chapter 8
TRANSCRIPT
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Chapter 8:
Web Server Hardware and Software
Electronic Commerce, Seventh Annual
Edition
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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 programs
• Web server hardware
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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
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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
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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 digital information
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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
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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
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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 Pages (ASP)
– JavaServer Pages (JSP)
– PHP: Hypertext Preprocessor (PHP)
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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 available to other computers
• Database server– Server computer on which database management
software runs
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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 to request a file
or files from a Web server
• Typical request message contains:– Request line
– Optional request headers
– Optional entity body
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Two-Tier Client/Server Architecture (continued)
• 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
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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
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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 of programmers who
make it available for download at no cost
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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
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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 University of Illinois in1994 at the NCSA
– Currently available on the Web at no cost as open-source software
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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
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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
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Electronic Mail (E-Mail)
• Being able to attach documents to e-mail is useful
• Drawbacks include:– Time spent by business people responding to e-
– Computer viruses
• Programs that attach to other programs
• Can cause damage when the host program is activated
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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 limit the amount of spam
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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
– Require software that identifies content elements that indicate if a message is (or is not) spam
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Solutions to the Spam Problem (continued)
• 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
• CAN-SPAM law– http://www.ftc.gov/bcp/edu/pubs/business/ecommerce/bus61.shtm
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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
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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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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
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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
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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
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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
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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
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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
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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
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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
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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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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
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Summary (continued)• 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
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Summary (continued)
• 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