Chapter 8: Web Server Hardware and Software

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Chapter 8Web Server Hardware and Software
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Objectives

• In this chapter, you will learn about
• Web server basics
• Software for Web servers
• E-mail management and spam control issues
• Internet and Web site utility programs
• Web server hardware

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Web Server Basics

• The main job of a Web server is to respond to
  requests from Web client computers
• There are 3 components 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 request services
• A server processes the clients requests
• Web software is platform neutral, meaning that it
  lets different types of servers communicate with
  a variety of clients

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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

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Dynamic Content

• Server-side scripting (or includes)
• Programs running on a Web server create Web pages
  before sending them back to the requesting Web
  clients
• Dynamic page-generation technologies Server side
  scripts are combined with html tags to create
  dynamic content
• 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 to make files
  and programs available to other computers
• Database server Server on which database
  management software runs

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Two-Tier Client/Server Architecture

• Two-tier client/server architecture has one
  client and one server

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Two-Tier Client/Server Architecture

• Request message Message that a Web client sends
  to request a file or files from a Web server
• Typical request message contains
• 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

• Three-tier architecture
• Extends two-tier architecture to allow additional
  processing (e.g., collection of data from a
  database) before reponses to requests are made
• N-tier architectures
• Higher-order architectures
• Third tier includes software applications that
  interactively supply and update information to
  and from the web server

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Software for Web Servers

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

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Web Server Software

• 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

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Apache HTTP Server

• Apache is the results of an ongoing group
  software development effort, first developed by
  Rob McCool at the University of Illinois in 1994
  at the NCSA
• Apache has dominated the Web since 1996 because
  it is free (open source) and performs efficiently

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Microsoft Internet Information Server

• Comes bundled with current versions of Microsoft
  Windows Server operating systems
• Used on many corporate intranets
• Supports the use of
• ASP
• ActiveX Data Objects
• SQL database queries

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Sun Java System Web Server (Sun ONE, iPlanet,
Netscape)

• Descendant of the original NCSA Web server
  program
• Formerly sold under the names
• Sun ONE
• Netscape Enterprise Server
• iPlanet Enterprise Server
• Charges between 1400 and 5000 for the licensing
  fee

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Electronic Mail (E-Mail)

• We all know the benefits of email
• Email drawbacks include
• Time spent by business people responding to
  e-mail
• Computer viruses
• Programs that attach to other programs
• Can cause damage when the host program is
  activated
• Spam

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Spam

• Spam is unsolicited or commercial e-mail
• During one 24-hour period in 2005 researchers
  estimated that 106 billion spam e-mail messages
  were sent

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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
• Requires software that identifies content
  elements that indicate if a message is (or is
  not) spam

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Solutions to the Spam Problem

• 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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Web Site and Internet Utility Programs

• Finger
• Runs on UNIX operating systems
• Allows users to obtain information about other
  network users
• Command yields a list of users who are logged on
  to a network
• Ping (Packet Internet Groper)
• Tests connectivity between two computers
  connected to the Internet

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Tracert and Other Route-Tracing Programs

• Tracert (TRACE RouTe)
• Sends data packets to every computer on the path
  between one computer and another
• Clocks packets roundtrip times
• Calculates and displays the number of hops
  between computers
• Calculates the time it takes to traverse an
  entire one-way path between machines

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Telnet and FTP Utilities

• Telnet
• Program that allows users to log on to a computer
  connected to the Internet
• Telnet protocol
• Set of rules used by Telnet programs
• File Transfer Protocol (FTP)
• Defines formats used to transfer files between
  TCP/IP-connected computers

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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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Link-Checking Utilities

• Link checker examines each Web page and reports
  on URLs that
• Are broken
• Seem broken
• Are incorrect in some way
• Orphan file
• File on a Web site not linked to any page
• Dead link
• When clicked, it displays an error message rather
  than a Web page

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Remote Server Administration

• Web site administrator can control a Web site
  from any Internet-connected computer
• NetMechanic
• Offers a variety of link-checking, HTML
  troubleshooting, site-monitoring, and other
  programs

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Web Server Hardware

• Web server computers
• More memory, larger hard disk drives, and faster
  processors than typical PCs
• Blade servers
• Placing small server computers on a single
  computer board, then installing boards into a
  rack-mounted frame
• Virtual server (virtual host)
• Maintains more than one server on one machine

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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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Web Server Hardware Architectures

• Server farms
• Large collections of servers
• Centralized architecture
• Uses a few very large and fast computers
• Distributed/decentralized architecture
• Uses a large number of less powerful computers
• Divides the workload among them

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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

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Summary

• The Web uses a client/server architecture
• For simple HTTP requests a two-tier architecture
  works well
• Operating systems commonly used on Web server
  computers include
• Microsoft server operating systems
• UNIX-based operating systems

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Summary

• Utility programs running on Web server computers
  include
• Finger, Ping, Tracert, e-mail server software,
  Telnet, and FTP
• Unsolicited commercial e-mail (spam) has grown
  dramatically in recent years
• Content filters are becoming available to deal
  with the problem

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Summary

• Web server hardware
• Server computer must have enough memory and disk
  space
• Factors that affect Web server performance
  include
• Operating system
• Connection speed
• User capacity