Learning Objectives • Define how the Internet works • Describe the services associated with the Internet • Describe the World Wide Web • Define the terms intranet and extranet and discuss how organizations use them • Identify who is using the Web to conduct business
Internet Networks Linked networks that work much the same way -- they pass data around in packets, each of which carries the addresses of its sender and receiver. The Internet (Figure 7.1) The Internet transmits data from one computer (called a host) to another.
Use and Functioning of the Internet • Interconnected networks • Global though US is the largest user • Internet Protocol (IP) • Research for a faster Internet • Internet2 (I2) • Next Generation Internet (NGI) • Corporate efforts
How the Internet Works • Hosts with Uniform Resource Locator (URL) • Routers forward packets to other networks • Internet Protocol Stack (TCP/IP) • Internet Protocol (IP) • Transport Control Protocol (TCP) • Backbones • One of the Internet’s high-speed, long distance communications links.
How the Internet Works • Uniform Resource Locator (URL) • http://www.whitehouse.gov World Wide Web Domain category Hypertext transfer protocol Host Network Name
The Internet is Based on the Client-Server Model • In client/server computing, processes are divided between the client and the server. This relationship is based on a series of requests and responses. • Client: Requests services or information from another computer (the server computer). • Server: Responds to the client's request by sending the results of the request back to the client computer.
CLIENT SERVER REQUEST Client Program RESPONSE Server Program Send Request Process Request Read Results Send Back Results The Client-Server Model This diagram illustrates the relationship between client and server computers. The client requests information; the server processes the request and sends a response back to the client.
Examples of Client Server Transactions • FTP (file transfer protocol) - An FTP client program contacts an FTP server and requests the transfer of a file; the FTP server responds by transferring the file to the client. • WWW (World Wide Web) - In this case the client program is a browser. A browser requests the contents of a web page and displays the results on the user's computer. • E-MAIL - A mail client program enables the user to interact with a server in order to access, read and send electronic mail messages.
To: Destination: From: Instruction Fields: Data Packets: The Internet “Letter”
What is a Packet? A packet is a single unit, or "package", of data that is sent across a network. Data is broken into packets before it is sent across the Internet. Types of data that are sent across the Internet using packets include: • E-mail messages • Files, via File Transfer Protocol (FTP) • Web pages, via the World Wide Web (WWW)
To: Destination: From: Instruction Fields: Data Parts of the Packet The HEADER of a packet contains both the originating and destination IP (Internet Protocol) address. The header also contains coding to handle transmission errors and keep packets flowing. Routers use the data in the header to get the packet to the correct address and to reassemble it at the destination. The DATA portion of the packet contains the e-mail text, the web page information, or the contents of the file.
Transmission Control Protocol/Internet Protocol (TCP/IP ) • TCP/IP is a collection of protocols, or rules, that govern the way data travels from one machine to another across networks. • The Internet is based on TCP/IP. TCP/IP
Internet Protocol • Determines how much data can fit into a single packet • Breaks the data into packets. • Places header information into the packet, enabling the packet to be forwarded from router to router until it reaches the final destination..
Hi Bob! Hi Bob! Packet Switching Example
Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Packet Switching Example
18.104.22.168 Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Packet Switching Example Router Router Router
Hi Bob! Hi Bob! Packet Switching Example
Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Hi Bob! Packet Switching Example
U.S. Top-Level Domain Affiliations Affiliation ID Affiliation arts cultural and entertainment activities com business organizations edu educational sites firm businesses and firms gov government sites info information service providers mil military sites nom individuals net networking organizations org organizations rec recreational activities store businesses offering goods for purchase web entities related to World Wide Web activities net networking organizations
Accessing the Internet • Fig 7.2
Internet Service Providers (ISPs) • Provide Internet access to account holders • Monthly fee varies • Some are free
Internet Service Providers Internet Service Provider Web Address AT&T WorldNet Service www.att.com Digex, Inc. www.digex.net GTE Internetworking www.gte.net IBM Internet Connection www.ibm.net MCI Internet www.mci2000.com NetCom On-Line Communication Services www.netcom.com PSINet, Inc. www.psinet.com Sprint Internet Services www.sprint.net Uunet Technologies, Inc. www.us.uu.net
Internet Services • E-mail (Electronic mail) • Can include images, attachments, or HTML • Routed by gateways and routers • Telnet: remote login • FTP: file transfer
Internet Services • Chat rooms: allow interactive conversations • Instant Messaging: online, real-time communication over the Internet • Videoconferencing • Internet phone
Internet Services • Content streaming: transfers multimedia files continuously so users can view them in real-time • Music, radio & video • 3-D Internet sites
The WWW is Just a Part of the Internet • The World Wide Web, also referred to as the WWW and "the Web," is the universe of information available via hypertext transfer protocol (HTTP). • The World Wide Web and HTTP: • allow you to create "links" from one piece of information to another; • can incorporate references to sounds, graphics, and movies, etc.; • "understand" other Internet protocols, such as ftp, gopher, and telnet.
WWW Pages use Hyperlinks • The Web presents information as a series of "documents," often referred to as web pages, that are prepared using the Hypertext Markup Language (HTML). • Using HTML, the document's author can specially code sections of the document to "point" to other information resources. These specially coded sections are referred to as hypertext links. Users viewing the webpage can select the hypertext link and retrieve or connect to the information resource that the link points to. Library Catalog (telnet) Webpage Software Repository (ftp) link link gopher site w/ images & sounds link
The World Wide Web • A collection of tens of thousands of independently-owned computers that work together as one in an Internet service. • Uses a menu-based approach and hyperlink technology in a client/server topology. Hypermedia Tools that connect the data on Web pages, allowing users to access topics in whatever order they wish. Home Page The cover page for a Web site that has graphics, titles, and black and blue text.
Uniform Resource Locators (URL) Identify Sources of Data on The Internet • A URL identifies a particular Internet resource. e.g. a Web page, a gopher server, a library catalog, an image, or a text file. • URLs represent a standardized addressing scheme for Internet resources. The basic structure of a URL is hierarchical moving from left to right: protocol://server-name.domain-name.top-level domain: port/directory/filename Examples: • http://www.healthyway.com:8080/exercise/mtbike.html • gopher://gopher.state.edu/ • ftp://ftp.company.com/
Several Interesting Web Sites Library of Congress http://lcweb.loc.gov PointCast http://www.pointcast.com In-Box Direct http://www.netscape.com Online Career Center http://occ.com New York Times http://www.nytimes.com Project Gutenberg http://www.gutenberg.org Sportsline USA http://www.sportsline.com White House http://www.whitehouse.gov MIT CS Lab http://www.lcs.mit.edu The Wall Street Journal http://www.wsj.com
Web Terminology • Web Server: Computer that stores web pages. • Web Browser • Software that creates a unique hypermedia-based menu on your computer screen and provides a graphical interface to the Web. • Web Page • A screen of information sent to a requesting user and presented through a browser. • Applet • A small program embedded in Web pages • Search engines • Programs to find web pages of interest.
Internet Services • Shopping on the Web • Bots: web search tools • Web Auctions • Office on the web
Webcasting • aka Push Technology • Consolidates information according to a user’s profile & displays in the browser
Intranets and Extranets • Intranet • An internal corporate network built using Internet and World Wide Web standards and products that allows employees of an organization to gain access to corporate information. • Extranet • A network based on Web technologies that links selected resources of the intranet of a company with its customers, suppliers, or other business partners. 22