Web Browsers Networking Concepts

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Web BrowsersNetworking Concepts

• D.A. Clements

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Just a thought
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Client/Server Architecture

• Describes the relationship between two network
  computer programs
• Client a local program/computer makes a service
  request
• Server remote program/computer fulfills the
  request
• Both sides can perform relevant data processing
• As compared to older terminal/server architecture
• Common on older mainframes and mini-computers
• Terminals were dumb devices (keyboard
  monitor)
• Convenient way to link programs distributed
  across multiple locations
• Central technology of both networks and the
  Internet today
• Many different email clients and servers

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Client/Server Architecture

• Both the client and server do some work
  (processing)
• To do the complete job they each need the other
• The work each does varies with each application
• Servers tends to store data and make it
  accessible
• Database servers perform the heavy lifting
  querying, sorting
• Client is responsible for the user interface
• Making it easy for the end-user to use that data
• Client and server talk to each other using an
  agreed upon protocol for the particular
  application
• Client graphical user interfaces (GUIs)
• Much easier to understand and work with
• Make many tasks as simple as choosing from a menu
• Are less bandwidth intensive

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Client/Server Advantages

• Sometimes clients and/or servers can be built by
  different developers to meet the needs of
  end-users
• Netscape Mail, Outlook, Eudora, Outlook Express,
  Pine all different email clients that work with
  email servers
• Internet Explorer, Firefox or Netscape are web
  browser clients that can work with either IIS or
  Apache servers
• On the backend the server does the same thing
• It doesnt care what client is used, as long as
  it follows the correct protocols
• Servers from different vendors, with different
  designs can still work together to complete the
  task, as long as they both follow the correct
  protocols

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Disadvantages of Client/Server

• Interoperability issues can arise from
• Implementation differences at the client level
• Developers may interpret the standards
  differently
• Developer mistakes on either the client or the
  server
• Version problems client upgrades or updates may
  be required if the server changes
• Both the client and server must be present
• Either is useless without the other
• Network connection failures interrupt service

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Web Server Hardware vs. Software

• People often think of
• Large powerful computers are needed for servers
• Often true particularly in large organizations
• Regular PCs are only used for clients
• Even a low-end computer can be a server if they
  run the appropriate software
• Software makes the difference
• Web server application running on it, such as
• Microsofts Internet Information Services (IIS)
• Apache HTTP Server
• There are many more.
• Some devices have web server software built-in
• Provides a friendly user interface
• Used to assist in configuring and administering,
  Examples
• Printers, like many HP LaserJet printers
• Many wireless access points (A/Ps)
• Many network routers and switches

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Web Example

• Client program like Internet Explorer, Firefox
  or Netscape
• Provides the end-user interface the buttons,
  the menus, etc.
• Talks to the server using a protocol called HTTP
• Requests information by providing a URL
  (Universal Resource Locator)
• http//www.ischool.washington.edu/demo.html
• Formats the returned information properly on
  screen
• Allows the user to navigate through the page
• The server is a piece of software like IIS or
  Apache
• Provides access to information stored on the
  server in files, folders or in databases
• Make pages of information available to clients
• Each pages can include text, graphics, and links
  to other pages
• Responds to requests by sending the text,
  pictures etc
• Some pages can look different when viewed on
  different clients
• Each client has to figure out what to do with the
  information
• Final view depends somewhat on the capabilities
  of the client

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Uniform Resource Locator (URL)
http//www.cisco.com/edu/
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Web Pages

• Delivered to the client using the http (hypertext
  transport protocol)
• Content of each page is marked-up
• Using HTML (Hypertext Markup Language)
• Allows instructions to be added to the text to
  tell the browser (client) to do special things
  with parts of the text (bold, underline, change a
  color, etc)
• Browser (client) renders the page using the
  marked-up format so the page displays properly
• If the client doesnt request anything in
  particular when it goes to the site
• Most web servers display a default start page

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HTML HyperText Markup Language

• Designates the various parts of the documents,
  such as title and body
• Indicates formatting elements (like bold,
  italics, fonts, colors)
• Indicates position on the page
• Used to place links on the page that allow the
  user to navigate elsewhere
• Used to place graphics and other multimedia
  elements on the page

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A Basic Web Page
This is a web
page. This text is
displayed in bold on the
screen
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Renders as
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Web Page in Internet Explorer
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Internet Explorer

• Microsofts proprietary graphical web browser
• Part of Microsoft Windows line of operating
  systems since 1995
• Derived primarily from Spyglass Mosaic early
  web browser
• Most widely used web browser since 1999
• Version 6.0 is included in Windows XP and Windows
  Server 2003
• Through versions 6 known as "Microsoft Internet
  Explorer
• Abbreviated IE or MSIE
• Version 7 is under development beta versions
  have been released
• Name changed to "Windows Internet Explorer".
• Abbreviated WIE
• After the initial release for Windows 95
• Additional versions were developed for other
  operating systems
• Internet Explorer for Mac
• Internet Explorer for UNIX
• Only the Windows version remains in active
  development

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Mozilla Firefox

• Free, open source, cross-platform, graphical web
  browser
• Developed by the Mozilla Corporation and hundreds
  of volunteers
• One of the most downloaded free and open source
  applications
• October 19, 2005, had its 100 millionth download
• Less than 1 year (just 344 days) after the
  release of version 1.0
• Hit 200 million downloads in August 2006
• As of December 2007, estimates indicate
• Usage share is around 36 of overall browser
  usage
• Up from 12 in July 2006
• Highest usage in Germany (about 39 as of July
  2006)
• Includes
• Integrated pop-up blocker
• Tabbed browsing
• Live bookmarks
• Support for open standards
• Skinnable interface
• Extension mechanism for adding functionality

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Firefox use in Europe, July 2006

• Europe average 28
• US 34.5
• Source XiTi Monitor The Web Survey Group
  Browsers Barometer, retrieved 1/18/2007 from
  http//www.xitimonitor.com/en-us/browsers-baromete
  r/firefox-july-2007/index-1-2-3-102.html

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IE Security Note

• IE is by far one of the most hacked, attacked
  ,and compromised browsers (and applications) in
  the world
• Three major factors make IE a target for
  continued attacks
• It is integrated into the operating system,
  making a full system compromise easier for
  hackers
• By default, IE allows scripts to run that can
  easily compromise a system
• It is the most used browser in the world
• Past few years have been an ongoing battle for
  many companies trying to protect IE users from
  attacks
• February 15, 2005, Microsoft Chairman Bill Gates
  announced version 7
• In the wake of a decline in the use of IE for the
  first time
• Will provide a better security framework
• Defend users from phishing as well as deceptive
  or malicious software
• Features full user control of ActiveX
• Includes important bug fixes
• Enhancements to support the web standards
• Improvements in HTML 4.01/CSS 2
• Tabbed Browsing
• Tab preview and management
• Web feeds reader

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URL Addresses
Firefox
The same URL no matter what browser you use.
Internet Explorer
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Favorites vs. Bookmarks
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Tabbed Browsers
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Tabbed Browsers
To set multiple tabs as the default Use Tools
Options from the menu Click on Use Current Pages
button
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End papers
It has been said that man is a rational animal.
All my life I have been searching for evidence
which could support this. Bertrand Russell
(18721970)