Chapter 8 web server hardware and software
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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 l.jpg

Chapter 8:Web Server Hardware and Software


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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 is to respond to requests from Web client computers

  • There are 3 components 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

  • 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 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


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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

  • 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)


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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 to make files and programs available to other computers

      • Database server: Server on which database management software runs


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Two-Tier Client/Server Architecture

  • Two-tier client/server architecture has one client and one server


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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


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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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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 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


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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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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


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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


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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

    • Requires software that identifies content elements that indicate if a message is (or is not) spam


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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


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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

  • 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

  • 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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