CIS 110 The World Wide Web

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CIS 110The World Wide Web
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WWW Background

• The Internet -- TCP/IP protocol
• Global network of networks. Began in 1960s as
  ARPAnet project.
• World Wide Web -- HTML protocol
• Began early 1990s.
• System of Internet servers supplying HTML
  documents (i.e. Web Pages) and supporting files.
• Hyperlinks
• Allow jumping to related documents at same or
  different server.
• Many Internet servers not part of WWW
• Web is just largest, most visible part.

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More

• Web is NOT same as Internet just one Internet
  application among many
• Email
• FTP command line vs. graphical
• Telnet seen in Linux lab
• FileSharing, etc.
• Most use Client-Server, not Peer-to-Peer
• (P2P)

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Connecting to the Internet3 Requirements

• Communications Capability
• Telephone modem, cable modem, DSL, satellite
• Speed measured in bits-per-second (bps, also
  Kbps, Mbps)
• Internet Service Provider (ISP)
• Connects to wider internet Earthlink, Comcast.
• Account usually at flat rate per month.
• Online Services use a proprietary interface
  (AOL)
• Software
• Proprietary dialer from ISP or tools (dialer,
  networking) already built into Windows.
• Web Browser, Email apps, Newsgroup readers.

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The INTER-NETwork

• A backbone is a high-capacity shared pathway for
  the network linking long distances.
• Used to be just one Internet backbone, now
  multiple private ones that are cross-linked.
• CAIDA.org

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Web Components

• Web Servers - Remote machine offering the HTML
  documents on demand.
• Web Clients - User PCs requesting documents.
• Web Browser
• Software running on the client. Retrieves
  displays HTML as Web Page. IE Netscape most
  common.
• Web Site
• Collection of linked, related Web Pages
• Home Page is the main/starting page.

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Web Addresses

• URL Uniform Resource Locator
• Use to point to a specific object
• 4 parts http//www.microsoft.com/windows98/FAQ.
  html
• Transfer protocol http
• Domain name of computer www.microsoft.com
• Pathname /windows98
• Filename /FAQ.html -- document to view
• Domain Name ex. microsoft.com
• Easy to remember.
• Related to IP Address by DNS, Domain Name Service
  
• IP Address ex. 192.168.23.114

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Domain Names and IP Addresses

• ICANN.org is the internet umbrella organization
  coordinating standards.
• The internet is actually run day-to-day by
  delegation to various companies.
• NO MASTER CENTRAL SYSTEM!!!
• Domain names are rented in effect by the
  companies.
• Domain Registrars
• Cyber-squatting Wal-Mart vs. Walmart
• Typo-squatting Drudge Report Circuit
  City
• IP addresses are issued by your ISP.

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Web Page Basics

• Web Pages
• Documents you view using a Web Browser.
• HTML - HyperText Markup Language
• Controls page appearance in browser.
• Text only. Graphics, sounds in separate files.
• HTML Tags - hidden instructions to browser
• Enclosed by to separate from displayed
  text.
• Turn formatting on/off e.g.. Bold, italics,
  color.
• Inserts objects graphics, hyperlinks
• Plug-Ins

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How the Web Works
Request URL
Send HTML

• Domain name lookup to get Server IP Address ex.
  192.168.1.3
• Send URL to Server.
• Server returns file index.html
• Browser sees Tags, asks for other files, images.
• Server sends related files.
• Document displayed.

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HTML Sample
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Transferring Files

• Can do more than just view web pages.
• Downloading
• Brings a file from the outside into your
  computer.
• Web Browser does this easily.
• Virus Danger!! Nuisance or catastrophe.
• Uploading
• Putting your files onto an outside server.
• File Transfer Protocol specialized s/w or some
  browsers

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Creating Your Own Website is Easier than You
thought

• You dont need to know HTML. Can use
• Microsoft Word Save as
• MS FrontPage
• More professional tools such as Macromedias
  Dreamweaver
• Dont need to run your own web server
• ISP gives you free space with your service.
• Web Hosting companies support smaller
  businesses who need more space, features.
• Some are free but place their own ads on your
  page.

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Interactive Web Pages

• Basic HTML is static just formatting.
• Discussion sites, weblogs (blogs), search engines
  and the catalogs and shopping carts for online
  shopping sites need more.
• Perl, PHP, ASP, Java interface with basic web
  server to do useful work and build HTML
  on-the-fly.
• Some URLs pass data to server-side programs.
  http//www.company.com/search.php?wetvac
• Web Hosts provide this extra functionality for a
  price.

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Web Searches

• Search Engines use
• A web server to interface with user
• Another program on the server to retrieve matches
  for keywords from a database built earlier by
• Web crawlers or spiders that scour the web to
  create and update an index of sites in the
  database.
• Hits and their ranking vary widely.
• Beware of Sponsored Results (paid placements)

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Search Engines 2

• Web page text can easily be scanned by web
  crawlers to index a site.
• Directly searching for images is HARD!
• Webcrawlers cant see the image.
• Some experiments with blocking based on skin-tone
  colors.
• Safe search settings

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A Search on Bear Yields This?
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Or This?
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Buzzword Intranets

• Companies use internet technologies internally
  cheap, reliable, not-proprietary.
• Internal networks hidden (and protected) from
  outside world by firewall.
• Makes it even harder to judge true size of
  internet.

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Consumer Tips

• Microsoft Internet Explorer is biggest web
  browser on the PC.
• AOL, other browsers are just re-branded Internet
  Explorer
• Browser Wars IE displaced Netscape
• Competition is heating up
• Firefox -- Opera
• Why use another? ease of use, security.