1. Chapter 8: Web Server Hardware and Software

2. 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. 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. 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. 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. 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. 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. 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. 9 Two-Tier Client/Server Architecture Two-tier client/server architecture has one client and one server

10. 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. 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

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13. 13 Software for Web Servers Operating system tasks include running programs and allocating computer resources –Open-source software: Developed by a community of programmers who make it available for download at no cost Linux: Open-source operating system that is easy to install, fast, and efficient

14. 14 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

15. 15 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 the NCSA Apache has dominated the Web since 1996 because it is free (open source) and performs efficiently

16. 16 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

17. 17 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

18. 18 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

19. 19 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

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21. 21 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

22. 22 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

23. 23 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

24. 24 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

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26. 26 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

27. 27 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

28. 28 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

29. 29 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

30. 30 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

31. 31 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

32. 32 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

33. 33 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

34. 34 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

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37. 37 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

38. 38 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

39. 39 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