Chapter 8 Web Server Hardware and Software

Chapter 8: Web Server Hardware and Software

Web Server Basics ü The main job of a Web server computer is to respond to requests from Web client computers ü Three main elements of a Web server: ä Hardware ä Operating system software ä Web server software

Types of Web Sites ü Development sites ä Used to evaluate different Web designs ü Intranets ä Corporate networks that house internal memos, corporate policy handbooks, and a variety of other corporate documents ü Extranets ä Intranets that allow authorized parties outside the company to access information stored in the system ü Transaction-processing sites ä Commerce sites that must be available 24 hours a day, seven days a week ü Content-delivery sites ä Deliver content such as news, histories, summaries, and other digital information

Web Clients and Web Servers ü Client/server architectures ä Client computers typically request services ä A server processes the clients’ requests ü Web software ä Lets different types of computers running different operating systems communicate

Client Server Architecture and Software

Dynamic Content ü Dynamic content is nonstatic information constructed in response to a Web client’s request ü Dynamic page ä Web page whose content is shaped by a program in response to user requests ü Static page ä An unchanging page retrieved from disk ü Server-side scripting ä Programs running on a Web server create Web pages before sending them back to the requesting Web clients ü Dynamic page-generation technologies include: ä Active Server Pages (ASP) ä Java. Server Pages (JSP) ä PHP: Hypertext Preprocessor (PHP)

Various Meanings of “Server” ü Server ä Computer used to provide files or make programs available to other computers ü Server software ä Used by a server computer to make files and programs available to other computers ü Database server ä Server computer on which database management software runs

Server Architecture ü ü 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

Two-Tier Client/Server Architecture ü Two-tier client/server architecture has only one client and one server ü Request message ä Message that a Web client sends to request a file or files from a Web server ü Typical request message contains: ä Request line ä Optional request headers ä Optional entity body ü Request line ä Contains a command, the name of the target resource, and the protocol name and version number ü Request headers ä Can contain information about types of files that the client will accept in response to a request ü Entity body ä Used to pass bulk information to the server

Three-Tier and N-Tier Client/Server Architectures

Web Application Servers ü Software programs that provide the specific business functionality required of a web site. Include: Ø Catalog display Ø Transaction processing Ø Audio/video server Ø Auction server Ø B 2 B server APACHE has 62% of the market of Web server software Exercise: For more information, go to: www. apache. org

Right-sizing Your Hardware Platform: The Supply Side ü Scalability: the ability of a site to increase in size as demand warrants Ø Scale hardware vertically or horizontally Ø Improve processing architecture of the site

Vertically and Horizontally Scaling a System

Software for Web Servers ü Operating system tasks include running programs and allocating computer resources ü Linux ä Open-source operating system that is easy to install, fast, and efficient ü Open-source software ä Developed by a community of programmers who make it available for download at no cost ü The most popular Web server programs are: ä Apache HTTP Server ä Microsoft Internet Information Server (IIS) ä Sun Java System Web Server (JSWS) ü Netcraft ä A networking consulting company in Bath, England ä Accumulates popularity rankings Go to www. netcraft. com and check out some data and surveys

Solutions to the Spam Problem ü Reduce the likelihood that a spammer can automatically generate e-mail addresses ü Control exposure of an e-mail address ü Use multiple e-mail addresses ü Content filtering strategy ä Require software that identifies content elements that indicate if a message is (or is not) spam ü Content-filtering techniques ä Black list spam filter ä Looks for known spammer From addresses in incoming messages ä White list spam filter ä Examines From addresses and compares them to a list of known good sender addresses ä Challenge-response technique ä Compares all incoming messages to a white list

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

Data Analysis Software ü Web servers can capture: ä Data about who is visiting a Web site ä How long the visitor’s Web browser viewed the site ä Date and time of each visit ä Which pages a visitor viewed ü Data captured by Web servers are stored in a log file

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

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