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CHAPTER 4 THE INTERNET AND INTRANETS What is the Internet? A collection of interconnected networks, all freely exchanging information The Largest computer network in the world (a network of networks)

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chapter 4

CHAPTER 4

THE INTERNETAND INTRANETS

what is the internet
What is the Internet?
  • A collection of interconnected networks, all freely exchanging information
  • The Largest computer network in the world (a network of networks)
  • Exchanges information seamlessly by using the same open, non-proprietary standards and protocols, within interconnected networks
  • Forms a massive electronic communications network

Marina G. Erechtchoukova

the evolution of the internet
The Evolution of the Internet

Marina G. Erechtchoukova

the infrastructure of the internet
The Infrastructure of the Internet
  • Commercial communications carriers provide the physical network backbone of the Internet
  • Internet Service Providers:
    • Backbone providers
    • Access providers
  • Reciprocal agreement

Marina G. Erechtchoukova

the operation of the internet
The Operation of the Internet
  • Internet is packet-switched network
  • Client-Server architecture
  • Internet Protocol
  • Internet Model

Marina G. Erechtchoukova

internet model
Internet Model
  • Interface layerdefines physical medium and frame for flow and error control
  • Internet network layer defines the path to intended receiver in the network. Uses Internet Protocol (IP)
  • Internet transport layer provides point-to-point reliable transmission of data. Uses TCP and UDP.
  • Internet application layer supports network application

Marina G. Erechtchoukova

osi model vs internet model
OSI Model vs. Internet Model

Marina G. Erechtchoukova

internet application layer
Internet Application Layer
  • File Transfer Protocol
  • Telnet
  • Simple Mail Transfer Protocol
  • Simple Network Management Protocol
  • HyperText Transfer Protocol
  • Domain Name System

Marina G. Erechtchoukova

addresses on the internet
Addresses on the Internet
  • IP address uniquely identifies each computer in the network
  • Example: 130.63.160.120
    • The necessity to keep a master table with IP addresses on each router
    • Hard to remember for people
  • Uniform Resource Locator
  • Domain name system (DNS) - derives the names of the computers

Marina G. Erechtchoukova

domain name system dns
Domain name system (DNS)
  • Domain – a group of networks
  • Domains are organized hierarchically
  • DNS is based on hierarchical database:
    • Variable-depth hierarchy
    • Distributed database
  • Examples:www.atkinson.yorku.ca

www.yorku.ca

Marina G. Erechtchoukova

accessing the internet
Accessing the Internet
  • Connect via LAN Server
    • Communications stack
  • Connect via Serial Line Internet Protocol/Point-to-point Protocol (SLIP/PPP)
  • Connect via an Online Service

Marina G. Erechtchoukova

internet services
Internet Services
  • Communications services
  • Information retrieval services
    • World Wide Web

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communications services provided by the internet
Communications Services Provided by the Internet
  • E-mail
  • Instant messaging
  • Internet telephony:
    • Voice-over-IP
  • Video conferencing
  • Content streaming

Marina G. Erechtchoukova

the world wide web
The World Wide Web
  • The Internet functions as the transport mechanism
  • The World Wide Web - a system with universally accepted standards for storing, retrieving, formatting, and displaying information
  • Web Servers – support WWW application, are scattered all over the world

Marina G. Erechtchoukova

web site
Web site
  • Web Site
  • Home Page - first, introductory page in a web site
  • Webmaster - the person in charge of a Web site
  • Uniform Resource Locator (URL)

Marina G. Erechtchoukova

browser
Browser
  • software application that is used to access and navigate the Web
    • Netscape Communicator
      • a multipurpose suite that handles news, e-mail, audio- and video conferencing, and more
    • Microsoft Internet Explorer
      • Internet Explorer’s tight integration with Windows offers users the advantage of “one-stop computing”

Marina G. Erechtchoukova

search engines
Search Engines
  • Programs that return a list of Web sites or pages that match some user-selected criteria
  • Ways to select pages for inclusion in the database:
      • Web Crawlers
      • TITLE HTML element
      • Registration – sponsored link

Marina G. Erechtchoukova

web authoring
Web Authoring
  • Standard HTML is the common denominator
  • Enhancements to HTML
      • Dynamic HTML (DHTML) (slide # 6, Introduction to HTML)
      • Extensible markup language (XML)
      • Voice markup language (VoxML)
      • Virtual reality modeling language (VRML)
  • HTML editors, generators, publishers
  • Java

Marina G. Erechtchoukova

internet privacy
Internet Privacy
  • Web sites collect information about visitors:
    • Registration
    • Clickstream data
  • Cookie is a mechanism that supports restoring client states
    • small data file placed on users’ hard drives when they first visit a site

Marina G. Erechtchoukova

internet security
Internet Security
  • Encryption – the process of converting a message into a secrete code
    • Plain text – original message
    • Ciphertext – encrypted text
  • Decryption - the process of converting an encrypted message into regular text
  • Digital signature is used to verify the identity of a message sender

Marina G. Erechtchoukova

intranets
Intranets
  • A private network that uses Internet software and TCP/IP protocols
  • Process business data and information efficiently:
    • Data and information search
    • Urgent information delivery
    • Information distribution

Marina G. Erechtchoukova

intranet operation
Intranet operation
  • Intranet documents – HTML pages
  • HTTP – used to transmit documents
  • Browsers – allow to view Intranet documents
  • Intranet vs. traditionalnetworks:
    • HTTP and HTML platform independent
    • A single input point – a browser

Marina G. Erechtchoukova

extranet
Extranet
  • A network that links business partners to one another over the Internet by providing access to certain areas of each other’s corporate intranets
  • Extranet infrastructure:
    • Virtual private network
    • Firewall

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virtual private network
Virtual Private Network
  • A secure connection between two points across the Internet
  • Provides the means for conducting private communications over the public Internet.
  • VPN vs. privately owned network

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tunneling
Tunneling
  • The process by which VPN transfers information
  • Messages include data along with private protocol information
  • Does not substitute encryption

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firewalls
Firewalls
  • A system designed to prevent unauthorized access to or from a private network.
  • Firewalls can be implemented in:
    • Hardware
    • Software
    • a combination of both.

Marina G. Erechtchoukova