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Chapter 8: Web Server Hardware and Software

Chapter 8: Web Server Hardware and Software. 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. Web Server Basics.

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Chapter 8: Web Server Hardware and Software

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  1. Chapter 8:Web Server Hardware and Software

  2. 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

  3. 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

  4. 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

  5. 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

  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

  7. 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)

  8. 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

  9. Two-Tier Client/Server Architecture • Two-tier client/server architecture has one client and one server

  10. 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

  11. 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

  12. 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

  13. 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 theNCSA • Apache has dominated the Web since 1996 because it is free (open source) and performs efficiently

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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

  29. 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

  30. 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

  31. 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

  32. 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

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