Internet and Web Concepts

1. Internet and Web Concepts • What is a URL? • The Internet and the World Wide Web (subset) • What is a browser? • HTTP is? • cs.uiuc.edu means… • What do we mean by client-server? CS 105 Fall 2007

2. What we learn in the next part of CS105 How does the Internet work? Interacting with a database on the Web Spreadsheet basics CS 105 Fall 2007

3. Connecting to the Internet ISP (Internet Service Provider)—connects to the Internet, and the user pays the hook-up fee and use charges. Examples: Insight, Charter, UIUC • Modem—Uses a phone line to reach a server • Broadband — needs a cable modem (not really a modem!) Only if you have a T1 line do you have a direct connection to the Internet CS 105 Fall 2007

4. Other means of connecting • DSL (Digital Subscriber Line) — uses a DSL transceiver. You use your regular phone line, too. • Wireless at home needs only one hub and then no wires • Wireless in a community involves a web of routers for redundancy CS 105 Fall 2007

5. Wi-Max • Hitting Chicago First! Sprint is bringing it to Chicago as a test market. • A technology that will enable delivery of “last mile” wireless broadband access as an alternative to cable and DSL. • WiMAX can offer wireless connectivity at up to 30 miles from an antenna! Wi-Fi only works a short distance from the source. CS 105 Fall 2007

6. Programs communicate, not computers A program on one computer uses protocol software to contact a program on another computer– a protocol is an agreed format that computers on the Internet use to communicate. • Email protocols: • SMTP - Simple Mail Transfer Protocol • File transfer protocol: FTP • WiMax will have a secure protocol—everything will be encrypted. • Internet communication is all based on… CS 105 Fall 2007

7. Terminology TCP/IP Transmission Control Protocol/ Internet Protocol TCP/IP is an agreed format that computers on the Internet use to communicate. Any computer that understands TCP/IP can connect to the Internet. Involvespackets. CS 105 Fall 2007

8. Terminology • HTTP -- HyperText Transfer Protocol The protocol used for a web document (HTML). Example: http://www.uiuc.edu • HTTPS: • A HTTP protocol that provides for more secure web communications by including encryption methods. CS 105 Fall 2007

9. VOIP -- Internet Telephony • Make your phone calls over the Internet! Voice over Internet Protocol; using packet based networks instead of the standard telephones to send voice data CS 105 Fall 2007

10. Email software is later used to download messages from the server that is storing the message. You receive email from the server, where it has been stored for you CS 105 Fall 2007

11. Peer-to-Peer • Systems like KaZaa • Files held on individual machines rather than centralized server from: http://www.pcpitstop.com/spycheck/p2p.asp CS 105 Fall 2007

12. Client/ Server Relationship What is a server? • Some computers on the network offer services that others can access. • ftp server -- email • Yahoo, Google -- • Library catalogues Your query goes to the server Server sends back information CS 105 Fall 2007

13. Internet Addressing -IP Addresses • Computer ports, called servers, connected to the Internet have unique addresses. IP number is a 32-bit address in four parts, of 8 bits each, and therefore, in 8 bits you can only represent the numbers 0 to 255 (256 possible numbers). Thus this address is not possible: 299.230.112.5 222.230.112.5 222.230.112.6 222.230.112.7 CS 105 Fall 2007

14. Internet Addressing -Domain names • These 4-part numbers are converted into easy-to-remember domain names. uiuc.edu, google.com, eBay.com google amazon CS 105 Fall 2007

15. Domain Naming System • provides mnemonic help in identifying sites • organizes the names of computers, subnetworks, and larger networks • reading left-to-right, information becomes more general cs.uiuc.edu educational site University of Illinois @ Urbana-Champaign Computer Science Department CS 105 Fall 2007

16. https://netfiles.uiuc.edu/georgia/www/ https:// ....... specifies secure Protocol, netfiles.uiuc.edu/......... Identifies location of web server (Hidden from the user—used to be noted by a tilde (~), computers find exact user of many thousands) index.htmlis the name of the home page and will appear whether or not you type index.html! The URL CS 105 Fall 2007

17. Internet Addressing -URL Example Secure Protocol https://netfiles.uiuc.edu/moor12/www/news.html Folder HTML Document Top Level Domain Student or Employee CS 105 Fall 2007

18. Spam, Phishing – Where does this link take you? CS 105 Fall 2007

19. Internet Addressing -Top level domains • You can find out who owns a domain name. • www.networksolutions.com/cgi-bin/whois/whois uiuc.edu google.com whitehouse.gov CS 105 Fall 2007

20. Top Level Domains .com Commercial businesses .org Non-profit organizations .net Network services .gov Government agencies .edu Educational institutions .mil Military .int International .name For individual users .web Web-based businesses http://en.wikipedia.org/wiki/Generic_top-level_domain CS 105 Fall 2007

21. Common Country Domains • .au Australia • .fi Finland • .cn China • .uk United Kingdom • .us United States • .il Israel • .ch Switzerland • .mx Mexico and more CS 105 Fall 2007

22. Sample Email Address Jin45@uiuc.edu username@hostname.com “at” Name of your ISP’s host computer Your userID CS 105 Fall 2007

23. Using ph to find a person’s email address • http://www.uiuc.edu/ricker/PH CS 105 Fall 2007

24. Do you know how to explain these? • What is a URL? • The Internet and the World Wide Web (subset) • What is a browser? • HTTP is? • cs.uiuc.edu means… • What do we mean by client-server? • Your moment of Zen—the wired world • http://www.opte.org/maps/static/1069646562.LGL.2D.700x700.png CS 105 Fall 2007