CBSE :: CLASS XII : INFORMATICS PRACTICES (065)

UNIT 3 : INTRODUCTION TO COMPUTER NETWORKS

MARKS : 10 Marks

Syllabus

Introduction to networks, Types of network: LAN, MAN, WAN.

Network Devices: modem, hub, switch, repeater, router, gateway

Network Topologies: Star, Bus, Tree, Mesh.

Introduction to Internet, URL, WWW, and its applications- Web, email, Chat, VoIP.

Website: Introduction, difference between a website and webpage, static vs dynamic web page, web server and hosting of a website.

Web Browsers: Introduction, commonly used browsers, browser settings, add-ons and plug-ins, cookies.

History of Networks & Internet

• They created an early form of the Internet called ARPANET in 1969. (Advanced research projects administration network)
• In 1971 electronic mail, or e-mail, was invented as a way to send a message from one computer to another.
• By the mid-1970s many groups of computers were connected in networks. ... In 1989 hypertext was invented.
• Hypertext is a link between different parts of an electronic document or between different documents. Hypertext became the basis of the World Wide Web, or “the Web,” which was created in the early 1990s.

UCLA - Univ. of Calif. at Los Angeles UCSB - Univ. of Calif. at Santa Barbara UTAH - Utah University SRI - Stanford Research Institute

UCSB Network

UTAH Network

UCLA Network

SRI Network

ARPANET

E-MAIL

E-mail stands for electronic mail. It is the most widely used tool to send messages electronically (ie through computers) on a network.

E-mail messages are generally sent from and received by mail servers – computers that are dedicated to processing and directing e-mail.

E-mail address syntax: username@hostname

Example of E-mail : rajeshbabu123@gmail.com

Here Username is “rajeshbabu123”, Hostname is “gmail.com”

E-MAIL

Advantages :

Low cost

Speed

Waste Reduction

Ease of Use

Record Maintenance

Patience

E-MAIL

Disadvantages/Limitations:

Hardware requirement

Impermanent

A hasty medium

Hard to convey emotions

Difference between CC (carbon copy) and BCC (blind carbon copy):

They forward a copy of the message to everyone you’ve listed.

But in BCC the recipients do not get to know each other

SPAM & JUNK MAIL

Spam is defined as irrelevant or inappropriate messages sent on the Internet to a large number of people.

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Junk mail is the unwanted or unsolicited advertising or promotional material received through mail or email.

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These two terms typically are used interchangeably.

CHAT

Online textual talk is called chatting

You type a message on your screen, which is immediately received by the recipient; then the recipient can type a message in response to your message, which is received by you instantly.

Ex: Messenger, Whats app, Google Chat, etc

VoIP

VoIP (Voice Over Internet Protocol) : is a technology that makes audio and video calls possible from any internet connected device having a microphone and speakers. Applications like WhatsApp, Telegram, FaceBook Messenger, Skype, Google Duo, Meet, Zoom, etc use VoIP to make calls over Internet.

On the internet, Communication is the responsibility of Internet Protocol (IP). VoIP allows for the transmission of voice along with other data being communicated over IP.

VoIP takes audio/video input in analog type and converts them into digital information so that it can be transferred over internet along with other data on IP.

VoIP

Adantages:

1. It does not cost extra as long as you have a device with an Internet connection and are using it for personal use. Ofcourse there are paid versions available for professional requirements.
2. Easily available. Many VoIP based software such as Skype, are easily downloadable.

Disadvantages:

1. VoIP is possible if both the caller and the receiver have the right software and hardware to speak to one another.
2. There is no guarantee of call’s audio and video quality when using the internet.
3. It uses internet protocol’s packets so if packets get dropped along the way then voice quality drops.
4. Even with its high quality, it cannot match up the voice quality of a normal telephone line.
5. It may not work for emergency service numbers like police or fire services regular numbers.