The Internet

The Internet and Systems that Use It Internet –A group of computer networks that encircle the entire globe –Began in 1969 Protocol –Language or a set of rules for communication –All computers and devices connected to the Internet use the same protocols

Postal Service Analogy

Services that Use the Internet

The World Wide Web Developed around 1990 One of several applications that use the Internet A collection of interlinked information that is stored on computers around the world

WWW Terminology Hypertext Markup Language (HTML) –A set of codes that are included in the text describing how the text should be displayed or printed –The format used to store most files on the web World Wide Web Consortium (W3C) –Controls and monitors web communication and standards of HTML –Made up of private, educational, and governmental organizations around the world

WWW Terminology Page or web page –A text document that can contain links to other pages, web sites, or multimedia files –Written as hypertext documents using HTML –Transmitted on the Internet using HTTP protocol Client/server concept –One computer (the client) requests information from another computer (the server)

The Client/Server Concept

WWW Terminology Web browser –Client software that requests information from another program (the web server) on the WWW –First available: Mosaic (1993) –Currently most popular: Internet Explorer (65%) Netscape Navigator (23%)

WWW Terminology Web server –Computer software that retrieves information in the form of web pages, and delivers those pages to web browsers on request –The computer that is running the web server software Web site –A group of web page files and multimedia files that work together to provide information on the WWW

Using Web Browsers Browser requests a web page by sending a URL (uniform resource locator) over the Internet to the server Parts of the URL

Two Most Popular Browsers Internet Explorer –First introduced in 1995 –Download free from the Microsoft web site –Version 5.0 requires 98 MB of hard drive storage Netscape Navigator –Download free from the Netscape web site

Microsoft Internet Explorer

Netscape Navigator

Using Web Browsers AutoComplete feature Saving Web pages for later viewing Making Web pages available for off-line viewing Saving files on the Web to your PC

AutoComplete Feature

Saving Web Pages for Later Viewing

Saving Files on the Web to Your PC

A Closer Look at Web Pages Created using HTML, a form of Standard Generalized Markup Language (SGML) Hypertext document –Contains a hyperlink, or special text that is used to point to another location in a document Tag –A code in an HTML document that is used for formatting, inserting graphics, and creating hyperlinks

A Closer Look at Web Pages

Hyperlinks A tag in a hypertext document that links the location of the tag to another part of the same document or to a different document Appear as text or graphics Also called hot link or link

Finding Information on the Web Searching an individual Web site Search engines Search engine Web sites Using a browser’s search features

Searching an Individual Web Site –Static index –Site map –Keyword index –Full text index

Searching an Individual Web Site

Using a Site Map to Search a Web Site

Search Engines Software that searches for words in documents or in a database Some search only a single web site

Search Engine Web Sites Help users find information anywhere on the web Keep databases containing keywords and the URLs where the keywords are located Ways in which databases are created and maintained –A person enters keywords in a subject directory –Web crawlers, spiders, or web robots look for new information

Examples of Search Engine Web Sites Altavista Lycos Yahoo Excite HotBot Infoseek

Using a Search Engine Web Site

Using a Browser’s Search Features

Web Sites That Help Evaluate and Design Web Sites g m

Sending and Receiving Parts of Internet addresses –User name symbol –Name of the mail server that receives and then delivers the message –Example: Components of –Sending client –Sending server –Receiving server –Receiving client

Sending and Receiving

Chat Rooms Enable real time conversation among those logged on to the chat room Use an application called Internet Relay Chat (IRC)

Chat Rooms

Newsgroups Provide a place to post articles and respond to those articles Are organized around specific areas of interest Can be private or public Most popular: Usenet

Using Newsgroups Enter a URL in the address box of your web browser The browser loads the newsgroup software and passes to it the name of the newsgroup

Using Newsgroups

Introduction to the Internet Infrastructure Brief history of the Internet Network access points (NAPs)

Brief History of the Internet Late 60s-late 80s –A loosely organized group of interconnected networks, used predominantly by major academic institutions in the US for research & development 1986 –National Science Foundation formed its network called NSFnet to connect five of these academic institutions 1987 –NSF hired Merit to increase the speed of the NSFnet backbone network to accommodate growth continued

Brief History of the Internet 1990 –IBM, MCI, and Merit formed a nonprofit organization called Advanced Network and Services (ANS) to manage the NSFnet backbone –Primary users started to move from the academic to the commercial 1995 –New backbone was created and managed by MCI; NSFnet was shut down –Four Network Access Points (NAPs) were created –Merit became responsible for arbitrating the routing of all the backbones at the NAPs

Network Access Points (NAPs)

Internet Service Providers Businesses that provide individuals and companies with access to the Internet

Services Offered by an ISP Physical connection from the PC to the ISP Software to communicate over the Internet An address

Ways to Connect to an ISP

Regular Telephone Lines Most common way to connect to an ISP Require either an external or internal modem

Digital Subscriber Lines (DSL) Telephone lines that carry digital data from end to end Can be leased from the phone company for individual use Not available in all areas

Examples of DSL Technology Integrated Services Digital Network (ISDN) –A digital telephone line that carries data at about 5 times the speed of regular phone lines –Too expensive for individuals Asymmetric digital subscriber line (ADSL) –Download speed (from ISP to user) is much faster than upload speed (from user to ISP) –Within the price range of individuals

Cable Modem A technology that uses cable TV lines for data transmission requiring a modem at each end From the modem, a network cable connects to an NIC in the user’s PC

Satellite Connections Lease the service from a provider and mount a satellite dish on your premises Not a good option unless you need high speed transmission and live in a remote location that lacks alternatives

How an ISP Works