1. Chapter 8: Web Server Hardware and Software

2. 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

3. Types of Web Sites Used to evaluate different Web designs
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

4. 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

5. Client Server Architecture and Software

6. Dynamic Content
Dynamic content is nonstatic information constructed in response to a Web client’s 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)

7. Various Meanings of “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

8. 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

9. 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

11. Three-Tier and N-Tier Client/Server Architectures

12. 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:

13. 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

14. Vertically and Horizontally Scaling a System

15. 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 and check out some data and surveys

16. Solutions to the Spam Problem
Reduce the likelihood that a spammer can automatically generate addresses
Control exposure of an address
Use multiple 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

17. 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

18. Data Analysis Software
Web servers can capture:
Data about who is visiting a Web site
How long the visitor’s 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

19. 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

20. 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