introduction to the internet. what is the internet the internet is a worldwide group of connected...
TRANSCRIPT
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
• 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
• 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