Lecture 03 Going Online

Topics Basics Connecting to the Internet World Wide Web Internet Applications Internet Ethics

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Basics

Internet: worldwide collection of interconnected networks; Computers are no longer lonely ARPANET (1969): network for scientists that evolved into the Internet Internet backbone: major communications lines and nodes to which thousands of hosts are connected

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Basics

No one group controls the Internet, but some organizations coordinate Internet activitiesThe Internet Society to assure the open development, evolution, and use of the InternetICANN (Internet Corporation for Assigned Names and Numbers): responsible for coordinating the assignment and allocation of domain names and internet addressesW3C (World Wide Web Consortium): create and maintain technical specification to keep pace with changing technologies used on the Internet

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Connecting to the Internet

Bandwidth: amount of information that can be sent over the channel, in bps (bits per second)Broadband – high bandwidthNarrowband – low bandwidth

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Connecting to the Internet

Narrowband Dialup service

Phone line Modem 56 Kbps

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Connecting to the Internet

Broadband Cable

TV cableLAN PC card Cable modem1 M~10 Mbps

DSL (Digital Subscriber Line)Phone lineLAN PC card ADSL modemUpstream rate: 128Kbps~1.5MbpsDownstream rate: 1.5M~9Mbps

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Connecting to the Internet

Broadband (cont)Satellite

Satellite discSatellite modemLAN PC cardUpstream rate:56Kbps~1.5MbpsDownstream rate: 400Kbps~1.5MbpsLatency – time lag in communication

Wireless AP (Access Points) Wireless LAN PC card Wi-Fi (Wireless Fidelity) standard

Wireless-B (IEEE 802.11b)/11Mbps/300ftWireless-A (IEEE 802.11b)/54Mbps/50ftWireless-G (IEEE 802.11g)/54Mbps/Far better than A

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Connecting to the Internet

ISP (Internet service provider) Communication software (Dialup/ DSL) Hinet/ Seednet

Information service gateway Communication software (link to the information network of AOL) user ID and password AOL (America OnLine)/ MSN

Direct LAN connection T-1 line (1.544Mbps) T-3 line (44.736Mbps)

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Connecting to the InternetProtocol TCP/IP (Transmission Control Protocol/Internet Protocol)

Protocol: set of rules for how computers communicate, defining message format and interaction patterns Packet: the part of a message that contains the data and the address the message is being sent to Packet switching

TCP dividing files into packets IP routing each packet to destination

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Connecting to the Internet

IP (Internet Protocol) addressIdentify each device attached to the Internet by numbersFour numbers, each 0~255, separated by periods, e.g., 206.28.104.10

Fixed vs. Dynamic IP address Domain names

Identify each device attached to the Internet by symbols, e.g., ailab2.et.ntust.edu.twtop-level domains: denote affiliation

.com/.eduDNS (Domain name system)

Translate domain names to IP addresses

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Connecting to the Internet

URL (Uniform Resource Locator)Identify each resource on the Internet, e.g., ftp://ailab2.et.ntust.edu.tw/www/InfoTech/Lecture01.pptFour parts

access method: ftpDomain name: ailab2.et.ntust.edu.twPath name: www/InfoTechResouce: Lecture01.ppt

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Connecting to the Internet

Client program runs on user’s computer

Internet browser/ FTPPro Server program – runs on server computer

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Connecting to the Internet

More devices to connect to the Internet

televisions/ Freezer video game consoles PDA/ cellular phones Internet appliances

A specific device to go online at anytime, any place

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World Wide Web

WWW, the Web (World Wide Web)Website

Web serversContaining webpages and server programsHome page – first page you see at a site

WebpageA document containing multimedia data and hyperlinksHyperlinks – allow user to click on an icon and be taken to other resources on the InternetDocument structure is specified by HTML/ XML/…

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World Wide Web

WWW, the Web (World Wide Web)

BrowsersA client program which interprets a webpage and interacts with the Web serverIE/ Netscape/ KKman/ Mozilla Firefox

HTTP (Hypertext Transfer Protocol)

A protocol for client and server programs to communicate © 2005 Prentice-Hall, Inc. Slide 17

World Wide Web

HTML (HyperText Markup Language)

A language to format a webpage using paired tags, e.g., <i> </i>; <a> </a>Define how each multimedia component in a webpage is displayed

XML (eXtensible Markup Language)

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World Wide Web

Browser Plug-insSoftware modules that are integrated into a browser to add flexibilityAnimation/ multimedia displays

Applets or ActiveX controlsStreaming audio and video

Media is presented continuously instead of being downloaded

Java RTE/ Flash player/ Window Media Player/ RealJukebox/ QuickTime/iPIX Movies/ Acrobat Reader/ Liquid Player

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World Wide Web

Common operations of Browser Back: go to previous page Forward: go to next page Stop: ends transmission Refresh: reload Web page Bookmarks (Favorites): have browser remember favorite sites Location bar: where user enters URL

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World Wide Web

Finding information on the Web Browsing: just looking around portals

Portal: a site that provides a number of services Classified Index databaseYahoo/ Yam/ Excite..

Searching: trying to find specific information by using search engines

Search Engine: a program that goes to the Internet or within a Website to search for webpages users needGoogle/ Yahoo/ Excite/ MSN/Hotbot/ Ask Jeeves/ Infoseek/ AltaVista/ Metacrawler/

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World Wide Web

Tips for searching the Net Read the rules for each search engine Try multiple search engines Follow hyperlinks Choose search terms carefully Be persistent Use FAQ (Frequently Asked Questions)

lists answers to questions asked often at a particular site

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Internet Applications

Resource retrieval WWW

Web server user-friendly multimedia documents hyperlinks interactive frames Integration of Internet applications, e.g., FTP, email, ..

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Internet Applications

Resource retrieval (cont)FTP (File Transfer Protocol)

FTP serverEasily download/upload filesAnonymous FTP sites

JukeboxHelp a client program to gather mp3 and other audio files from Internet music resources

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Internet Applications

Communication E-mail

e-mail server file attachments

Newsgroups Mailing lists or listservs

push technology – information is delivered automatically from the server to client programs

ChatInstant messaging (Whiteboarding)

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Internet Ethics

Netiquette Using all capital letters is considered SHOUTING Never send unsolicited e-mail (spam) Consider your audience when forwarding Internet content

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Internet Ethics

Netiquette (cont) Never reveal others’ personal information Be patient with people who are justgetting online (newbies) Don’t comment on others’ spelling,grammar, or punctuation

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Internet Ethics

Netiquette (cont) Keep private communications private Consider e-mail attachment sizebefore sending to someone (using dialup) Confirm virus warnings before forwarding Use an anti-virus program

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Internet Ethics

Shady side of the Internet Hackers and crackers Hate mongers Pornography

Filtering programs

Spam Gambling

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