Lecture 14 Internet and World Wide Web

1. Lecture 14 Internet and World Wide Web

2. Internet (Inter Network) Network Comprising of Numerous Worldwide Networks Largest Network in the World Connects Commercial, Academic and Government Networks Cannot Estimate the Number of Computers Comprising the Internet Attempt to “Map” the Internet Would Be a Futile Endeavor Attempts Have Been Made

3. Internet (ca. 1999)

4. Internet (ca. 2008)

5. ARPANET • Predecessor of the Internet • Created in 1969 (mid 1960s) • Advanced Research Projects Agency • Designed to Ensure the Government's Ability to Continue Communicating in the Event of a Nuclear Attack • Initially Connected Four Supercomputers • Evolved into Today’s Internet

6. Internet Community • Users • People Who Use the Internet • Internet Service Providers (ISPs) • Provide Users Access to the Internet Resources Typically for a Fee • Includes Most Communication and Media Companies

7. Internet Content Anyone Can Add Content to the Internet No One Person or Organization Owns the Internet Application Service Providers and Web Services Provide Resources

8. Protocols • Protocol • Set of Rules for a Particular Situation • Communications Protocol • Rules that Determine How Devices on a Network Communicate • Computer Devices Cannot Transfer Data without Applying the Same Protocol

9. TCP/IP Protocol • Widely Used Communications Protocol • Built into Most Operating Systems • Used to Identify Computers and Devices on Networks • Consists of Two Protocols • Transmission Control Protocols (TCP) • Responsible for Delivery of Data • Internet Protocols (IP) • Addressing and Routing Information

10. Transmission Control Protocol • Rules for Transmitting and Receiving Data Packets Over the Internet • TCP Sets the Size of the Data Packets • TCP on Server Computer Breaks Web Page Data into Data Packets, Numbers the Packets, and Sends Data Packet • TCP on Client Computer Reassembles the Data Packets in the Correct Order

11. Internet Protocol • Rules Governing the Method by which Data Packets Are Transmitted • Most Important Function Is Uniquely Identifying Each Computer (Host) • A Host Is Identified by a 32-bit IP Address • Every Computer Connected to the Internet Must Have an Unique IP Address

12. IP Address IP Addresses Are Expressed as Four Decimal Numbers e.g., 131.171.8.112 Each IP Address Has Two Parts: Identifier of a Particular Network on the Internet Identifier of the Particular Device within that Network

13. Transferring Data Example • Data Packet Is Sent from Transmitting Computer to a Gateway Computer • Gateway Computer Reads IP Address, Forwards to Another Gateway Node • Known as Routers • When Destination Gateway Recognizes the IP Address, Data Packet Is Forwarded to the Device within the Network Domain

14. Internet Routers

15. Internet Related Protocols • For Displaying Web Pages • HTTP: Hypertext Transfer Protocol • HTTPS: HTTP Secure • For Transferring Files Over the Internet • FTP: File Transfer Protocol • For Delivering E-mail Over the Internet • SMTP: Simple Mail Transfer Protocol • POP3: Post Office Protocol 3 • IMAP: Internet Message Access Protocol

16. The World Wide Web • Collection of Web Pages on the Internet • Proposed by Tim Berners-Lee (1989) • Originally Text-based Content • Graphical Content with Mosaic (1993) • Based Upon Hypertext Markup Language • HTML and HTTP

17. The Web Convenient and User-friendly Users Do Not Need to Be Experts The Fastest Growing Component of the Internet Internet Protocols Are Web Accessible Java, JavaScript, Visual Basic, XML The WWW Is a Dynamic Environment Stretching the Functions of the Internet

18. Search Engines • Popular Function on the World Wide Web • Specialized Applications which Provide Three Main Applications or Functions • A Spider Application Searches and Identifies Internet Web Pages • A Catalog Application Creates an Index of the Spider's Search • A User Interface Compares a Request with the Catalog Providing Results

19. Electronic Mail Transfer of ASCII Text Messages between Computers or Devices Messages Are Received on an Internet Server and Not to User’s Computer Most E-mail Applications Use SMTP POP3 Is Designed as a Store and Forward Application IMAP Is Designed as a Remote File Server

20. Other Web-Based Services • Instant Messaging (IM) and Chat (IRC) • Message Boards • Voice Over Internet Protocol (VOIP) • Web Conferences and Webinars • Online Shopping • Online Banking and Investing • Online Entertainment • Online News

21. Web 2.0 • Enhanced Version of the WWW • Social Networking • Twitter • Blogs • RSS (Really Simple Syndication) • Podcasts • Wikis

22. Internet and WWW Issues • Censorship • Countries Blocking Internet Content • Hinders Spread of Information from Political Opposition • Internet Filtering • Using Software or Browser Options to Block Access to Particular Web Pages or Types of Web Pages

23. Internet and WWW Issues • Spyware • Software that Transmits Data Secretly without Users’ Knowledge • Adware • Onscreen Advertising Software • Often Included in Free Programs • Does Not Gather Information • Is Installed without User’s Consent

24. Internet and WWW Issues • E-mail Privacy • Employers’ Access to E-mail Messages • Only Encrypted E-mail Can Be Transmitted Privately • Web Browsing Privacy • Information About an Individual’s Web Browsing, How Used, and by Whom • Often Retained in Cookies

25. Internet and WWW Issues • Social Networking • Users Should Be Careful Not to Reveal too Much About Themselves • Sites Monitored by Employers • Carefully Check What Is Posted • Remove Anything that Might Be Potentially Embarrassing

26. Myths About the Internet Myth 1 The Internet is Free Myth 2 Someone Controls the Internet Myth 3 The Internet and the World Wide Web Are One and the Same

27. Lecture 14 Internet and World Wide Web