BSAD 372 SPRING 2017 CH 8
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The document discusses web servers, including how they perform basic functions through client-server architectures. A web server's main job is to respond to requests from web clients using hardware, an operating system, and web server software. Dynamic content is generated through server-side scripting programs that create customized pages in response to user requests. The terms "server" can refer to different types of computers and software providing various resources over a network.
BSAD 372 SPRING 2017 CH 8
- 1. Web Server Hardware and Software CHAPTER 8 © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. .
- 2. Learning Objectives In this chapter, you will learn: • How a Web server performs its basic functions • What operating system and server software is used on Web servers • How to identify and manage e-mail and spam control issues • How commonly used Internet and Web site utility programs work • What hardware online businesses use to power their Web sites • How cloud computing and content delivery networks are providing new Web infrastructure © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 22
- 3. Introduction • Case study: Israel’s Channel 2 News – Produces news content and programming for other Channel 2 shows, Web sites and its mobile device app • Web site and mobile app offer many high-resolution photographs and video chips – Online news organizations face wide variation in user interest levels and need for Internet bandwidth • Breaking news events lead to high demands on the Web site and mobile app and can result in system overload • Peak periods in news business can be unpredictable • As a solution, Channel 2 uses Google Cloud Computing to store content © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 3
- 4. Web Server Basics • Client/server architectures used in LANs, WANs, Web – Server computers have more memory and larger, faster disk drives than the client computers they serve • Web browser: a type of Web client software • Platform neutrality is the ability of a network to connect devices using different operating systems – Critical in rapid spread, widespread Web acceptance • Web server’s main job to respond to Web client requests – Main elements: Hardware, operating system software, and Web server software © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 4
- 5. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 5 FIGURE 8-1 Platform neutrality of the Web ©CengageLearning2017
- 6. Dynamic Content Generation • Static page is an unchanging page retrieved from stored Web server file(s) • Dynamic page created in response to user request – Customized pages give user an interactive experience • Client-side scripting software operates on the Web client (browser) and changes Web page display in response to a user’s actions (JavaScript or Adobe Flash) • Server-side scripting program runs on a Web server and creates Web page in response to request for specific information from a Web client © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 6
- 7. Dynamic Content Generation (cont’d.) • Software tools to create dynamic Web pages – Microsoft ASP.NET, Apache Software Foundation Hypertext Preprocessor (PHP) and Adobe ColdFusion – AJAX (asynchronous JavaScript and XML) creates interactive Web sites that look like applications • Ruby on Rails, Scala and Python (scripting language) are used to accomplish the same objectives • Many Web sites use more than one language and/or development framework to accomplish specific objectives © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 7
- 8. Multiple Meanings of “Server” • Server is any computer providing files or making programs available to other computers connected to it through a network – Server software makes files and programs available • May be part of the operating system (OS) and be referred to as server software (confusing) • Some servers connected to Internet via a router – Runs Web server software that makes server’s files available to other computers and called a Web server • E-mail server: handles incoming and outgoing e-mail © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 8
- 9. Multiple Meanings of “Server” (cont’d.) • Database server runs database management software • Transaction server runs accounting and inventory management software • “Server” describes several types of computer hardware and software – Context needed to determine the intended meaning © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 9
- 10. Web Client/Server Architectures • Web browser requests files from Web server and uses the Internet as the transportation medium – Request formatted by browser using HTTP and sent to server computer – Server receives request, retrieves requested Web page file, formats using HTTP, and sends back to client over the Internet – Client Web browser software displays page • Repeating process of request, response, display • Web page with graphics can be slow because each page element requires separate request and response © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 10
- 11. Web Client/Server Architectures (cont’d.) • Basic model is two-tier client/server architecture – One client and one server computer • Request message is the Web client message sent to request file(s) from a Web server that consists of three major parts – Request line contains command, target resource name, protocol name, version number – Optional request headers contain file type information client accepts – Optional entity body is used to pass bulk information to server © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 1111
- 12. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 12 FIGURE 8-2 Message flows in a two-tier client/server network ©CengageLearning2017
- 13. Web Client/Server Architectures (cont’d.) • Server receiving request message executes command included in message – Retrieves Web page file from disk and creates a response message to send back to client – Identical in structure to request message (slightly different function) • Response header line indicates server HTTP version, response status, status information explanation • Response header field returns information describing server’s attributes • Entity body returns HTML page requested by the client machine © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 13
- 14. Web Client/Server Architectures (cont’d.) • Three-tier architecture allows additional processing before server responds to client’s request – Often includes databases and related software applications that supply information to the Web server • Web server uses software applications’ output when responding to client requests • N-tier architectures have more than three tiers – Track customer purchases stored in shopping carts – Look up sales tax rates, ;keep track of customer preferences, update in-stock inventory databases – Keep product catalog current © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 14
- 15. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 15 FIGURE 8-3 Message flows in a three-tier client/server network ©CengageLearning2017
- 16. Operating Systems for Web Servers • Operating system tasks include running programs, allocating computer resources to programs, and proving input and output services – Required for a computer to run programs – Larger system responsibilities include tracking multiple users, ensuring no interference • Web server operating systems software run on Microsoft Windows Server products, Linux or UNIX- based operating systems © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 16
- 17. Operating Systems for Web Servers (cont’d.) • Some companies consider Microsoft operating system simpler to use than UNIX based systems – Some concerns about security weaknesses caused by tight integration of Microsoft products • Linux is open-source, fast, efficient, easy to install – Can be downloaded free from the Web but most companies buy it through a commercial distributor for the additional utilities and support • Mandriva, Red Hat, SuSE Linux Enterprise • Oracle sells Web server hardware with its UNIX- based operating system Solaris © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 1717
- 18. Web Server Software • Commonly used programs are Apache HTTP Server and Microsoft Internet Information Server (IIS) – Some businesses, such as Google, wrote their own • Apache dominant Web server software since 1996 – Free and user-supported with other services available • Microsoft IIS bundled with Microsoft Windows Server OS and runs only on Windows systems – Used on many intranets, and small and large sites that have adopted Microsoft products as standard – ISS is free but OS it comes with can be expensive © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 18
- 19. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 19 FIGURE 8-4 Percent of active Web sites that use major Web server software products
- 20. Electronic Mail (E-Mail) and E-Mail Benefits and Drawback • E-mail used to gather information, execute transactions and perform electronic commerce tasks • Reason people originally attracted to the Internet – Conveys messages in seconds with attachments often the most important message part – Most popular form of business communication • Drawbacks include the time spent answering e-mails – Burdensome and can take 2 hours per day • Email attachments can be or contain a computer virus • Most frustrating and expensive problem is spam © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 20
- 21. Spam and Solutions to the Spam Problem • In 2009, the peak year for spam, one 24-hour period showed 220 billion spam e-mail messages sent • Spam growth has leveled off and legal and technical solutions will continue to reduce it • Benefits reaped by spammers still make it attractive – Reducing spam approaches require passing laws and technical changes in Internet mail-handling systems – Approaches under existing laws and technologies require cooperation by organizations – Some tactics can be taken by individual e-mail users © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 21
- 22. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 22 FIGURE 8-5 Spam as a proportion of all business e-mail
- 23. Individual User Antispam Tactics • Using a complex e-mail address reduces the chance that a spammer can automatically generate it – Downside is that a complex address can be hard to remember • Control e-mail address exposure – Spammer software robots search for e-mail addresses on discussion boards, in chat rooms, other online sources that use email • Use multiple e-mail addresses – Switch to another if spammers use one • Use filtering techniques based on contents © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 23
- 24. Basic Content Filtering • Content-filtering techniques differ in terms of content elements examined, spam indications and how strictly message classification rules applied • Basic content filters examine e-mail headers – Client-level filtering: individual users’ computers – Server-level filtering: mail server computers • Black list spam filter looks for known spammers in incoming messages’ From addresses • White list spam filter looks for good sender From addresses in incoming messages – High false positives rate © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 24
- 25. Challenge-Response Content Filtering • Compares all incoming messages to a white list – If sender is not on the white list, automated e-mail response sent (challenge) – Challenge asks sender to reply to e-mail (response) – Reply must contain response to a challenge presented in the e-mail • Designed so human can respond easily • More information – Carnegie Mellon University CAPTCHA Project site • Drawback is potential abuse © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 25
- 26. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 26 FIGURE 8-6 Example of a challenge that uses distorted letters and numbers ©CengageLearning2017
- 27. Advanced Content Filtering • Looks for spam indicators in entire e-mail message – Indicator identified: message’s spam “score” raised • Indicator types are words, word pairs, certain HTML codes, information about where word occurs – Spammers stop including defined indicators • Bayesian revision statistical technique uses additional knowledge to revise earlier probability estimates – Naïve Bayesian filter software allows users to review messages and indicate if message is spam (not spam) – Software gradually learns to identify spam and is correct about 95% of the time after training © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 27
- 28. Legal Solutions • January 2004: U.S. CAN-SPAM law went into effect – Spam decreased first two months, but returned to previous levels after no threat of federal prosecution – Prohibits misleading e-mail message address header information, deceptive subject headers and transfer of email addresses • Some spammers have been prosecuted, fined and received jail time – Many use servers outside U.S. (jurisdiction issues) • Legal solutions have had only limited success – Expensive to prosecute spammers © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 28
- 29. Technical Solutions • Internet design did not include mechanisms ensuring e-mail sender identity would be know to recipient • Internet’s communication protocol designed to be a polite set of rules where a sending computer waits for acknowledgement that message was received – Originating computer will slow if acknowledgement is delayed (must continue to scan for it) and will not send more messages until acknowledgment received – Defending (receiving) company must develop way to identify computers sending spam and delay acknowledgement © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 29
- 30. Technical Solutions (cont’d.) • Computer being spammed can also launch a return attack called teergrubing (“tar pit”) – Send e-mail messages back to suspected spamming computer with the objective of setting a trap that drags down its ability to send spam – Concern is that counterattack might violate laws • Ultimate spam solution could come from new e-mail protocols providing absolute verification of e-mail message source • Currently most effective solutions have been coordinated efforts to identify and block spammers © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 30
- 31. Web Site Utility Programs • TCP/IP supports utility programs (tools) – Run on Web server or client computers • E-mail: earliest Internet utility program – Most important utility – Key element in electronic commerce strategies © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 31
- 32. Tracert and Other Route-Tracing Programs • Tracert (TRACE RouTe) sends data packets to every computer on path between one computer and another and clocks packets’ round-trip times – Provides indication of time message needs to travel from one computer to another and back – Ensures remote computer online and pinpoints data traffic congestion – Calculates and displays the number of hops between computers and time to traverse entire one-way path © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 32
- 33. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 33 FIGURE 8-7 Tracing a path between two computers on the Internet ©CengageLearning2017
- 34. Telnet and FTP Utilities and Indexing and Searching Utility Programs • Telnet program allows a person using one computer to access files and run programs on a second computer connected to the Internet • File Transfer Protocol (FTP) is the part of the TCP/IP rules that defines formats used to transfer files between TCP/IP connected computers • Search engines and indexing programs are important elements of many Web servers – When a browser requests a Web site search, engine compares index terms to the requester’s search terms to find matching documents © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 34
- 35. Data Analysis Software • Web servers capture visitor information and places it into a Web log file (grows quickly) • Third-party Web log file analysis programs summarize information in the file – Query log file and return gross summary information or accumulating details • Popular Web log file analysis programs – Adobe Analytics, Google Analytics, WebTrends © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 35
- 36. Link-Checking Utilities • Dead link displays an error message rather than Web page when clicked – Sites with many dead links are said to have link rot • Link checker utility examines each site page and reports URLs that no longer exists – Identifies orphan files which are files on Web server not linked to a page – Also includes script checking and HTML validation – Adobe Dreamweaver includes link-checking program – Free standing link-checking programs include Elsop LinkScan and LinxCop © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 36
- 37. Remote Server Administration • Web site administrator controls Web site from any Internet connected computers – Monitor server activity and manipulate server from wherever administrator happens to be • LabTech Software includes remote administration, link-checking, HTML troubleshooting, site-monitoring and other utility programs – Useful in managing the operations on the Web © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 37
- 38. Web Server Hardware • Wide variety of computer brands, types, sizes used by organizations to host online operations • Small companies run Web sites on desktop PCs • Most online business operations are operated on computers designed for site hosting • Businesses select specific hardware and software elements based on site’s functionality, expected visitors, number and size of pages and graphics © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 38
- 39. Server Computers • Generally have more memory, larger (faster) hard disk drives and faster processors than typical desktop computers – Many Web server computers use multiple processors – Most companies spend $2,000-$50,000 on an individual Web server with large organizations spending millions on server hardware • May be housed in freestanding cases but most are installed in equipment racks • Blade servers are servers-on-a-card – Small in size: 300 installed in single 6-foot rack © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 39
- 40. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 40 FIGURE 8-8 Rack-mounted blade servers
- 41. Web Servers and Green Computing • Significant electrical power needs for operating servers and cooling the room where servers housed • Green computing is efforts to reduce environmental impact of large computing installations • Novel approaches using natural cooling – Google server facility in Finland – Facebook server in Lulea, Sweden – Other companies: Hewlett-Packard, FedEx, Harris Corporation © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 41
- 42. Web Server Performance Evaluation • Benchmarking is testing to compare hardware and software performance and includes many elements – Hardware, operating system software, server software, connection speed, user capacity, type of Web pages delivered and connection bandwidth – Users server can handle important, hard to measure • Throughput is the number of HTTP requests hardware and software process in a unit of time • Response time is time server requires to process one request • Independent testing and benchmarks available © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 42
- 43. Web Server Hardware Architectures • Electronic commerce Web sites use tiered architecture to divide work of serving Web pages – May use more than one computer within each tier • Server farms are large collections of servers lined up row after row • Centralized architecture uses a few expensive, fast computers and more sensitive to technical problems – Requires adequate backup plans © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 43
- 44. Web Server Hardware Architectures (cont’d.) • Distributed architecture (decentralized architecture) uses many less-powerful, less-expensive computers – Spreads risk over large number of servers – Requires additional hubs or switches to connect servers to each and the Internet – Requires cost of load balancing to assign the workload efficiently © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 44
- 45. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 45 FIGURE 8-9 Centralized and decentralized Web site architectures ©CengageLearning2017
- 46. Load-Balancing Systems • Load-balancing switch is network hardware that monitors server workloads and assigns incoming Web traffic to the server with most available capacity – Simple load-balancing system traffic enters through site’s router and encounters load-balancing switch which directs traffic to best Web server – More complex load-balancing systems incoming Web traffic directed to groups of dedicated Web servers • Groups organized by specific functions • Cost of load-balancing systems range from about $2,000 (simple) to $15,000 - $40,000 (complex) © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 46
- 47. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 47 FIGURE 8-10 Basic load-balancing system ©CengageLearning2017
- 48. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 48 FIGURE 8-11 Complex load balancing system ©CengageLearning2017
- 49. Cloud Computing • To reduce costs and effort many businesses are outsourcing entire networks using cloud computing – Allows multiple organizations to share a network of servers and software giving businesses access to computers, storage and backup at lower cost – Sometimes called infrastructure as a service (IaaS) or platform as a service (PaaS) – Resources can be allocated dynamically as needed • Some larger firms use hybrid cloud computing – Move large-volume, routine work to cloud provider and maintain more sensitive data and processes internally © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 49
- 50. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 50 FIGURE 8-12 Cloud computing provider global market share, 2015 © Cengage Learning 2015
- 51. Content Delivery Networks • Latency occurs when a transmission delay is caused by network inability to handle full traffic load – Problem for businesses that rely on Internet to deliver large audio and video files to customers • To prevent latency, online businesses have turned to content delivery networks – Service that stores large file contents on multiple servers throughout the Internet for a fee – Large file requests routed to nearest server with a stored copy of the file © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 51
- 52. © 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use. 52 FIGURE 8-13 Growth of Internet traffic, actual and projected