Information and Communication Technology FundamentalsCredits Hours: 2+1

Instructor: Ayesha Bint SaleemInstructor: Ayesha Bint Saleem

NETWORKS - III

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Presentation Credits

• “Introduction to Computer” by Peter

Norton

• “Using Information Technology” by

Williams and Sawyer

• “Introduction to Information Technology”

by V. Rajaraman

The Internet’s History• 1969 – ARPANET

• Developed by the Department of Defense• Connected universities and defense bases

• 1973 – ARPANET connects to Europe

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ARPANET 1973

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The Internet’s History• Mid-1980s – NSFNet

• Network between supercomputers• Internet was the link to ARPANET• No commercial traffic allowed

• 1990s• ARPANET shut down• NSFNet abandoned• Commercial networks take over

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Today and the Future• Thousands of networks• Hundreds of millions of users• Huge co-operative community with no

central ownership• Anybody can access it

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THE INTERNET’S MAJOR SERVICES

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1. E-mail

• Stands for electronic mail

• One of the “killer application” for the

internet

• Use E-mail client

• E.g. outlook express

• Web based email service

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E-mail (contd)

• E-mail addresses

• ayesha.saleem@niit.edu.pk

• Unique id

• Email server

• Or email service provide e.g hotmail.com

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E-mail (contd)

• Mail Server

• When you send an email, message is stored on

email server, until the recipient can retrieve it

• Many mail server use Post Office Protocol (POP)

• Also called POP servers

• Internet Message Access Protocol (IMAP)

• Used by local clients to retrieve email from

email servers

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E-mail (contd)

• Mail Server

• Simple Mail Transfer Protocol (SMTP)

• Used by mail servers to send/receive messages

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E-mail (contd)

• E-mail features

• Audio, Video, Images can be sent as

attachment

• Reply, Reply All, Forward, Delete, CC, BCC

• Listserv

• Lists of e-mail addresses

• Each address gets the e-mail

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Spam: Unwanted Junk E-Mail

•Delete without opening the message

•Never reply to a spam message!

2. Information Browsing

• “To retrieve and display specified

information stored in one or more

computers connected to a computer

network”

• Implies interactivity

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Menu Based Browsing

• Earliest browsers were menu based

• Gopher

• Menu is presented

• User selects a menu item

• Gopher software will search table to find out where the

required information is stored

• May be on another computer

• Retrieve information and display

• Look up process hidden from user

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Hypertext Based Browsing

• A system in which documents scattered across

many Internet sites are directly linked, so that a

word, phrase or an image in one document

becomes a connection to a document in a

different place

• User clicks a word/image

• Document is retrieved

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Hypertext Based Browsing (contd)• Hypertext systems provide an easy way to

manage large collections of data scattered

world wide

• Documents can be interconnected

• Facilitates non-linear reading

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World Wide Web

• Billions of documents, stored in different places,

linked together in some manner

• “Web” of interconnected information

• Collection of documents and links spread all

over globe

• “World wide web”

• Developed in 1993 by Tim-Berners Lee

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How the web works?

• HyperText Transfer Protocol (HTTP)

• Special protocol used by web to supports hypertext

documents

• HyperText Markup Language (HTML)

• Hypertext documents are encoded in HTML

• A notation to mark keywords in documents

• Allows author to embed hypertext links

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How the web works? (contd)

• Uniform Resource Locator (URL)

• Method of naming documents or places on

the Websites

• String of characters that identifies

• the type of document,

• the computer the document is on,

• the directories and subdirectories the document

is in, and

• the name of the document.

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How the web works? (contd)

• Uniform Resource Locator (URL) (contd)

http://www.nps.gov/abli/index.htm

• Protocol : http

• Domain name: www.nps.gov

• Directory name: abli

• File name: index.htm

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How the web works? (contd)

• Hypertext Browser

• Marc Anderson developed Mosaic web browser

• Some popular browsers today are

• Internet Explorer

• Firefox

• Netscape communicator (successor to Mosaic)

• URLs can be typed in a browser

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How the web works? (contd)

• Web pages and Websites

• A hypertext document is called a web page

• Collection of related web pages is a website

• A Web page is a document on the World Wide Web

on a Website that can include text, pictures, sound,

and video

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How the web works? (contd)

• Helper Applications

• Many websites feature multimedia content

• Browsers alone cannot display every type of

content

• Multimedia files requires special

applications in order to be played in real

time

• Also called plug-in applications

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How the web works? (contd)

• Helper Applications (contd)

• Plug-ins support several types of content

including audio and video streaming

• Content is sent in a continuous stream (still

in packets) from web server to browser

• Plug-in receives first portion and buffers it

• First portion is played while next portion is

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Streaming Audio

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Some Common Plug-ins

Searching the World Wide Web

• The Web is unorganized

• Directories

• Categorize the Internet

• Search engines

• Find sites by keyword

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• Resource Directories

• Directory separates subjects in categories

• Typically employ human experts

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Searching the World Wide Web

Resource Directory

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Searching the World Wide Web• Search Engine

• Search using keywords

• E.g. Google.com

• Offer advanced options as well

• Do not use humans to index documents

• Automated programs called “web crawlers”

• browse world wide web in a systematic manner

• Pick keywords

• Create index

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Searching the World Wide Web

• Meta Search Engine

• Uses multiple search engines simultaneously

to lookup your keyword

• Searhenginewatch.com

• News about different search engines

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Other Internet Features• File Transfer Protocol (FTP)

• Allows you to access any computer connected to the

internet and download files

• FTP Site is a collection of files housed on an FTP

Server

ftp://ftp.xcollege/admission-rules

• Remote server, ftp.xcollege, will prompt for a login id

and password

• Public FTP archives accept “anonymous” as user id

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• Telnet

• Logging on to a remote computer and using

its facilities

• telnet: <domain name of computer> or IP

address

• Login ID and Password

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Other Internet Features

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Other Internet Features• Internet Relay Chat (IRC)

• Real time communication system• Multi-users with many channels (rooms)• Channels are dedicated to a topic• All users can read the comments

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Other Internet Features• Instant messaging (IM)

• Private, real-time communication• Message sent only to listed users• Buddy lists contain IM names

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Other Internet Services• Peer-to-peer (P2P) services

• User computers are connected together• No centralized organization• Users can communicate directly• Users can share files

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Other Internet Services

• Internet Radio

• Audio from radio station is stored in high

speed disk memory of server

• Person wishing to listen to broadcast logs on

to the server and listens to it by downloading

it using internet

• Intermittent reception due to packet switching

• Start with delay

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Other Internet Services

• Internet Telephony

• Normal telephony is circuit switched

• Expensive

• Talk over packets

• Low cost

• Quality may not be the best

• Voice over IP (VoIP)

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Other Internet Services

• Video Conferencing

• Voice + Video over Internet

• Different standards exist