Introduction to the Internet

What is the Internet

• The Internet is a worldwide group of connected networks that allows public access to information and services.

• 400 million users

• 200 connected countries

• 100,000 connected networks

• 12 million host computers / sites

Who owns the Internet?

• Each of the networks that make up the Internet is owned by a public or private organisation.

• No single organisation owns or controls the Internet.

History of the Internet

• Began in 1969

• Network of 4 computers – University of California (Los Angeles)– University of California (Santa Barbara)– University of Utah– Stanford Research Institute

History of Internet

• Funded by US Department of Defence– Advanced Research Projects Agency (ARPA)

• Goal 1– Develop the hardware and software needed to

create a geographically dispersed network that could function even if part of the network was disabled or destroyed

History of the Internet

• Goal 2– Create a way for scientists at different locations

to share information and collaborate on military and scientific projects.

How data is sent over the Internet“Request is sent”

• 1. Individuals connect from “home” dial in to an ISP using a modem over regular telephone lines– Once connected you can send information or

requests over the Internet. – You can request a web page by using its

Internet Address (URL)

How data is sent over the Internet“Request is sent”

• 2. Data is sent over the Internet is divided into packets. – Each packet has destination and origin

information

How data is sent over the Internet“Request is sent”

• 3. ISP uses leased lines from local telephone companies to connect to regional host computers, National ISP’s

• 4. Request is transfered to a server (a computer directly connected to the Internet that stores and serves data.– All information on the Internet originates

within servers

How data is sent over the Internet“Data is received”

• The server retrieves the requested file, divides it into packages and sends it back to the local ISP.

• The local ISP routes the packets over the Internet back to your computer

• The requested file displays on your computer screen

How the Internet Works

• Divides data into separate parts called packets, and sending them along the best route available to a destination computer.– e-mail message– file– document– request for a file

How the Internet Works

• Each packet contains– data– destination– origin– sequence information used to reassemble data

at the destination

Packet Switching

• breaking a message into individual packets

• sending the packets along the best route available

• reassembling the data

Communication Protocol

• Specifies the rules or standards used to tranmsit data

TCP/IP

The software used for packet switching on the Internet is a communication protocol named TCP/IP– Transmission Control Protocol/Internet

Protocol

Connecting to the Internet

• Connect through an Internet Service Provider– An organisation that has permanent connection

to the Internet– Provides temporary connections to others for a

fee– Internet traffic control is provided by routers,

located throughout the Internet

Internet Addresses

• Each location on the Internet has a four part numeric address called an IP (Internet Protocol) address eg 198.105.232.4– Geographical region (198)– company or organisation(105)– computer group (232)– specific computer (4)

Domain Names

• Domain names are the text version of the IP address e.g. www.microsoft.com– Web Server computer (www)– Organisation (microsoft)– Organisation type (com)

• International Web sites also include the country code e.g. ca - Canada, au - Australia

Domain Names

• Domain names are registered in the Domain Name System (DNS) and are stored in Internet computers called Domain Name Servers.

• Domain Name Servers use the Domain Name to look up the IP address

Domain Abbreviations

• .com Businesses• .edu Colleges and

Universities• .gov Government• .int International

treaty organisations

• .mil Military• .net Network and

Administrative computers

• .org Miscellaneous Organisations

The World Wide Web

• The collection of hyperlinked documents accesible on the Internet is the World Wide Web (WWW, W3 or the Web)

• Internet locations containing hyperlinked documents are called web sites

Web Pages

• A web page is a hypetext or hypermedia document residing on an Internet Computer that contains text, graphics, video or sound.

• A hypertext document contains hyperlinks to other documents

• A hypermedia document text, graphics, video or sound hyperlinks to other documents

Web Pages

• Three types of hyperlinks– Target hyperlinks

• Move from one location in a document to another location in the same document

– Relative hyperlinks• Move from one document to another document in

the same Internet computer

– Absolute hyperlinks• move to another document on a different computer

Surfing

• The ability to branch from one related to another in a nonlinear fashion

• Like using the remote control to jump from one TV channel to another

Web Pages

• Created using hypertext markup language (HTML)– set of instructions

• tags

• markups

– specify links to other documents and how the page is displayed

Web Browsers

• used to interpret the text coded with HTML tags

Web browser software

• Web Browser

• Browser

• First Browsers used text commands and displayed only text documents

• 1993 - Mosaic - displayed documents including graphics and used graphical user interface

Web Browser software

• Netscape

• Internet Explorer

• Once the connection to the Internet is established, the browser program is started.

Browser Software

• Back and Forward Buttons– Display previously viewed pages

• Stop Button– Interrupts transmission

• Refresh Button– Reloads current page

Browser Software

• Home button– Returns to designated Home Page

• Search Button– displays web search tool

• Favourites / Bookmarks– stores locations of favourite Web Site pages

Browser Software

• Print Button– print all or portion of current page

• Web address (URL) of current page

• Links– connections to other sites

• Address text box– entering a URL in address text box retrieves that

page

Home Page

• the page designated to display each time you launch your browser

Uniform Resouce LocatorURL

• Used by the Browser

• Address that points to a specific resource on the Internet

• Indicates– an Internet Site– a specific document at the site– a location within a document at a site

URL

• For WEB pages, all URL’s start with http://– hypertext transfer protocol

• the communications standard used to transfer pages on the web

– (because web pages use hypertext)

URL

• http://www.acme.com/support/techtips/VR100.html#install

• http://– Protocol; used to transfer data

• www.acme.com– domain name; identifies computer that stores

Web pages (often begins with www)

• /support/techtips– directory path; where Web page is stored

URL

• http://www.acme.com/support/techtips/VR100.html#install

• VR100.html– document name; name of Web page

• #install– anchor name; reference to a specific part of a

long document; (always preceded with #)

Browsers - Hyperlinks

• Hyperlinks to other documents– underlined text of a different color or– a graphic

• Position pointer over a hyperlink, the mouse pointer changes to a small hand with a pointing finger

Bookmarks / Favourites

• To return to a page in a future session, record location with a bookmark– title of a Web Page– URL

Searching the Web

• Search Engine– a search tool; software program that finds

• Web sites

• Web Pages

• Internet Files

– that matches one or more keywords

• Search tools do not actually search the entire Internet

Searching the Internet

• Search Tools search an index of Internet Sites and documents that is constanntly updated by the company that provides the search tool.

Search Engines

• Yahoo! www.yahoo.com

• Infoseek guide-p.infoseek.com

• Lycos www.lucos.com

• AltaVista www.altavista.digital.com

• Excite www.excite.com

• WebCrawler www.webcrawler.com

• Four11 www.Four11.com

Email

• Electronic exchange of messages from one person to another

• Messages created, sent, forwarded, stored, printed, deleted

• Must have a mailbox: - usually located on the computer that connects you to the Internet (server operated by ISP)

Internet Mailbox Address

• combination of :– username– domain name

• identifies the location of the mailbox computer

Username / Userid

• unique combination of characters that identifies you

• sometime limited to 8 characters

• must be different from other usernames on the same mailbox computer

Username

• e.g of Internet E-mail Address

gpeacock@msn.com

• username (gpeacock)

• domain name (msn.com)

Connecting to Internet & WWW

• Determine how you will obtain access to the Internet

• Obtain Necessary Equipment

• Obtain Necessary Software

• Install the Software

• Explore the Internet and WWW