Chapter 8: Web Server Hardware and Software

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Chapter 8Web Server Hardware and Software
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Web Server Basics

• The main job of a Web server computer is to
  respond to requests from Web client computers
• Three main elements of a Web server
• Hardware
• Operating system software
• Web server software

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Types of Web Sites

• Development sites
• Used to evaluate different Web designs
• Intranets
• Corporate networks that house internal memos,
  corporate policy handbooks, and a variety of
  other corporate documents
• Extranets
• Intranets that allow authorized parties outside
  the company to access information stored in the
  system

• Transaction-processing sites
• Commerce sites that must be available 24 hours a
  day, seven days a week
• Content-delivery sites
• Deliver content such as news, histories,
  summaries, and other digital information

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Web Clients and Web Servers

• Client/server architectures
• Client computers typically request services
• A server processes the clients requests
• Web software
• Lets different types of computers running
  different operating systems communicate

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Client Server Architecture and Software
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Dynamic Content

• Dynamic content is nonstatic information
  constructed in response to a Web clients request
• Dynamic page
• Web page whose content is shaped by a program in
  response to user requests
• Static page
• An unchanging page retrieved from disk

• Server-side scripting
• Programs running on a Web server create Web pages
  before sending them back to the requesting Web
  clients
• Dynamic page-generation technologies include
• Active Server Pages (ASP)
• JavaServer Pages (JSP)
• PHP Hypertext Preprocessor (PHP)

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Various Meanings of Server

• Server
• Computer used to provide files or make programs
  available to other computers
• Server software
• Used by a server computer to make files and
  programs available to other computers
• Database server
• Server computer on which database management
  software runs

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Server Architecture

• Two-tier architecture
• A web server responds to requests for web pages
  and a database server provides backend data
  storage
• Multi-tier architecture
• A web server is linked to a middle-tier layer
  that typically includes a series of application
  servers that perform specific tasks, as well as
  to a backend layer of existing corporate systems

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Two-Tier Client/Server Architecture

• Two-tier client/server architecture has only one
  client and one server
• Request message
• Message that a Web client sends to request a file
  or files from a Web server
• Typical request message contains
• Request line
• Optional request headers
• Optional entity body

• Request line
• Contains a command, the name of the target
  resource, and the protocol name and version
  number
• Request headers
• Can contain information about types of files that
  the client will accept in response to a request
• Entity body
• Used to pass bulk information to the server

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Three-Tier and N-Tier Client/Server Architectures
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Web Application Servers

• Software programs that provide the specific
  business functionality required of a web site.
  Include
• Catalog display
• Transaction processing
• Audio/video server
• Auction server
• B2B server

APACHE has 62 of the market of Web server
software Exercise For more information, go to
www.apache.org
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Right-sizing Your Hardware Platform The Supply
Side

• Scalability the ability of a site to increase in
  size as demand warrants
• Scale hardware vertically or horizontally
• Improve processing architecture of the site

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Vertically and Horizontally Scaling a System

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Software for Web Servers

• Operating system tasks include running programs
  and allocating computer resources
• Linux
• Open-source operating system that is easy to
  install, fast, and efficient
• Open-source software
• Developed by a community of programmers who make
  it available for download at no cost

• The most popular Web server programs are
• Apache HTTP Server
• Microsoft Internet Information Server (IIS)
• Sun Java System Web Server (JSWS)
• Netcraft
• A networking consulting company in Bath, England
• Accumulates popularity rankings

Go to www.netcraft.com and check out some data
and surveys
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Solutions to the Spam Problem

• Reduce the likelihood that a spammer can
  automatically generate e-mail addresses
• Control exposure of an e-mail address
• Use multiple e-mail addresses
• Content filtering strategy
• Require software that identifies content elements
  that indicate if a message is (or is not) spam

• Content-filtering techniques
• Black list spam filter
• Looks for known spammer From addresses in
  incoming messages
• White list spam filter
• Examines From addresses and compares them to a
  list of known good sender addresses
• Challenge-response technique
• Compares all incoming messages to a white list

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Indexing and Searching Utility Programs

• Search engines or search tools
• Search either a specific site or the entire Web
  for requested documents
• Indexing program
• Can provide full-text indexing that generates an
  index for all documents stored on a server
• Can often index documents stored in many
  different file formats

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Data Analysis Software

• Web servers can capture
• Data about who is visiting a Web site
• How long the visitors Web browser viewed the
  site
• Date and time of each visit
• Which pages a visitor viewed
• Data captured by Web servers are stored in a log
  file

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Web Server Performance Evaluation

• Benchmarking
• Testing used to compare the performance of
  hardware and software
• Throughput
• Number of HTTP requests that a hardware and
  software combination can process in a unit of
  time
• Response time
• Time required by a server to process one request

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Load-Balancing Systems

• Load-balancing switch
• Piece of network hardware that monitors the
  workloads of servers attached to it
• Assigns incoming Web traffic to a server that has
  the most available capacity at that instant in
  time