 2002 Prentice Hall Chapter 10 Inside the Internet and the Web

 2002 Prentice Hall 2 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.

 2002 Prentice Hall 3 The Internet is an interconnected network of thousands of networks linking academic, research, government, and commercial institutions. The Internet: A Network of Networks

 2002 Prentice Hall 4 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) Internet Services

 2002 Prentice Hall 5 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, does perform some Management functions

 2002 Prentice Hall 6 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

 2002 Prentice Hall 7 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

 2002 Prentice Hall 8 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

 2002 Prentice Hall 9 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

 2002 Prentice Hall 10 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

 2002 Prentice Hall 11 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

 2002 Prentice Hall 12 Internet Access Options Internet Service Providers (ISPs)  local ISPs provide connections through local telephone lines  national ISPs offer connections on a nationwide scale

 2002 Prentice Hall 13 Internet Addresses addresses are made up of two parts separated by an sign:  User name  Example: 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 “address” created by having a squirrel run across a computer keyboard.” Dave Barry

 2002 Prentice Hall 14 Internet Addresses An Internet address includes:  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

 2002 Prentice Hall 15 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

 2002 Prentice Hall 16 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

 2002 Prentice Hall 17 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 Inside the World Wide Web

 2002 Prentice Hall 18 Browsing the Web 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 Web site Jargon:

 2002 Prentice Hall 19 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

 2002 Prentice Hall 20 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

 2002 Prentice Hall 21 Web Addresses A typical URL (Uniform Resource Locator) looks like this:

 2002 Prentice Hall 22 Web Addresses Protocol for Web pages Dissecting Web Page address: Path to the host Resource Page help/database.html

 2002 Prentice Hall 23 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

 2002 Prentice Hall 24 Search Engines Search engines help find information when you type a query using keywords.

 2002 Prentice Hall 25 Search Engines Directory/subject tree engines offer a menu of subject choices

 2002 Prentice Hall 26 Search Engines Ask questions in a Natural Language Search Engine

 2002 Prentice Hall 27 Portals Portals offer quick and easy access to a variety of services such as , 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