Web Server

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Web Server

• Apache

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What is the Web Server?

• Web server is not a hardware platform, it is a
  software program allowing customers access in Web
  pages
• Web server is able to interpret requests HTTP
  arriving on the port using protocol HTTP, and
  respond with this same protocol
• -- In the Unix world this program is called
  an HTTP daemon
• -- In the Windows NT world the program is
  known as an http service

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Functions of the Web Server

• Provide access control, determining who can
  access particular directories or files on the Web
  server
• Run scripts and external programs to either add
  functionality to Web documents or provide
  real-time access to databases and other dynamic
  data
• Enable administration of both the server
  functions and the contents of the Web site
• Log transactions that the users make

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How a Web Server Works

• Information on web identified using a URL
• Uniform Resource Locator
• Browser requests information from the Web server
  combined with HTTP
• Hyper Text Transfer Protocol
• Web Server returns information to browser in HTML
  format
• Hyper Text Markup Language

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Internet
HTTP
Request http//www.ecomm.dal.ca/mec/index.htm
l
Web Sever
HTML
Response Welcome
Web Client (Browser)
Local File System
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Web Architecture
SEVER
Executable Portion
HTTP
Application Layer
Request
Web Sever
Server Script or Program
HTML
Response
Web Client (Browser)
Data Layer
Data Stores
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Web Servers are distinguished by

• Platforms Some are designed for Unix / Linux
  Platform, others for Windows NT, and others for a
  variety of platforms
• Performance There are significant differences in
  the processing efficiency of various servers, as
  well as the number of simultaneous requests they
  can handle and the speed with which they process
  those requests
• Security In addition to simple access control,
  some servers provide additional security services
  like support for advanced authentication.
• Commerce Some servers provide advanced services
  that support online selling and buying.

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Commercial Web Servers

• Apache Server
• Microsofts Internet Information Server (IIS)
• Netscapes Enterprise Server

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Introduction of Apache

• Apache is a free web server for modern operating
  systems including Unix / Linux and Windows NT. It
  is a secure, efficient and extensible server
  provides HTTP services in sync with the current
  HTTP standards.
• Apache is the leading internet web server, it has
  evolved from one of first web server programs
  --NCSA, and has been the most popular web server
  on the Internet since April of 1996.
• Apache-This word was developed from a patchy
  server

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The following websites use Apache or derivatives
Amazon. COM Yahoo! W3 Consortium Financial
Times Apple MP3.com Stanford etc.
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Versions of Apache

• Apache 0.62 -- was first public in April 1995
• Apache 1.0 -- issued in December 1995
• Apache 2.0 -- was released in April 2002
• New features of Apache 2.0
• filters, allow modules to process content
  generated by other modules they can encrypt,
  scan for viruses or compress not only static
  files but dynamically generated content
• Multi-protocol architecture, allows Apache to
  serve other protocols, such as POP3 and so on
• Improved support for non-Unix platforms, such as
  Windows, using the Apache Portable Runtime and
  platform-specific multi-processing modules
• Apache is regarded as having few known faults
  now, as soon as a
• bug or a fault of safety is detected, those are
  quickly corrected and a
• new version of the application is published

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Main Files of Apache

• httpd, the server program
• httpd.conf, main configuration file.
• /usr/local/apache/conf
• /etc/httpd/conf
• access_log, log of all accesses
• ../logs
• Error_log, log of all errors
• ../logs
• httppd.pid, contains process id of running server
  program

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Apache Configuration

• Apache is configured by placing directives in
  plain text configuration files. The main
  configuration file is usually called httpd.conf.
  The location of this file is set at compile-time,
  but may be overridden with the -f command line
  flag.
• The Apache Configuration Tool allows you to
  configure the /etc/httpd/conf/httpd.conf
  configuration file for your Apache Web server.
  Through the graphical interface, you can
  configure Apache directives such as virtual
  hosts, logging attributes, and maximum number of
  connections.

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How to Use Apache Configuration Tool

• Configure the basic settings under the Main tab
• Click on the Virtual Hosts tab and configure the
  default settings
• If you want to serve more than one URL or virtual
  host, add the additional virtual hosts
• Configure the server settings under the Server
  tab
• Configure the connections settings under the
  Performance Tuning tab
• Copy all necessary files to the Document Root and
  cgi-bin directories, and save your settings in
  the Apache Configuration Tool

Graphic interface under Unix / Linux
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Configure the Basic Server Settings

• Enter a fully qualified domain name that you have
  the right to use in the Server Name text area. It
  does not have to be the domain name resolved from
  the IP address of the server.
• Enter the email address of the person who
  maintains the Web server in the Webmaster email
  address text area.
• Use the Available Addresses area to define the
  ports on which Apache will accept incoming
  requests.
• Click the Add button to define additional ports
  on which to accept requests. A window as show as
  the below one Choose the Listen to all addresses
  option to listen to all IP addresses on the
  defined port specify a particular IP address
  over which the server will accept connections in
  the Address field, default port of http is 80
• Clicking the Edit button shows the same window as
  the Add button except with the fields populated
  for the selected entry.
• To delete an entry, select it and click the
  Delete button

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Security of Apache

• Security
• There are several solutions that provide
  secure transactions for Apache servers. This
  enables Apache servers to be used for ecommerce
  or other scenarios where sensitive information is
  exchanged (like credit card numbers).
• Authentication
• Authentication modules allow you to
  determine the identity of a client, usually by
  verifying an username and password against a
  backend database. Apache includes modules to
  authenticate against plain text and database
  files.
• Access Control
• Apache provides the mod_access module that
  can restrict access to resources based on
  parameters of the client request, such as the
  presence of a specific header or the IP address
  or hostname of the client. Third party modules
  allow you to restrict access to clients that
  misbehave, as explained in later sections on
  performance and bandwidth control.
• SSL/TLS
• The Secure Sockets Layer/Transport Layer
  Security protocols allow data between the Web
  server and client to be encrypted.

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Advantage

• The Apache license It is an open source, allows
  for both commercial and non-commercial uses of
  Apache
• Modular architecture Apache users can easily add
  functionality or tailor Apache to their specific
  environment
• Portable Apache runs on nearly all flavors of
  Unix (and Linux), Windows, mainframes...
• Robustness and security

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Disadvantage

• Less compatible with Windows system than some
  others

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Reference

• C. DiBona, S. Ockman, and M. Stone,1999, Open
  Sources Voice from the Open Source Revolution.
  Sebastopol, CA O'Reilly
• E. S. Raymond, The Cathedral and the Bazaar,
  http//www.tuxedo.org/esr/writings/cathedral-baza
  ar/
• P. Vixie, 1999Software Engineering, in Open
  Sources Voices from the Open Source Revolution,
  C. DiBona, S. Ockman, and M.Stone, Eds.
  Sebastopol, CA O'Reilly, 1999, pp. 91-100.
• Apache HTTP Server , Overview of New Features in
  Apache 1.3, 2003, http//httpd.apache.org/ docs/
  new_features_1_3.html
• Apache HTTP Server, Overview of New Features in
  Apache 2.0, 2003, http//httpd.apache.org/docs-2.
  0/new_features_2_0.html

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Thank You

• Deng Wei
• Oct, 2003

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Web Client

• Internet Explorer Netscape Navigator
• Issues request
• URL
• Get / Post MSG
• Display and Present data
• Support Scripting
• Java script
• VB script
• Support Programs
• Flash etc.
• Java applets

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Web Server

• Get request
• Locate data
• Send back data to client

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Executable Portion enable you to do

• Collect Information from the user and store the
  information on the server
• Perform tasks for the user such as placing an
  order for a product, performing complex
  calculations, or retrieving information from a
  database
• Identify a specific user and present an interface
  that is customized for him or her
• Present content that is highly volatile, such as
  Inventory, pending order, and shipment information

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Access Control

• Parameter of allow and deny control access
• Parameter of order control the implement order
  of allow and deny .
• If your setting is
• order allow, deny allow from all deny aaa.c
  om 
• In this way, all computers can be acceded,
  except which come from  aaa.com  On the
  contrary, If your setting as this 
• order deny, allow deny from all allow from 11.2
  3.44 
• It means all  accesses are denied, except
  11.23.44 IP(11.23.44.03/11.23.44.07 ) can be
  acceded