Web Servers, Browsers, Server Browser Interaction, Web Surfing

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Web Servers, Browsers, Server - Browser
Interaction, Web Surfing
Francis Jayakanth National Centre for Science
Information (NCSI)Indian Institute of Science
Bangalore - 560 012 (E-Mail franc_at_ncsi.iisc.erne
t.in)
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Web Servers, Browsers, Server - Browser
Interaction, Web Surfing

• Web Information Architecture
• Client-Server Computing
• What is a World Wide Web Server?
• Web Server Software

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Web Servers, Browsers, Server - Browser
Interaction, Web Surfing

• Web Server Hardware
• Web Server Administration
• Web Server - Web Browser Interaction
• Web Clients or Web Browsers
• Surfing the Web

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Web Information Architecture

• Web servers and browsers
• Web servers store variety of web compatible
  documents and provide access to these on the
  Internet or an intranet
• PCs, RISC-based workstations/servers
• These documents are accessed using Web browsers
  like Netscape and IE
• Palm tops, Laptops, PCs, workstations, etc.

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Web Information Architecture

• Web sites and URL
• One or more web servers identified with a unique
  web site address on the Internet (e.g.
  www.iisc.ernet.in)
• Documents available on a Web site are uniquely
  identified using the URL scheme access
  protocol//host.domain port/path/file
  name(Ex. http//www.ncsi.iisc.ernet.in/ncsi/data
  base.html)

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Web Information Architecture...

• Anatomy of a web site
• Hardware, software (OS, web server, CGI,
  database, indexing and search, etc.)
• Dedicated Internet/intranet connectivity
• Information content Documents stored in variety
  of formats (HTML, SGML,PDF, databases, images,
  audio, video, etc.)

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Web Information Architecture...

• Anatomy of a web site
• HTML pages integrate access to this information
• Organized in a hierarchical manner
• Home page (root page) provides links to second
  level HTML pages which in turn link to third
  level HTML pages, and so on
• These pages may contain images and provide access
  to databases through search forms, PDF files,
  audio and video, etc. or link to documents on
  other servers

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Web Information Architecture...
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Web Information Architecture...
The World Wide Web is non-linear. There is no
top, there is no bottom. Non-linear means you do
not have to follow a hierarchical path to
information resources.
You can jump from one link (resource) toanother
You can go directly to a resource if you know the
Uniform Resource Locator (URL) (its address)
You can even jump to specific parts of a document.
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Client-Server Computing

• The Client computer is connected via a network to
  the server computer. The server stores and
  manages the data the client answers, updates,
  processes and formats the data the network
  provides conduit between the two.
• The Client-Server computing provides the sharing
  of work between the server computer which acts as
  backend and the client computer which acts as
  front end and allows each to perform the function
  it does best the network provides the conduit
  between the two.
• Client computer could be PCs (DOS, Windows), Mac,
  workstations, mini or mainframe computer.
• Servers usually operate on multi-user OS machines
  such as UNIX or Windows NT

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What Is a World Wide Web Server?

• A World Wide Web Server is comprised of
• Web server software running on a multi-user
  computer that is directly connected to the
  Internet
• Web servers respond to requests from Web clients
  called Web browsers (Netscape or Internet
  Explorer).
• Web Servers use Hypertext Transfer Protocol
  (HTTP) to respond to requests from Web clients
• Because Web Servers communicate with Web browsers
  using HTTP protocol they are also referred to as
  HTTP servers.

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Web Server Software

• Obtaining and installing server software
• Your computers operating system determines the
  type of Web server software you can use.
• Both free commercial server software programs
  are available.
• After you acquire the appropriate server software
  you will need to uncompress it.
• Refer to Readme or Install.txt file included with
  server software for specific installation
  instructions
• Next, you will need to configure the software

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Web Server Software

• Server software for Unix OS
• The NCSA Server maintained by the National Centre
  for Supercomputing Applications at the University
  of Illinois at Urbana-Champaign.
• Documentation is available at http//hoohoo.ncsa.
  uiuc.edu/docs/
• Operating System support Most Unix variants
  (Source 893k)
• Availability Free
• http//hoohoo.ncsa.uiuc.edu/docs/setup/Download.ht
  ml

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Web Server Software

• Server software for Unix OS
• Apache, a variation of NCSA that has grown into
  the most popular Web server today.
• Documentation and downloads available from
  www.apache.org.
• Apache also comes bundled with Linux OS.
• Operating System support Unix, Windows NT,
  Windows 95, OS/2, Amiga OS (Source 1242k,
  Binary(1.3.0) 1533k)
• Availability Free
• http// www.apache.org.

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Web Server Software

• Server software for Windows
• 1. Omnihttpd
• Availability Free
• http//www.omnicron.ab.ca/files/ohttpd101.exe
• 2. Xitami
• Avilability Free
• http//www.imatix.com/html/xitami/index2.htm
• 3. Sambar Server
• Availability Free
• http//www.sambar.com/location.htm

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Web Server Hardware

• The type of computer system required to setup a
  Web server depends on the services provided on
  the server, volume of usage and the network
  bandwidth
• If other Internet services like E-mail, FTP are
  to be provided from the same system, then the
  server should be more powerful with adequate hard
  disc storage space
• Another influencing factor is the volume and type
  of content to be served - images, audio and video
  contents require more storage space and I/O
  throughput

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Web Server Hardware...

• A Pentium II or III class computer with 64-128 MB
  RAM, and 4 GB or more hard disc storage provides
  satisfactory performance.
• Higher-end servers can be set up using RISC based
  workstations/servers
• Web servers also need backup devices like DAT or
  cartridge tape drive to take backup of important
  files.
• An Uninterruptible Power Supply (UPS) to the
  server is a must.

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Web Server Performance Factor

• Some key factors that affect the performance of
  Web servers are
• LAN WAN bandwidth
• Web page composition
• Disc fragmentation
• Processor speed of the server
• Network Interface card
• Disc controllers
• Fault tolerance
• Power problem
• Application design

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Web Server Administration

• Most of the Web server software keeps track of
  the Web client software accessing the server, the
  files on the server that are being accessed and
  the error messages that the users encounter while
  accessing the server. These information are are
  written into log files. For example, the log
  files maintained by NCSA httpd server are
• access_log
• Requests made to the server are recorded in this
  file
• agent_log
• Clients accessing the server are recorded in this
  file
• error_log
• Errors encountered by the server are recorded in
  this file
• referer_log
• The name of the document that was sent in
  response to a request are recorded in this file

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Web Browsers or Web Clients

• A Web browser is a software application that is
  used to to view Web pages. Most of the browsers
  can also be used to
• Send and receive e-mails
• Read messages from newsgroups
• Web browsers read the html text and convert it
  into a page
• Currently there are two popular GUI based Web
  browsers, the Netscape Communicator and the
  Microsoft Internet Explorer
• Lynx is the text-based Web browser

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Web Browsers or Web Clients

• Web browsers are fully customizable. You have
  option of changing the size of the text and style
  of the font that is displayed.
• You also have the option of changing the home
  or startup page that appears when the browser
  is started

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Web Server and Browser Interaction

• A Web browser acts as an interface between the
  user and Web server
• The browser carries out the following tasks on
  behalf of the user
• Contacts a Web server
• Sends a request for information
• Receives the information and
• Displays the information on the local system

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Web Server and Browser Interaction
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Web Server and Browser Interaction

• If you click the Open button on your browser and
  type any URL (eg http//www.ncsi.iisc.ernet.in/
  ), the browser generates a GET request, connects
  to the server at a designated IP address and
  waits for a response.The server returns a
  response and closes the connection. This is the
  basic browser and server interaction.

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Customizing Your Browser

• Customizing the Toolbars
• Changing What's Displayed on Toolbar Buttons
• Hiding a Toolbar
• Moving a Toolbar or Toolbar Button
• Adding and Deleting Toolbar Buttons
• Changing Fonts, Colors or Backgrounds
• Specifying the Components That Appear at Startup
• Specifying the Starting Page

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Handling Different File Types

• Browsers can handle many types of files. However,
  for some files, such as movies, browser launches
  a "helper" application that can handle the file,
  or it saves the file for you to view later.
• The settings in the Applications preferences
  panel tell the browser which helper applications
  to use on your computer.

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Improving Speed, Efficiency, and Privacy

• Automatic Loading
• When you bring a web page to your screen, the
  browser automatically loads (starts up) several
  features that help interpret web pages. These
  features can make web pages more lively, but they
  take time to load.
• To turn off automatic loading
• Deselect one or more of the following

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Improving Speed, Efficiency, and Privacy

• Automatically load images. Automatically displays
  images in a web page when you view the page. If
  unselected, images are replaced by small icons,
  and you click the Images button in the toolbar to
  view the images.
• Enable Java. Allows Java applets (small programs
  that add functionality to pages) to run
  automatically.
• Enable JavaScript. Allows JavaScript (commands
  that add functionality to pages) to run
  automatically.
• Enable style sheets. Displays pages formatted by
  style sheets as the author intended. If
  unselected, author's formats aren't included.

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Changing Cache Settings

• Your computer stores copies of frequently
  accessed pages in the memory cache or disk cache.
  This way, the computer doesn't have to retrieve
  the page from the network each time you view it.
• Important A larger memory cache allows more data
  to be quickly retrieved. But unless you have a
  lot of extra memory on your computer, 1024K is
  large enough.

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Getting the Latest Software Automatically

• Smart Update allows software to be automatically
  and securely installed on your machine in one
  step.

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Setting Proxy Values

• Many organizations block access from the Internet
  to their networks. This prevents outside parties
  from gaining access to sensitive information. The
  protection is called a firewall.
• If your organization has a firewall, the browser
  may need to go through a proxy server before
  connecting you to the Internet. The proxy server
  prevents outsiders from breaking into your
  organization's private network.

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Surfing the Web

• Finding Information on the Web
• Viewing a Page
• Moving to Another Page
• Retracing Your Steps
• Retracing Your Steps in Detail The History List
• Viewing a Page's Information
• Viewing a Page's Source Code
• Searching Within a Page

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Moving to Another Page

• You move to a new page by typing its URL--its
  location (address) on the Web.
• To move by clicking a link
• 1.Move the pointer until it changes to a pointing
  finger. This happens whenever the pointer is over
  a link.
• 2.Click the link once. While the network locates
  the page the link points to, status messages
  appear at the bottom of the window.
• If you change your mind and don't want to view a
  page, click Stop

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Retracing Your Steps

• To view the previous page
• Click Back (or Forward).
• To view a page from the current session
• Open the Go menu and choose the page you want to
  return to.
• To view a page whose URL you recently typed in
  the Location field
• (Windows only) Click the down-pointing arrow at
  the right end of the Location field, and choose
  from the pop-up menu.

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Retracing Your Steps in Detail The History List

• Browsers maintain history list of pages you have
  viewed recently, as determined by your
  preferences.
• To view a page, double-click its line in the
  list.
• Sorting the History List
• Click one of the categories (Title, Location, and
  so forth). Click again to reverse the order
  (ascending or descending by date, number, or
  alphabetical order).

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Viewing a Pages Information

• Viewing a Page's Information
• You can view information about the files that
  compose a page
• Viewing a Page's Source Code
• To view the HTML and other code that generates a
  web page

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Bookmarking Your Favorite Web Sites

• Creating a Bookmark
• To bookmark a web page
• 1.Go to the web page you want to bookmark.
• 2.Click Bookmarks.
• 3.Choose Add Bookmark.
• The name of the currently displayed page is added
  as the last item in the Bookmark menu.
• To revisit a bookmarked web page
• 1.Click Bookmarks.
• 2.Choose a bookmarked page.

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Creating an Internet Shortcut

• An Internet shortcut lets you jump to a web page
  from your desktop or from folders on your
  computer. There are three ways to create Internet
  shortcuts.
• To create a shortcut from a link
• Drag a link in a web page to the desktop.
• To create a shortcut for the current web page
• Drag the bookmark icon to the desktop.
• To create a shortcut using the bookmark list
• 1.Click Bookmarks and choose Edit Bookmarks.
• 2.Drag the bookmark you want to the desktop.
• You can drag a shortcut into any folder on your
  computer.

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Copying, Saving, and Printing Pages

• Copying Part of a Page
• To copy some text from a page
• 1.Select the text.
• 2.Choose Copy from the Edit menu.
• You can paste the text into other files.
• To copy a link (URL) from a page
• 1.Right-click the link or image to display a
  pop-up menu.
• 2.Choose Copy Link Location or Copy Image
  Location. If an image is also a link, you are
  offered both options.

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Saving a Page

• To save an entire page
• Choose Save As from the File menu.
• When you view a page containing frames and a
  frame is currently selected, the File menu's Save
  Frame As option is offered in addition to Save
  As. This lets you save only the page within the
  selected frame.
• Saving a file onto your hard disk lets you view
  the page (or its HTML code) when you're not
  connected to the Internet.

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Saving a Page

• To save an image from a page
• 1.Right-click the image to display a pop-up menu.
  
• 2.Choose Save Image As.
• To save a page without displaying it (useful for
  retrieving a nonformatted page, like a data file,
  that's not intended for viewing)
• 1.Right-click the page's link.
• 2.Choose Save Link As.

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Saving a Page

• Important Some links automatically download and
  save files to disk after you click them. The URLs
  for these links often begin with "ftp" or end
  with a file-type suffix such as "au" or "mpeg".
  These links might transmit software, sound, or
  movie files, and can launch helper applications
  that support the files.

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Printing a Page

• To print the current page
• Click Print.
• On Windows, you can choose Print Preview from the
  File menu to see how the printed page will look.
• Note When you view a page containing frames, the
  File menu contains Print Frame in place of Print.
• Important Browsers format content according to
  the size of the printed page, not the size of the
  onscreen window. Text is word-wrapped and
  graphics are repositioned to accommodate paper
  size.

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