never save passwords or usernames on computers that are used in shared environments like net café.
Keep username and password private: Never save passwords or usernames on computers that are used in shared environments like net café.
5. Registering with website: Read privacy policy
whenever you register with a website, the policy will include information about
how the website use personal data.
6. Do not share personal information: Be cautious when
filling out forms on internet. Because your personal information or emails
could be used by unauthorized users to send fake or unwanted emails. So, first
research and verify if it’s a trusted website or not before providing personal
information to any website.
7. Secure transactions: It is always recommended to use only secure websites for
online shopping or transactions, because these websites store your credit card
or online banking personal information. Verify if the website uses secure
transaction, usually it is indicated through a digital certificate represented
as a golden lock in the web browser’s address bar.
8. Use Antivirus and antispyware software: These softwares
protect your computer from any changes by malwares/threats. Keep these
softwares up to date.
9. Do not immediately respond to mails from unknown
users: Some
mails, that promise you jobs or announce lottery results, may
contain virus or scripts or they can try to gather your personal
information. Never open the attachments from unknown persons.
10. Install firewalls: Firewalls keep your
system and network secure. They could be software or hardware. So, Install and
configure your firewall.
11. Regularly update your
operating system and software applications.
12. When you visit
websites, cookies are created on your system that may contain your personal or
logon details. Clear browser cookies frequently so that your logon details
could not be tracked by unauthorized users.
Computer
Accessibility :- It refers to the user friendliness of a computer system for all,
regardless of their disability. It enables a person with a disability or
impairment to use a computer. It is also known as Assistive Technology.
There
are numerous types of impairment that impact computer usage. These includes:-
1) Cognitive impairments and learning disabilities, such as
dyslexia, autism, and attention deficit-hyperactivity disorder (ADHD).
2) Visual impairment, such as low-vision, complete or partial
blindness, and color blindness.
3) Hearing impairment including deafness.
4) Motor or dexterity impairment, such as paralysis, cerebral
palsy, or carpal tunnel syndrome and repetitive strain injury.
These
accessibility options are used to customize the way your keyboard, display, or
mouse function.
Various
Accessibility Options
1) Sticky Keys:- It is an accessibility feature to help computer users with
physical disabilities. It allows the user to press and release a modifier key,
such as Ctrl, Alt, Shift etc. and have it remain active until any other key is
pressed.
2) Filter Keys:- It is an accessibility feature that tells the keyboard to
ignore repeated key strokes, making typing easier for people with hand tremors.
3) Toggle Keys:- It is an accessibility feature which is designed for people
who have vision impairment or cognitive disabilities. When toggle keys are
turned on, the computer emits a high sound when the locking keys, such as Caps
Lock, Num Lock, Scroll Lock are switched on and a low sound when they are
switched off.
4) Sound Sentry:- It is designed for the users with auditory impairments. It
generates warnings, such as blinking title bar or a flashing border, whenever
the computer generates a sound.
5) Show Sounds:- It instructs applications that convey information by sound, to
also provide information visually, through text captions or informative icons.
6) High Contrast:- It is an accessibility feature to assist people with vision
impairment. It can change the size and color of fonts and the background for
ease of viewing.
7) Cursor Options:- It is an accessibility feature that assists people with vision
impairment by changing the blink rate and width of the cursor.
8) Mouse Keys:- It is an accessibility feature that assists people who have difficulty
using a mouse. This option uses the keyboard as a pointing device instead of a
mouse.
9) Serial keys:- It is an
accessibility feature that assists people that have difficulty in using a
keyboard or a mouse or both. They can use special devices such as Sip, Puff and
Breath Switches to provide input to the computer through serial ports.
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