电子商务课件(7).ppt

1、Chapter 8:Web Server Hardware and Software,Electronic Commerce, Seventh Annual Edition,Electronic Commerce, Seventh Annual Edition,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 pr

2、ograms Web server hardware,Electronic Commerce, Seventh Annual Edition,3,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,Electronic Commerce, Sevent

3、h Annual Edition,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 acces

4、s information stored in the system,Electronic Commerce, Seventh Annual Edition,5,Types of Web Sites (continued),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 di

5、gital information,Electronic Commerce, Seventh Annual Edition,6,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,E

6、lectronic Commerce, Seventh Annual Edition,7,Electronic Commerce, Seventh Annual Edition,8,Dynamic Content,Dynamic content is nonstatic information constructed in response to a Web clients request Dynamic page Web page whose content is shaped by a program in response to user requests Static page An

7、unchanging page retrieved from disk,Electronic Commerce, Seventh Annual Edition,9,Dynamic Content (continued),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 Pag

8、es (ASP) JavaServer Pages (JSP) PHP: Hypertext Preprocessor (PHP),Electronic Commerce, Seventh Annual Edition,10,Various Meanings of “Server”,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 avail

9、able to other computers Database server Server computer on which database management software runs,Electronic Commerce, Seventh Annual Edition,11,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

10、 to request a file or files from a Web server Typical request message contains: Request line Optional request headers Optional entity body,Electronic Commerce, Seventh Annual Edition,12,Electronic Commerce, Seventh Annual Edition,13,Two-Tier Client/Server Architecture (continued),Request line Contai

11、ns 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,Electronic Commerce, Seventh Annual Editio

12、n,14,Three-Tier and N-Tier Client/Server Architectures,Three-tier architecture Extends two-tier architecture to allow additional processing N-tier architectures Higher-order architectures Third tier includes software applications that supply information to the Web server,Electronic Commerce, Seventh

13、 Annual Edition,15,Electronic Commerce, Seventh Annual Edition,16,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 o

14、f programmers who make it available for download at no cost,Electronic Commerce, Seventh Annual Edition,17,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 c

15、ompany in Bath, England Accumulates popularity rankings,Electronic Commerce, Seventh Annual Edition,18,Apache HTTP Server,Apache is an ongoing group software development effort It has dominated the Web since 1996 because it is free and performs efficiently Apache Developed by Rob McCool at the Unive

16、rsity of Illinois in1994 at the NCSA Currently available on the Web at no cost as open-source software,Electronic Commerce, Seventh Annual Edition,19,Microsoft Internet Information Server,Comes bundled with current versions of Microsoft Windows Server operating systems Used on many corporate intrane

17、ts Supports the use of: ASP ActiveX Data Objects SQL database queries,Electronic Commerce, Seventh Annual Edition,20,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 En

18、terprise Server Charges between $1400 and $5000 for the licensing fee,Electronic Commerce, Seventh Annual Edition,21,Electronic Mail (E-Mail),Being able to attach documents to e-mail is useful Drawbacks include: Time spent by business people responding to e-mail Computer viruses Programs that attach

19、 to other programs Can cause damage when the host program is activated,Electronic Commerce, Seventh Annual Edition,22,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 Companies now offer software to

20、limit the amount of spam,Electronic Commerce, Seventh Annual Edition,23,Electronic Commerce, Seventh Annual Edition,24,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 Co

21、ntent filtering strategy Require software that identifies content elements that indicate if a message is (or is not) spam,Electronic Commerce, Seventh Annual Edition,25,Solutions to the Spam Problem (continued),Content-filtering techniques Black list spam filter Looks for known spammer From addresse

22、s 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,Electronic Commerce, Seventh Annual Edition,26,Web Site and Internet Utility Programs,Finger Ru

23、ns 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,Electronic Commerce, Seventh Annual Edition,27,Trac

24、ert 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 bet

25、ween machines,Electronic Commerce, Seventh Annual Edition,28,Electronic Commerce, Seventh Annual Edition,29,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) De

26、fines formats used to transfer files between TCP/IP-connected computers,Electronic Commerce, Seventh Annual Edition,30,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

27、 indexing that generates an index for all documents stored on a server Can often index documents stored in many different file formats,Electronic Commerce, Seventh Annual Edition,31,Data Analysis Software,Web servers can capture: Data about who is visiting a Web site How long the visitors Web browse

28、r 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,Electronic Commerce, Seventh Annual Edition,32,Link-Checking Utilities,Link checker examines each Web page and reports on URLs that: Are broken Seem broken Are incorrect i

29、n 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,Electronic Commerce, Seventh Annual Edition,33,Remote Server Administration,Web site administrator can control a Web site from any Internet-connected computer

30、NetMechanic Offers a variety of link-checking, HTML troubleshooting, site-monitoring, and other programs,Electronic Commerce, Seventh Annual Edition,34,Web Server Hardware,Web server computers More memory, larger hard disk drives, and faster processors than typical PCs Blade servers Placing small se

31、rver 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,Electronic Commerce, Seventh Annual Edition,35,Web Server Performance Evaluation,Benchmarking Testing used to compare the performanc

32、e 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,Electronic Commerce, Seventh Annual Edition,36,Web Server Hardware Architectures,Server farms or server

33、cluster is a collection of computer servers usually maintained by an enterprise to accomplish server needs far beyond the capability 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,Electronic Commerce, Seventh Annual Edition,37,Load-Balancing Systems,Load-balancing switch Piece of network h