1. # 1# 1 CS 105 Fall 2006 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?

2. # 2# 2 CS 105 Fall 2006 Connecting to the Internet ISP (Internet Service Provider)—connects to the Internet, and the user pays the hook-up fee and use charges. Examples: AOL, MSN, UIUC  Modem—Uses a phone line to reach a server  ________________ — needs a cable modem (not really a modem!) Only if you have a T1 line do you have a direct connection to the Internet

3. # 3# 3 CS 105 Fall 2006 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 __________________, for redundancy Wireless

4. # 4# 4 CS 105 Fall 2006 Wi-Max Coming soon! 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.

5. # 5# 5 CS 105 Fall 2006 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. E-mail protocols: –SMTP - Simple Mail Transfer Protocol –POP - Post Office Protocol File transfer protocol: FTP It is all based on…

6. # 6# 6 CS 105 Fall 2006 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. Involves packets. packets Terminology

7. # 7# 7 CS 105 Fall 2006 Terminology HTTP -- HyperText Transfer Protocol The protocol used for a web document (HTML). Example: http://www.uiuc.eduhttp://www.uiuc.edu HTTPS: –A HTTP protocol that provides for more secure web communications by including encryption methods.

8. # 8# 8 CS 105 Fall 2006 VOIP -- Internet TelephonyInternet 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

9. # 9# 9 CS 105 Fall 2006 You send a message to someone. First it goes to a server Sending email Electronic messages are sent to your account and stored on a

10. # 10 CS 105 Fall 2006 Email software is later used to download messages from the __________ that is storing the message. You receive email from the server, where it has been stored for you

11. # 11 CS 105 Fall 2006 Peer-to-Peer Systems like KaZaa Files held on individual machines rather than centralized server from: http://www.pcpitstop.com/spycheck/p2p.asp

12. # 12 CS 105 Fall 2006 Client/________ Relationship What is a server?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

13. # 13 CS 105 Fall 2006 Internet Addressing - IP Addresses Computer ports, called servers, connected to the Internet have unique addresses. 222.230.112.7 222.230.112.5 222.230.112.6 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

14. # 14 CS 105 Fall 2006 Internet Addressing - Domain names These 4-part numbers are converted into easy-to-remember domain names. amazon uiuc.edu, google.com, eBay.com google

15. # 15 CS 105 Fall 2006 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

16. # 16 CS 105 Fall 2006 The URL http://www.cs.uiuc.edu/~roberta/ http://....... specifies Hypertext Transfer Protocol, / www.cs.uiuc.edu......... Identifies location of web server ~ means bypass intermediate directories and go straight to the directory named roberta (~ is called a tilde) index.html........ is the name of the home page and will appear whether or not you type index.html!

17. # 17 CS 105 Fall 2006 Internet Addressing - URL Example https://netfiles.uiuc.edu/moor12/www/cluster/news.html Secure Protocol Top Level Domain Student or Employee HTML Documen t Folder

18. # 18 CS 105 Fall 2006 Spam, Phishing – Where does this link take you?

19. # 19 CS 105 Fall 2006 Internet Addressing - Top level domains You can find out who owns a domain name. –www.networksolutions.com/cgi- bin/whois/whoiswww.networksolutions.com/cgi- bin/whois/whois whitehouse.gov uiuc.edu google.com

20. # 20 CS 105 Fall 2006 Top Level Domains.comCommercial businesses.orgNon-profit organizations.netNetwork services.govGovernment agencies.eduEducational institutions.milMilitary.intInternational.nomFor individual users.webWeb-based businesses.AERO,.BIZ,.COOP,.INFO,.MUSEUM,.NAME, and.PRO

21. # 21 CS 105 Fall 2006 Common Country Domains.auAustralia.fiFinland.cn China.ukUnited Kingdom.usUnited States.il Israel.ch Switzerland.mxMexico and more

22. # 22 CS 105 Fall 2006 Sample Email Address username @ hostname.com Your userID Name of your ISP’s host computer “at” Jin45@uiuc.edu

23. # 23 CS 105 Fall 2006 Using ph to find a person’s email address http://www.uiuc.edu/ricker/PH

24. # 24 CS 105 Fall 2006 To summarize: 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?