This document discusses web servers. It provides an overview of web clients and web servers, and describes how web servers handle static and dynamic content. The document outlines the typical architecture of a two-tier or three-tier client-server system for delivering web pages. It also discusses the GET and POST request methods, phases of request handling, popular web servers like Apache and IIS, and factors to consider when selecting a web server.

1. Web Servers
Sudan University for Science and Technology
College of graduate studies
Msc in Computer Science
Presented by
Mohamed Zeinelabdeen Abdelgader
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2. Presentation Outline
 An Over View
 Web Clients and Web Servers
 Dynamic & Static Content
 System Architecture
 Request methods.
 Accessing web servers
 Request Handling Phases
 Most Famous Web Servers
 Selecting a web server
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3. 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
 Many types of server
 FTP server : remote file space, often read-only
 Mail server : email system
 News server : newsgroups messages
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4. Web Clients and Web Servers
 Client/server architectures
 Client computers typically request services
 Server processes clients’ requests.
 Web server
 a computer program that delivers (serves) content, such as web
pages, using the Hypertext Transfer Protocol (HTTP), over the
World Wide Web.
 The term web server can also refer to the computer or virtual
machine running the program.
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5. Platform Neutrality of the Web
Lets different types of computers, running different operating systems,
communicate
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6. Static & Dynamic Content
 Static page
 Unchanging page retrieved from server
 Dynamic page
 Web page whose content is shaped by a program in
response to user requests
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7. Dynamic Content (cont)
 Server-side scripting
 Programs running on a Web server to create Web pages
before sending them back to the requesting Web clients
 Dynamic page-generation technologies
 Active Server Pages (ASP)
 JavaServer Pages (JSP)
 Hypertext Preprocessor (PHP)
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8. 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
 Request line
 Optional request headers
 Optional entity body
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9. Message Flows in a Two-Tier
Client/Server
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10. Two-Tier Client/Server Architecture (cont)
 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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11. Three-Tier or N-Tier Client/Server
Architectures
 Three-tier architecture
 Extends two-tier architecture to allow additional processing
 Third tier includes software applications that supply
information to the Web server
 Sometimes know as N-tier or multi-tier architectures
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12. Message Flows in a Three-Tier Client/
Server
Client tier Middle tier
Information tier
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13. Request methods (GET)
The get request sends form content as part of the URL .
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14. Request methods (POST)
The data sent in a post request are not part of the URL and cannot be
seen by the user.
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15. Accessing web servers
 Must know host name on which web server resides
 Remote web servers accessed using
Protocol Domain name
Page name
• URL: http://www.dtl.com/default.asp
• OR IP address http://207.60.134.230
 Local web servers (on same machine) accessed using
machine name or localhost
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16. Request Handling Phases
 URI to filename translation;
 Check access based on host address, and other
available information;
 Get an user id from the HTTP request and validate it;
 Authorize the user;
 Determine the Multipurpose Internet Mail Extensions
(MIME) type of the requested object (the content type,
the encoding and the language);
 Fix-ups (for example replace aliases by the actual path);
 Send the actual data back to the client;
 Log the request;
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17. Most Famous Web Servers
 Apache HTTP Server from Apache Software Foundation
 Internet Information Services (IIS) from Microsoft
 Sun Java Web Server from Sun Microsystems
 Formerly Sun ONE Web Server, iPlanet Web Server, and
Netscape Enterprise Server
 Zeus Web Server from Zeus Technology
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18. Apache HTTP Server
 Ongoing group software development effort
 Dominated the Web since 1996 because it is free and
performs efficiently
 Apache
 Developed by Rob McCool at the University of Illinois
in1994 at the National Center for Supercomputing
Applications (NCSA)
 Currently available on the Web at no cost as open-source
software
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19. 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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20. 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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21. Selecting a web server
Various criteria
Performance Reliability
e.g. how many client requests How robust is the web server?
per second can be How liable to crash? How easily
processed? Load balancing? recovered?
Support
Ease of Use
What support is
How easy to set up ,
provided by the
administer, learn?
vendor?
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22. Selecting a web server (cont.)
Price Security
How must does it cost to What security functionality
buy and maintain? is offered? e.g. Secure
Sockets Layer SSL?
Functionality
•server side techologies supported? Operating system
e.g. ASP? JSP? etc What operating system(s)
does the web server
support?
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23. Conclusion
 Web servers respond to client requests by providing
resources.
 A Web server is part of a multi-tier application. A multi-
tier application divides functionality into separate tiers.
The three-tier application contains an information tier, a
middle tier and a client tier.
 The most common HTTP request types are get and post.
 Selecting a web server depended on (Performance,
Reliability, Support, Functionality, Ease of Use, Price,
Security, Operating system).
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24. References
 Internet & World Wide Web How to Program (4nd
Edition)
 http://www.serverwatch.com/tutorials/article.php/1363221
 http://www.macronimous.com/resources/web_servers_demys
 http://www.w3.org/Servers.html
 http://en.wikipedia.org/wiki/Web_server
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