1. Technology in Action Chapter 13 Behind the Scenes: How the Internet Works Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall

2. The Management of the Internet Ownership of the Internet –Local networks are owned by Individuals Universities Government agencies Private companies –Infrastructure (high-speed data lines) is owned by Government entities Privately held companies Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall1

3. The Management of the Internet (cont.) Management the Internet –Nonprofit organizations and user groups Each have a specialized purpose Previously handled by U.S. government contractors –Changed because of global nature of the Internet Guarantees worldwide engagement in the direction of the Internet Paying for the Internet –National Science Foundation (NSF) Pays for large part of infrastructure Funds research and development for new technologies Through federal taxes –Other countries participate as well Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall2

4. The Management of the Internet (cont.) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall3

5. Internet Networking Internet Data Routes How computers are connected to the Internet –Internet is a “network of networks” Similar to U.S. highway system –Main paths known collectively as the Internet backbone Large national and international networks Owned by commercial, education, or governmental organizations –Have fastest connections –Bandwidth needs determine what kind of line is used Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall 4

6. Internet Networking Internet Data Routes (cont.) How individuals connect to an ISP –Point of presence (POP) A bank of modems, servers, routers, and switches Many users can connect simultaneously –ISPs maintain multiple POPs throughout the geographic area they serve Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall5

7. Internet Networking The Network Model of the Internet The network model the Internet uses –Client/server model –Clients are Devices such as computers, tablets, and smartphones Clients use browsers to request services Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall6

8. Internet Networking The Network Model of the Internet (cont.) The network model the Internet use (cont.) –Types of servers Web servers: Run specialized operating systems to host web pages and other information Commerce servers: Software that enables users to buy goods and services; use security protocols to protect sensitive information File servers: Provide remote storage; cloud storage Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall7

9. Data Transmission and Protocols Network follows standard protocols to send information Protocol is a set of rules for exchanging electronic information Could be considered the rules of the road for the information superhighway –Open systems – the design of protocol is made public for access by anyone –Proprietary system – private system which was the norm Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall8

10. Data Transmission and Protocols (cont.) Problems in developing an open system Internet protocol –Agreeing on standards was easy –Developing a new method of communication was tough Circuit switching (technology available in the 1960s) was inefficient for computer communication Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall9

11. Data Transmission and Protocols Circuit Switching Why we don’t use circuit switching to connect two computers –Used since early days of telephone –Dedicated connection is formed between two points –Connection remains active for duration of transmission –Important when order of receiving information is critical Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall10

12. Data Transmission and Protocols Circuit Switching (cont.) Why we don’t use circuit switching to connect two computers (cont.) –Inefficient when applied to computers –Computers transmits data in a group, or burst –Processor works on next task and ceases to communicate until ready to transmit next burst –Would need to keep circuit open, therefore unavailable or have to be reestablished for each burst Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall11

13. Data Transmission and Protocols Packet Switching What computers use to communicate –Packet switching makes computer communication efficient –Doesn’t require a dedicated communications circuit –Data is broken into smaller chunks (packets or data packets) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall12

14. Data Transmission and Protocols Packet Switching (cont.) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall13

15. Data Transmission and Protocols Packet Switching (cont.) What computers use to communicate (cont.) –Packets are sent over various routes at same time –They are reassembled at the destination by receiving computer –Fulfilled original goal of Internet: Data can still travel to destination if a node is disabled or destroyed Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall14

16. Data Transmission and Protocols Packet Switching (cont.) What information a packet contains 1.An address to which the packet is being sent 2.The address from where the packet originates 3.Reassembly instructions, if the original data is split between packets, and 4.The data that’s being transmitted Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall15

17. Animation of packet switching…. –http://en.wikipedia.org/wiki/Packet_switchinghttp://en.wikipedia.org/wiki/Packet_switching TCP/IP data packet structure –http://www.thegeekstuff.com/2012/03/ip-protocol-header/http://www.thegeekstuff.com/2012/03/ip-protocol-header/ https://www.youtube.com/watch?v=3mQK8uyKrFU Network Switches & routers –https://www.youtube.com/watch?v=Ofjsh_E4HFY Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall16

18. Review of terms –Proxy server - a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server and the proxy server evaluates the request as a way to simplify and control its complexity. Proxies were invented to add structure and encapsulation to distributed systems. [serverclients [ –Network Switch - a computer networking device that connects devices together on a computer network, by using a form of packet switching to forward data to the destination device.computer networking device computer networkpacket switching –Router - a networking device, commonly specialized hardware, that forwards data packets between computer networks. This creates an overlay internetwork, as a router is connected to two or more data lines from different networks. When a data packet comes in one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. A data packet is typically forwarded from one router to another through the networks that constitute the internetwork until it reaches its destination node. [1data packetscomputer networksinternetworkrouting tablerouting policy Internet [1 Copyright © 2013 Pearson Education, Inc. Publishing as Prentice Hall17

19. Data Transmission and Protocols Packet Switching (cont.) Why packets take different routes, and how do they decide which route to use –Routers monitor traffic and decide most effective route –Windows utility tracert shows details of exact route request takes to destination server Tracert google.com and www.cityoflondon.gov.uk Ping google.com Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall18

20. Data Transmission and Protocols TCP/IP What protocol the Internet uses for transmitting data –Main suite of protocols is TCP/IP Transmission Control Protocol (TCP) Internet Protocol (IP) –Consists of many interrelated protocols Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall19

21. Data Transmission and Protocols TCP/IP (cont.) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall20

22. Internet Identity: IP Addresses and Domain Names Each computer, server, or device connected to the Internet is required to have a unique number IP address is the unique number Humans remember words better than numbers Domain names are word-based IP addresses Copyright © 2014Pearson Education, Inc. Publishing as Prentice Hall21

23. Internet Identity: IP Addresses and Domain Names IP Addresses IP address –A unique identification number that defines each device connected to the Internet –Fulfills same function as a street address –Must be registered with the Internet Corporation for Assigned Names and Numbers (ICANN) Ensures their uniqueness Allocates to network administrators Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall22

24. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) What an IP address looks like –Typical IP address: 197.169.73.63 –Referred to as a dotted decimal number (dotted quad) –Binary form is 11000101.10101001.01001001.00111111 –Each is referred to as an octet Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall23

25. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) What an IP address looks like –IP addresses are considered 32-bit numbers –Can represent 4,294,967,296 values Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall24

26. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) Limited number of IP addresses –Internet Protocol version 4 (IPv4) was created in 1981 before explosive growth of Internet –IPv4 offers a fixed number of IP addresses Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall25

27. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) Other Internet addressing systems –Internet Protocol version 6 (IPv6), developed by IETF, uses 128-bit addressing instead of 32-bit Internet Engineering Task Force (IETF) https://www.ietf.org/ Internet Engineering Task Force –XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX Each X is a hexadecimal digit Hexadecimal is base-16 number system Uses 0-9 or A-F Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall26

28. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) Other Internet addressing systems (cont.) –IPv6 provides virtually unlimited supply of IP addresses –All modern operating systems handle both IPv4 and IPv6 –Majority of routing still uses IPv4 –IPv6 conversion will happen soon as IPv4 addresses are running out Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall27

29. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) How my computer gets an IP address (either/or) –Static IP address never changes Assigned by network administrator or ISP –Dynamic IP address is temporary Assigned from a pool of addresses More common Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall28

30. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) How dynamic addresses are assigned –Handled by Dynamic Host Configuration Protocol (DHCP) –Belongs to TCP/IP protocol suite –Takes from pool of available addresses on as- needed basis –Assigns address for duration of session –Might not be the same from session to session Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall29

31. Internet Identity: IP Addresses and Domain Names IP Addresses (cont.) Benefits of dynamic addressing –Provides a more secure environment –Helps to keep hackers out of system Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall30

32. Internet Identity: IP Addresses and Domain Names Domain Names Why IP addresses are not seen –Domain names take the place of IP address –Makes it easier for people to remember Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall31

33. Internet Identity: IP Addresses and Domain Names Domain Names (cont.) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall32 How my computer knows the IP address of another computer Computer converts URL to an IP address by consulting a database on a domain name system (DNS) server Functions like a phone book for the Internet

34. Internet Identity: IP Addresses and Domain Names Domain Names (cont.) Controlling domain name registration –ICANN assigns companies or organizations to manage registration –One company is assigned each TLD –Maintains a database of all registered domains and contact information –. VeriSign is the current ICANN-accredited domain name registrar for the.com and.net domains. VeriSign provides a database that lists all the registered.com and.net domains and their contact information. You can look up any.com or.net domain at Network Solutions (networksolutions.com) to see whether it’s registered and, if so, who owns it. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall33

35. Internet Identity: IP Addresses and Domain Names Domain Names (cont.) How domains are organized –Organized by level –Portion after the dot is the top-level domain (TLD) –Establish by ICANN ICANN https://www.icann.org/ The Internet Corporation for Assigned Names and Numbers (ICANN) –Within TLDs are many second-level domains Needs to be unique within its TLD Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall34

36. Internet Identity: IP Addresses and Domain Names Domain Names (cont.) Controlling domain name registration (cont.) –Country-specific domains are controlled by groups in those countries –Complete list of TLDs are found on Internet Assigned Numbers Authority site (iana.org) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall35

37. HTML, XML, and other web Building Blocks HTML How web pages are formatted –Hypertext Markup Language (HTML) Not a programming language Set of rules for marking blocks of text Browser knows how to display them Surrounded by pairs of HTML tags Tags and text are referred to as an element This should be bolded and italicized. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall36

38. Viewing the HTML coding of a web page –HTML documents are text documents with tags applied –Right-click, then select View Source Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall37 HTML, XML, and other web Building Blocks HTML (cont.)

39. Current HTML standard –HTML5 is current version; should be finalized by 2014 –Modernizes features, such as Reducing need for external plug-ins (like Flash) Supporting better error handling Introducing new tags to support media, like and Making it easier to draw graphics Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall38 HTML, XML, and other web Building Blocks HTML (cont.)

40. How developers can easily change the formatting of HTML elements –Cascading style sheet List of rules that define in one location how to display HTML elements Enable a web browser to define formatting for each element Acts as a template Allows global changes to be done easily Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall39 HTML, XML, and other web Building Blocks HTML (cont.)

41. Where the cascading comes in –Different layers of styles External: Stored in a separate file Embedded: Stored in the current document Inline: Stored in a single line in the document –Different rules can be created for the same type of element in different places Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall40 HTML, XML, and other web Building Blocks HTML (cont.)

42. Where the cascading comes in –Style sheets are merged –If conflict in rules, then rules are weighted in hierarchy (cascade) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall41 HTML, XML, and other web Building Blocks HTML (cont.)

43. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall42 HTML, XML, and other web Building Blocks HTML (cont.)

44. How XML is different from HTML –eXtensible Markup Language (XML) describes what data is described rather than how it is to be displayed –Users build own markup languages to accommodate data formats and needs –Provides method of data validation through XML schema diagrams (XSD) Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall43 HTML, XML, and other web Building Blocks XML

45. Custom XML packages –XML has spawned custom packages for specific communities –Goal is information exchange standards that can be easily constructed and customized to serve growing variety of online applications Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall44 HTML, XML, and other web Building Blocks XML (cont.)

46. Internet protocol a browser uses to send requests –Hypertext Transfer Protocol (HTTP) was created for the transfer of hypertext documents –Hypertext documents have text that is linked to other documents or media Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall45 HTML, XML, and other web Building Blocks Web Browser Protocols

47. How a browser safeguards secure information –Hypertext Transfer Protocol Secure (HTTPS) ensures data security –Combination of HTTP and Secure Sockets Layer (SSL), a network security protocol Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall46 HTML, XML, and other web Building Blocks Web Browser Protocols (cont.)

48. How a browser safeguards secure information (cont.) –Transport Layer Security (TLS) is an updated extension of SSL –These provide data integrity and security for transmissions over the Internet Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall47 HTML, XML, and other web Building Blocks Web Browser Protocols (cont.)

49. HTML, XML, and other web Building Blocks Server-Side Applications Server-side applications –Web is a client/server network –Program on server is considered server-side –Can require many communication sessions between client and server –Can perform very complex operations Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall48

50. Popular server-side programming choices –CGI (Common Gateway Interface) –ASP.NET (Active Server Pages) –VBScript –PerlScript Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall49 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

51. How CGI makes a web page more interactive –Most browser requests result in file being displayed in browser –Some programs can perform actions, such as gathering a name and address and adding it to a database Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall50 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

52. How CGI makes a web page more interactive (cont.) –Common Gateway Interface (CGI) provides methodology that allows a browser to request that a program file be executed –Allows functionality beyond simple display of information Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall51 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

53. Programming language used to create a CGI program –Can be created in almost any language –Known as CGI scripts –Common languages include Perl C C++ Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall52 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

54. Programming language used to create a CGI program (cont.) –Almost any task can be accomplished through a CGI script Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall53 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

55. How CGI programs are executed –CGI bin (directory) is created and all CGI scripts go into this directory –These files aren’t just read and sent, they need to be run Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall54 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

56. How CGI programs are executed (cont.) –Example Step 1: A button gives a message Step 2: Clicking the button executes a script Step 3: Script generates a form Step 4: Form information is sent back to server and recorded in database Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall55 HTML, XML, and other web Building Blocks Server-Side Applications (cont.)

57. HTML, XML, and other web Building Blocks Client-Side Applications Client-side applications –Program that runs on client computer –Requires no interaction with web server –New data is only sent in response to a request –Exchange of data can make interactivity inefficient and slow –More efficient to run client-side programs on local computer Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall56

58. How client-side programming is done –HTML embedded scripting language tucks programming code directly in HTML tag Most popular is JavaScript –Applet (small application) is downloaded to client and runs when needed Most common language is Java Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall57 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

59. Delay in downloading an applet –There is some delay but once downloaded it executes without further communication with server –Example Step 1: Browser makes request Step 2: Server returns Java applet Step 3: Computer executes the code Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall58 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

60. Scripting technologies –Dynamic HTML (DHTML) combines HTML, cascading style sheets, and JavaScript –Creates lively and interactive websites –Allows a web page to change after it’s been loaded Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall59 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

61. Scripting technologies –Occurs in response to user actions –Brings special effects without downloading and installing plug-ins or special software Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall60 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

62. JavaScript –Commonly used scripting language –Creates DHTML effects –Not the same as Java programming language –Allows HTML documents to respond to mouse clicks and typing –All actions are executed on the client computer –Keeps web pages from being lifeless Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall61 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

63. How JavaScript controls the components of a web page –Document Object Model (DOM) is used to organize objects and page elements –Defines every item on a web page as an object –Allows web developers to easily change the look and feel of objects Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall62 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

64. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall63 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

65. Where web programming is headed –Web pages interacting with servers at times other than when being fetched –Ongoing exchange of information –Updating information without page refresh or leaving the page –AJAX (Asynchronous JavaScript and XML) facilitates these applications Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall64 HTML, XML, and other web Building Blocks Client-Side Applications (cont.)

66. Communications Over the Internet E-Mail Invention of e-mail –Ray Tomlinson (1971) helped develop ARPANET (precursor to the Internet) –Written to enable users to leave text messages for each other on a single machine –Extended to sending text messages between machines on Internet –Became the most popular application –1973: Accounted for 75% of all data traffic Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall65

67. How e-mail travels the Internet –Simple Mail Transfer Protocol (SMTP) sends e-mails along the Internet –Part of the Internet Protocol suite –Client/server application –Passes through several e-mail servers Specialized computers whose sole function is to store, process, and send e-mail Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall66 Communications Over the Internet E-Mail (cont.)

68. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall67 Communications Over the Internet E-Mail (cont.)

69. Where e-mail servers are located –ISPs have e-mail servers that use SMTP Step 1: Your ISP’s e-mail server receives your e-mail Step 2: E-mail server reads domain name and determines location using a DNS server Step 3: DNS server turns domain name into IP address Step 4: E-mail is forwarded to receiver’s ISP server Step 5: E-mail is stored on receiver’s e-mail server Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall68 Communications Over the Internet E-Mail (cont.)

70. How we are able to send files as attachments –SMTP handles text messages –Multipurpose Internet Mail Extensions (MIME) specification created to send files –E-mail is sent as text, but MIME handles the encoding and decoding of files Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall69 Communications Over the Internet E-Mail (cont.)

71. Communications Over the Internet E-Mail Security: Encryption How other people can read my e-mail –Highly susceptible to being read because sent in plain text –Copies might exist on numerous servers –Encryption helps protect sensitive messages Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall70

72. How to encrypt e-mail –Many e-mail servers offer built-in encryption Hushmail Comodo SecureEmail –Can sign up to experiment –Use secure account when secure communications are required Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall71 Communications Over the Internet E-Mail Security: Encryption (cont.)

73. How encryption works –Codes e-mail so that only person with key to code can decode the message –Private key –Public key Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall72 Communications Over the Internet E-Mail Security: Encryption (cont.)

74. Private key encryption –Only the two parties have the code –Could be a shift code –Could be more complex substitution code –Main problem is key security, code is broken if: Code is stolen Someone is savvy about decoding Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall73 Communications Over the Internet E-Mail Security: Encryption (cont.)

75. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall74 Communications Over the Internet E-Mail Security: Encryption (cont.)

76. Public key encryption –Two keys (key pair) are created One for coding, one for decoding –Coding key is distributed as public key Message being sent to you is coded using public key –Decode using private key Only receiver knows private key –Mathematical relationship between the two keys Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall75 Communications Over the Internet E-Mail Security: Encryption (cont.)

77. Encryption used on the Internet –Public key is the most common –Pretty Good Privacy (PGP) is available for download –Can generate key pairs to provide private key if desired Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall76 Communications Over the Internet E-Mail Security: Encryption (cont.)

78. What a key looks like –Binary numbers –Vary in length depending on security needs –Key and message run through complex algorithm converts text into unrecognizable code –Each key generates different code Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall77 Communications Over the Internet E-Mail Security: Encryption (cont.)

79. Private key’s level of security –Impossible to deduce private key from public key because of complexity of algorithms used –In brute force attack every possible combination is tried –Can enable hackers to deduce key and decode message Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall78 Communications Over the Internet E-Mail Security: Encryption (cont.)

80. Safe key –1990s: 40-bit keys thought to be completely resistant to brute force attacks –1995: French programmer broke 40-bit key –128-bit keys became standard –Strong encryption calls for 256-bit keys Could take hundreds of billions of years to crack Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall79 Communications Over the Internet E-Mail Security: Encryption (cont.)

81. Encryption used in corporations –Paid services include Confirmation of message delivery Message tracking Overwriting of e-mail messages when deleted –Securus Systems and ZixCorp provide these services Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall80 Communications Over the Internet E-Mail Security: Encryption (cont.)

82. Communications Over the Internet Instant Messaging What you need to run instant messaging –Client program that connects to an instant messaging (IM) service –Examples Yahoo! Messenger GoogleTalk Windows Live Messenger Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall81

83. How instant messaging works –Client software makes a connection with chat server –Provides connection information to your device –Because friend’s device and your device have same connection information, server isn’t involved in chat session –Chatting takes place directly between two devices over the Internet Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall82 Communications Over the Internet Instant Messaging (cont.)

84. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall83 Communications Over the Internet Instant Messaging (cont.)

85. IM security –Most do not use high level of security –Vulnerable to Viruses Worms Hacking threats Eavesdropping –Increased security is in development –Employers can monitor IM sessions Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall84 Communications Over the Internet Instant Messaging (cont.)

86. 1. Who owns, manages, and pays for the Internet? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall85 Chapter 13 Summary Questions

87. 2. How do the Internet’s networking components interact? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall86 Chapter 13 Summary Questions

88. 3. What data transmissions and protocols does the Internet use? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall87 Chapter 13 Summary Questions

89. 4. Why are IP addresses and domain names important for Internet communications? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall88 Chapter 13 Summary Questions

90. 5. What web technologies are used to develop web applications? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall89 Chapter 13 Summary Questions

91. 6. How do e-mail and instant messaging work, and how is information using these technologies kept secure? Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall90 Chapter 13 Summary Questions

92. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of the publisher. Printed in the United States of America. Copyright © 2014 Pearson Education, Inc. Copyright © 2014 Pearson Education, Inc. Publishing as Prentice Hall