# 1# 1 cs 105 fall 2006 internet and web concepts what is a url? the internet and the world wide web...
DESCRIPTION
# 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 WirelessTRANSCRIPT
CS 105 Fall 2006 # 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?
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Connecting to the InternetISP (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
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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
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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.
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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…
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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.
Terminology
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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.
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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
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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
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• 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
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Peer-to-Peer • Systems like
KaZaa
• Files held on individual machines rather than centralized server
from: http://www.pcpitstop.com/spycheck/p2p.asp
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Client/________ Relationship
What is a server? • Some computers on
the network offer services that others can access.– ftp server -- email– Yahoo, Google -- – Library
cataloguesYour query goes to the
serverServer sends
back information
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Internet Addressing -IP Addresses
• Computer ports, called servers, connected to the Internet have unique addresses.
222.230.112.7
222.230.112.5
222.230.112.6IP 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
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Internet Addressing -Domain names
• These 4-part numbers are converted into easy-to-remember domain names.
amazon
uiuc.edu, google.com, eBay.com
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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 generalcs.uiuc.edu
educational siteUniversity of Illinois @ Urbana-ChampaignComputer Science Department
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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!
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Internet Addressing -URL Example
https://netfiles.uiuc.edu/moor12/www/cluster/news.html
SecureProtocol
Top Level Domain
Student or Employee
HTMLDocument
Folder
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Spam, Phishing – Where does this link take you?
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Internet Addressing -Top level domains
• You can find out who owns a domain name.–www.networksolutions.com/cgi-bin/whois/whois
whitehouse.gov
uiuc.edu
google.com
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Top Level Domains.com Commercial businesses.org Non-profit organizations.net Network services.gov Government agencies.edu Educational institutions.mil Military .int International.nom For individual users.web Web-based businesses
.AERO, .BIZ, .COOP, .INFO, .MUSEUM, .NAME, and .PRO
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Common Country Domains• .au Australia• .fi Finland• .cn China• .uk United Kingdom• .us United States• .il Israel• .ch Switzerland• .mx Mexico
and more
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Sample Email Address
username @ hostname.com
Your userID Name of your ISP’shost computer
“at”
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Using ph to find a person’s email address
• http://www.uiuc.edu/ricker/PH
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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?