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. The three main elements of a Web server are the: –Hardware –Operating system software –Web server software

3. Types of Web Sites An important first step in planning a Web server is to determine what the company wants to accomplish with the server. The company must estimate how many visitors will be connecting to the Web site and what types of files will be delivered through the site. Companies create Web sites in a wide variety of forms including –Development sites –Intranets –Extrants –Information-only sites for customers –Transaction-processing sites (B2B or B2C sites) –Content-delivery sites.

4. Development Sites The simplest Web site and the least costly to implement is a development site. A development site can reside on an existing PC and can be developed with low-cost Web site building tools, such as Microsoft FrontPage or Macromedia Dreamweaver. Testers can access the site through their PCs on the existing LAN.

5. Intranets Corporate intranets house internal memos, corporate policy handbooks, expense account worksheets, budgets, newsletters, and a variety of other corporate documents. Intranets are shielded from the Internet; they do not require additional security software to protect them against threats from outside the company.

6. Extranets Extranets are intranets that allow certain authorized parties outside the company to access certain parts of the information stored in the system.

7. Transaction-Processing Sites Transaction-processing sites, such as business-to- business and business-to-consumer electronic commerce sites must be available 24 hours a day, seven days a week; that is, they must be high- reliability servers. Transaction-processing sites must also have spare server computers to handle high traffic volumes. Transaction-processing sites must also run security software.

8. Content-Delivery Sites Content-delivery sites deliver content such as news, histories, summaries, and other digital information. Content must be presented rapidly on the visitor ’ s screen. Visitors must be able to locate articles quickly with a fast and precise search engine.

9. Web Clients and Servers Internet connections that are part of the Web become Web client computers on a worldwide client/server network. Client/server architectures are used in LANs, WANs, and the Web. Web software is platform neutral, letting computers communicate with each other easily.

10. Platform Neutrality of the Web

11. Dynamic Content Dynamic content is nonstatic information constructed in response to a Web client ’ s request. Server-side technologies (server-side includes, server-side scripting) are programs running on the Web server to create the Web pages before sending them back to the client. ASP(Active Server Page), JSP(Java Server Page), and PHP(Hypertext Preprocessor) are server-side scripting mechanisms that build dynamic sites and Web applications.

12. The Future of Dynamic Web Page Generation The Apache Cocoon Project is an initiative where content is stored with XML tags that describe the meaning of each content item. Instead of creating a Web page, Cocoon can produce a response tailored to the request by applying a style sheet to the data. Other similar efforts are underway from Microsoft (.NET framework) and Oracle.

13. Various Meanings of “ Server ” Server – any computer used to provide files to other computers connected to it through a network. Sometimes included in that meaning, however, are: –Server software –Database server –It is important to ask qualifying questions when determining what one might mean by “ server ”.

14. Two-Tier Client/Server Architecture

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

16. Operating Systems for Web Servers A computer must have an operating system to run programs as well as keep track of multiple users logged on to the system to ensure that they do not interfere with one another. The most common operating systems for Web servers from Microsoft are: Windows NT Server, Windows 2000 Advanced Server, and Microsoft.NET. Unix-based products are also popular: Linus, Solaris, and FreeBSD

17. Web Server Software The most popular Web server programs in use today: –Apache HTTP Server –Microsoft Internet Information Server (IIS) –Sun Java System Web Server 6.1 (formerly known as Sun One or iPlanet Enterprise Server)

18. Apache HTTP Server Free and performs efficiently. Runs on many operating systems and the hardware that supports them. Has a built-in search engine and HTML authoring tools and supports FTP. Can be managed from either a server console or a Web server.

19. http://www.apache.org

20. Microsoft Internet Information Server (IIS) Comes bundled with Microsoft ’ s Windows 2000 Server operating systems. Includes an integrated search engine. Permits administration from a remote server. Combines HTML pages, ActiveX components, and scripts to produce dynamic pages.

21. http://www.microsoft.com/WindowsServer2003/iis/default.mspx

22. Sun Java System Web Server 6.1 Sun ONE (iPlanet, Netscape) Web Server Formerly sold under the names Netscape Enterprise Server and iPlanet Enterprise Server. Runs on many operating systems, including HP-UX, Solaris, and Windows. Its management tools allow administrators to manage users and monitor server activity interactively.

23. http://wwws.sun.com/software/products/web_srvr/home_web_srvr.html

24. Web Site and Internet Utility Programs Finger is a program that runs on UNIX operating systems and allows users to obtain information about other network users. –Many organizations have disabled Finger commands for privacy and security reasons. Ping (Packet Internet Groper) tests the connectivity between two computers connected to the Internet. Tracert (TRACE RouTe) sends data packets to every computer on the path (Internet) between computers and clocks the packet ’ s round-trip times.

25. Electronic Mail Originated in the 1970 ’ s on the ARPANET. Used in business to convey messages within seconds, there are many benefits to using email. There are also drawbacks: –Spam or junk mail: Wastes time and disk space Often contains offensive content that poses risks for employers –Viruses: Can be carried by email and infect entire systems –Time Business people can spend up to two hours a day responding to messages

26. Telnet and FTP Utilities Telnet allows users to log on to a computer that is connected to the Internet. FTP, File Transfer Protocol, is the part of the TCP/IP rules that defines the formats used to transfer files between TCP/IP computers. –Can transfer files one at a time, or several at once –Displays remote and local computers ’ directories –Has built-in error controls to copy files accurately

27. WS_FTP:

28. Indexing and Searching Search engine and indexing programs are important elements of many Web servers. Search engines, or search tools, search either a specific site or the entire Web for requested documents. An indexing program can provide full-text indexing that generates an index for all documents stored on a server.

29. Data Analysis Web servers can capture visitor information, including data about who is visiting a Web site, how long the visitor ’ s Web browser viewed the site, the date and time of each visit, and which pages were displayed. Two of the most popular Web log file analysis programs are the Analog Web server log file analyzer and the WebTrends Web server log file analyzer. –Others: Analog, Keylime Software, Urchin Web Analytics, Web Side Story, Web Trends.

30. Link Checking A link checker examines each page on the site and reports on any URLs that are broken, that seem to be broken, or that are in some way incorrect. An orphan file is a file on a Web site that is not linked to any page. Other important site management features include script checking and HTML validation. A dead link, when clicked, displays an error message rather than a Web page.

31. Link Checking Free link-checking and Web site validation programs, such as Elsop Linkscan, can be launched by entering the address of a Web site ’ s home page and checking a few boxes. Commercial site checkers, such as Big Brother software from Watchfire, produce more comprehensive results and more detailed site analyses than do the free products.

32. Link Checking

33. Remote Server Administration With remote server administration, a Web site administrator can control a Web site from any Internet-connected computer. Although all Web sites provide administrative controls, it is convenient for an administrator to be able to fix the server from wherever he or she happens to be.

34. Remote Server Administration Tool

35. http://www.netmechanic.com/toolbox/html-code.htm

36. Web Server Hardware The fundamental job of a Web server is to process and respond to Web client requests sent using HTTP. Web server computers have more memory, larger and faster hard disk drives, and faster processors than typical desktop or notebook PCs. A virtual server, or virtual host, is a feature that maintains more than one server on one machine.

37. Web Server Performance Evaluation Benchmarking is a form of testing used to compare the performance of hardware and software. Hardware and operating systems are key areas for benchmarking. The speed of its connection can affect a Web server ’ s performance. Throughput and response time can be used to measure a server ’ s Web page delivery capability.

39. Web Server Hardware Architectures Large electronic commerce Web sites must deliver millions of individual Web pages every day. They must also process thousands of customer and vendor transactions each day. The large collection of servers that these sites have are called server farms.

40. Web Server Hardware Architectures One approach to Web server architecture is called a centralized architecture, which uses a few very large and very fast computers. Another approach is a decentralized architecture, which uses a large number of servers. Most large decentralized sites use load-balancing systems.

41. Load-Balancing Systems A load-balancing switch is a piece of network hardware that monitors the workloads of the servers attached to it and assigns incoming Web traffic to the server that has the most available capacity. In a simple load-balancing system, the traffic that enters the site from the Internet, encounters the load- balancing switch, which then directs the traffic to the Web server best able to handle the traffic.

42. Load-Balancing System Architecture

43. Complex Load-Balancing

44. Web Hosting Choices When making Web server hosting decisions, a company should ask whether the hardware, or platform and software combination, can be upgraded when the traffic on its site increases. Using a service provider ’ s shared or dedicated hosting services instead of building an in-house server or using a co-location service means that the staffing burden shifts from the company to the Web host.