The Internet

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The Internet
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What is Internet?

• A gigantic information storage and retrieval
  system
• Files are located in thousands of sites across
  the world

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What is Internet?

• Files contain a wide variety of digitized
  information
• text
• graphics
• audio
• video
• animation
• computer software, etc.

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What is Internet?

• The internet lets you
• look at this information
• download them to your computer
• It is a worldwide computer Network
• made up of a many smaller networks
• connected with each other
• using various communication channels
• Example- the telephone system.

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• No one owns the Internet
• No formal Management Organization
• Less vulnerable to attacks
• Very inexpensive communication media

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• To join the Internet a Network
• Has to pay a small fee
• Agree to follow certain standards
• based on TCP/IP model

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A Cheaper Communication Media
Cost is that of a local telephone call

• Each organization pays for its own
• network bills
• telephone bills
• Both independent of the Internet
• Networks forward their data to service providing
  companies (SPC)
• SPCs route and forward all traffic

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• based on the client/server technology
• A client request information from a particular
  web server
• The server sends the requested information back
  to the client
• Today's Client platforms includes
• PCs, Net PCs,
• Smart Phones, PDAs, etc

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Models of Connectivity
The Need of a common model

• How two computers using different Hardware and
  software platforms communicate each other?
• How two different Networks communicate each
  other?

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Requirements for accessing the Internet

• PC
• modem
• telephone line
• special software
• Service provider

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Modem

• Convert analogue signals into digital signals and
  vice versa
• Analogue signals
• telephone lines
• Digital signals
• computers

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Requirements for Internet Connection
Software

• Web browsers - provide you access to the
  internet and to brows web sites and web
  pages
• Examples
• Internet Explore
• Mosaic
• Netscape navigator
• Mosilla

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Requirements for Internet Connection

• Internet Service Provider (ISP)
• Organization
• has permanent Internet connections
• sells temporary Internet connections

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What can you do once you are connected?
An endless list

• download pictures to your PC
• send messages to others
• set up your own information pages
• find out details of books

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What can you do once you are connected?
An endless list

• Find out business and financial information
• See preview of movies
• Download music pieces
• Search for health related matters
• Shop from a range of suppliers
• Find details of rail timetables or airline
  reservations

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Major internet Services

• E mail
• Chatting
• Telnet
• Internet Telephony
• Virtual Private Network (VPN)
• World Wide Web (WWW)

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Major internet Services
E - mail

• A system of person - to - person messaging and
  document sharing
• connect employees and offices
• customers and suppliers, etc
• e - mail address - ggalilio_at_UnivPisa.edu.it

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E - mail
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To Access the Internet

• Specify a Uniform Rescore Locator (URL)
• Example- http//www.prenhall.com

• The URL points to an address of a specific
  resource
• on the Internet

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Domain Name System (DNS)

• A domain name
• Made up of English words and terms
• identifies a unique node on the internet
• corresponds to a unique four part numeric IP
  address

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Domain Name System (DNS)

• has sub domains separated by a period
• DNS maps domain names to their corresponding IP
  address
• memorizing numeric IP addresses is difficult

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Telnet
To do work on another
To be on one computer

• You can log on to your business computer while
  you are on traveling or at home

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Telnet

• use a computer address given
• to locate and connect the computer you want

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Telnet

• Public computers can be reached using this
• Public Computers
• that have been made accessible to the public
• ex- U.S. Library of congress

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Internet Telephony

• Two way voice transmission
• using packet switching
• Calls can be made and received
• with a desktop computer
• equipped with microphone and speakers
• or with a standard telephone or cell phone

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Internet Telephony

• users can reach
• a live customer service representative
• by clicking a link on a Web page
• No extra cost other than the cost for the
  Internet access

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Virtual Private Network (VPN)

• A secure connection
• between two points across the Internet
• enable private communication to travel
• securely over the public infrastructure

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Virtual Private Network (VPN)

• VPN services are available
• through Internet Service Providers (ISP)
• Can access remote locations
• for the cost of making a local call to an ISP

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World Wide Web

• The internet is made up of
• many servers located around the world
• and each connected to others using communication
  channels

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World Wide Web

• Servers are
• large powerful computers
• holding thousands of websites
• Many organizations and individuals
• put-up pages of information on these servers
• They have permanent IP addresses

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World Wide Web

• The WWW is a
• system for
• storing, retrieving, formatting, and displaying
  information in hypermedia form
• using client/server architecture
• A mechanism that links together information
  stored on many computers.

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World Wide Web

• A document on a computer in Sri Lanka
• can contain a reference to a stored video image
• on a computer in Switzerland

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World Wide Web

• combines multimedia
• based on standard hypertext markup language (HTML
  )

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Home Page

• To offer information through the Web
• Welcomes the user and explain the organization
• Lead the user to other pages
• All the pages together are known as the
• Website

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Home page of Unilever
http//www.unileversrilanka.com/
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Searching for Information on the Web

• Billions of Web pages
• the number double uniquely
• No comprehensive catalogue exists

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Searching for Information on the Web

• The principle methods of locating information
• Website directories
• Search engines
• Yahoo, Google , AltaVista
• Enter one or more Keywords
• and then see a list of Websites

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WWW.Orbitz.com Where you can reserve flights,
hotels, cars for rent etc.
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Intranets

• Use of Internet technology to create private
  Networks called Intranets
• Can provide access to data across the enterprise

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Intranets

• Use the existing company network infrastructure
  along with Internet connectivity standards and
  software
• Web browsers and the Web Servers are the same

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Intranets

• can create network applications that can run on
  many different kinds of computers through out the
  organization including mobile handheld computers
  and wireless computing devices

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Intranets

• Private and protracted with public visits by
  firewall
• Use HTML to program Web pages, to establish
  dynamic point and click hypertext links to other
  pages

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Intranets

• Usages
• To publish company procedures, guidelines, and
  announcements, etc
• To populate online training programmers
• To interact employees and the management

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Intranets

• internal e - mail system
• voice or video conferencing between two parties
  in the organization
• To connect remote branches of the company

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Kelaniya University Science Intranet Login page
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Extranets

• Private Intranets
• Allow limited access to people and firms outside
  the organization to Internal Intranets
• connect with
• authorizes Buyers, suppliers, business partners,
  etc

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Extranets

• Authorized buyers could
• link to a portion of a companys intranet
• to obtain information about
• the cost
• and features
• of its products

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Firewall

• Security system with specialized hardware and
  software
• placed between an organization's internal network
  and the external network
• check each data packet for characteristics
• reject unauthorized
• packets
• and attempts of access

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Web Hosting Services

• Maintains a large Web server computer or
  computers
• provides fee - paying subscribers with space to
  maintains their Websites
• create Websites for those who lacks technical
  resources

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Wireless Web

• Wireless Application Protocol (WAP) and I - Mode
• WAP lets Cell phones and other wireless devices
  with
• tiny display screens
• low bandwidth connections
• minimum memory web based information services

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Wireless Web

• WAP uses wireless Markup Language
• Uses built-in micro-browsers
• small file size
• low memory
• low bandwidth