Chapter 10 Inside the Internet and the Web
Origins • 1969: ARPANET (Advanced Research Projects Agency NETwork) • Computer Scientists envisioned a need for efficient sharing of resources and ideas. • Military strategists wanted a network that could function if some connections were destroyed. • ARPANET was used by hundreds of military and university users until 1990.
The Internet: A Network of Networks The Internet is an interconnected network of thousands of networks linking academic, research, government, and commercial institutions.
Internet Services The Internet provides scientists, engineers, educators, students, business people, and others with a variety of services such as: • Electronic mail (send/receive mail messages) • Remote login(Telnet - access to other computers) • Transferring files (FTP - accessing archives of data) • Newsgroups (Usenet - on-line public discussions) • World Wide Web (a collection of multimedia documents)
Counting Connections Today, the Internet connects computers to about every country in the world. However, the Internet is: • growing too fast to measure its growth • too decentralized to quantify • a network with no hard boundaries One agency, www.internic.net, does perform some Management functions
Internet Protocols The language at the heart of the Internet is TCP/IP… • Transmission Control Protocol/Internet Protocol • Define how information can be transferred between machines and how machines on the network can be identified with unique addresses.
Internet Protocols TCP breaks messages into packets • Each packet has all the information needed to travel from network to network • Host systems called Routers determine how to route transmissions
Internet Protocols IP is the address for the packets • Each Internet host computer has a unique IP Address • Each address is comprised of four sets of numbers separated by periods, such as 22.214.171.124
Internet Access Options Direct (dedicated) Connection (T1 or T3 lines) • Computer has its own IP address and is attached to a LAN • No need to dial up • Files are stored on your computer • Response time is quick
Internet Access Options • Dialup Connections • limited connection using a modem • slowest speeds • Broadband Connections: • DSL (Digital Service Line) service is newer, faster, and cheaper than the older ISDN and allows sharing of telephone lines
Internet Access Options • Other types of Broadband Connections: • Cable Modem Connection • allow Internet connections using shared TV cables • Carry increased privacy and security risks • Satellite Connections • provides connections using DirecTV satellite dishes • Wireless Broadband: Wi-Fi • Uses short-range radio waves
Internet Access Options • Internet Service Providers (ISPs) • local ISPs provide connections through local telephone lines • national ISPs offer connections on a nationwide scale
Internet Addresses • E-mail addresses are made upof two parts separated by an at(@) sign: • User name@host name • Example: email@example.com • The host is named using DNS (domain name system), which translates IP addresses into a string of names. “Each person on the “Internet” has a unique e-mail “address” created by having a squirrel run across a computer keyboard.” Dave Barry
Internet Addresses An Internet address includes: firstname.lastname@example.org • username is the person’s “mailbox” • hostname is the name of the host computer and is followed by one or more domains separated by periods: • host.subdomain.domain • host.domain • host.subdomain.subdomain.domain
Internet Addresses Top level domains include: • .edu - educational sites • .com - commercial sites • .gov - government sites • .mil - military sites • .net - network administration sites • .org - nonprofit organizations
email@example.com Internet Addresses Examples: User President whose mail is stored on the host whitehouse in the government domain User hazel_filbert at the server for Lane County, Oregon, k-12 school district firstname.lastname@example.org
Inside the World Wide Web • WWW is a distributed browsing and searching system developed at CERN • System was designed to give Internet documents unique addresses • HTML language was created for encoding and displaying documents • Browser software was built for viewing documents from remote locations
Browsing the Web Web site Jargon: • Web pages are made up of text and images • A Web site is a collection of web pages • A Home page is the main entry to a Web site • A Web browser like Netscape Communicator or Internet Explorer allows you to explore the Web by clicking links
Browsing the Web Hyperlinks (links)are words or pictures that act as buttons, allowing you to go to another Web page Links are typically underlined or displayed in a different color
More on Browsing the Web More Web site Jargon Links allow you to locate information without knowing its exact location (it may move from time to time) Back and Forward buttons let you retrace your steps Bookmarks and Favorites can be set up to mark your favorite Web locations
Web Addresses A typical URL (Uniform Resource Locator) looks like this: http://www.prenhall.com.beekman
Path to the host http:// help/database.html www.vote-smart.org/ Web Addresses Protocol for Web pages Dissecting Web Page address: Resource Page
Searching the Web • Search engines • produce a list of pages that match a keyword • they are built around a database that catalogs Web locations based on content • Directory or Subject Tree • A hierarchical catalog of Web sites • Natural Language • Ask questions “The ability to ask the right question is more than half the battle of finding the answer.” Thomas J. Watson
Search Engines • Search engines help find information when you type a query using keywords.
Search Engines • Directory/subject tree engines offer a menu of subject choices
Search Engines • Ask questions in a Natural Language Search Engine
Portals • Portals offer quick and easy access to a variety of services such as e-mail, chat,maps, news, shopping, etc. • Examples of consumer portals include • Yahoo!, Excite, Lycos, Alta Vista, Netscape Netcenter, Snap • Specialized portals target specific industries and economic sectors