1. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 1 Chapter 6 Data Communications

2. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 2

3. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 3 Agenda 1.What is a computer network? 2.What are the components of a LAN? 3.What are the alternatives for a WAN? 4.How does encryption work? 5.What is the purpose of a firewall? 6.What is a VPN and why is it important?

4. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 4 What Is a Computer Network? Network Collection of computers Communicate with one another over transmission line Three basic types Local area network (LAN) Wide area network (WAN) Internet

5. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 5 Major Network Types

6. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 6 LAN Connects computers residing in single location 2 to several hundred computers One geographic area Communication lines can be placed where the organization wants

7. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 7 Different Network Topologies-Video Bus Topology Star Topology Ring Toplogy

8. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 8 WAN Connect computers in different geographical areas Two or more cities Uses communication networks from vendors Licensed by government

9. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 9 Internet Network of networks Connect LANs, WANs, and other internets Private networks of networks Use a variety of communication methods and conventions Seamless flow of data provided by layered protocol Set of rules that communicating devices follow, ex: TCP( Transmission Control Protocol )/IP( Internet Protocol )

10. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 10 What’s a protocol? a human protocol and a computer network protocol: Hi Got the time? 2:00 TCP connection request TCP connection response Get http://www.stfx.ca time

11. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 11 What Are the Components of a LAN? Local area network Computers connected on single company site Usually located within half mile area Property controlled by company operating network Company can run cabling as necessary Components Switch Special purpose computer that receives and transmits messages Network interface card (NIC) or Ethernet card Hardware that connects each device’s circuitry to the cable Onboard NIC or card that fits into an expansion slot

12. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 12 Lan Usually located within half mile area

13. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 13 NIC Devices Media connections Unshielded twisted pair (UTP) cable RJ-45 connector Optical fiber cables Light rays reflected inside glass core surrounded by cladding

14. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 14 Network Interface Card

15. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 15 Unshielded Twisted Pair

16. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 16 Optical Fiber Cable

17. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 17 IEEE 802.3 Protocol Ethernet protocol standard Specifies hardware characteristics Describes how messages are packages Determines how messages are processed

18. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 18 LANs with Wireless Connections Wireless NIC (WNIC) LAN operation NICs operate on 802.3 protocol WNICs operate on 802.11 protocol WNICs connect to access point (AP) AP processes both standards

19. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 19 Wireless LAN

20. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 20

21. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 21 What Are the Alternatives for a WAN? WANs connect computers at separate sites No cabling between sites Cable connections made through licensed communications companies Internet service provider (ISP) Provides legitimate Internet address Serves as gateway to Internet Pay for Internet

22. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 22 Internet network architecture

23. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 23 A Simple Internet Connection

24. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 24 Connecting to the ISP Connections made through: Regular telephone lines Use of DSL line Cable TV lines All require digital data to be converted to analog Modem makes conversion

25. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 25 Analog to Digital method

26. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 26 Dial-Up Modems Handles conversion between analog and digital Connection made by dialing ISP Maximum transmission speed of 56 kbps PPP ( point-to point protocol) controls message packaging and handling

27. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 27 DSL ( digital subscriber line) Modems Operates over telephone lines Do not interfere with voice telephone service Faster data transmission than dial-up Connection always maintained Download and upload speeds vary Asymmetric digital subscriber lines (ADSL) Symmetrical digital subscriber lines (SDSL)

28. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 28 Cable Modems Provide high-speed data transmission Use cable television lines High-capacity optical fiber cable run to neighborhood distribution center Television cables connect at distribution center and runs to subscribers Does not interfere with television transmission Up to 500 subscribers connected at each center Performance varies based on number connected

29. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 29 Cable Modems, continued Download speed up to 15 Mbps, upload up to 256 kbps Speeds Narrowband Transmission speeds less then 56 kbps Broadband Transmission speeds in excess of 256 kbps

30. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 30 Networks of Leased Lines WAN connects computers located at geographically distributed sites Access devices connect sites to transmission Switch Router (moves network traffic from one node to another on a network) Alternative is leasing lines T1, T3 Set up as a point-to-point line Only predefined sites can use leased lines Provide low cost per bit transmitted

31. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 31 Wan Using Leased Lines

32. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 32 Transmission Line Types, Uses, and Speeds Figure 6-11

33. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 33 Criteria for Comparing WANs Costs Setup costs Examples: costs of acquiring lines and equipment Operational costs Examples: lease fees, ISP charges, training Maintenance costs Examples: periodic maintenance, repair, upgrades Performance Speed Latency Availability Loss rate Transparency Performance guarantees Growth potential Length of contract commitment

34. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 34

35. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 35 Contemporary Security Challenges and Vulnerabilities

36. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 36 Worldwide Damage from Digital Attacks

37. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 37 Security Guide: How Does Encryption Work? Encryption Process of transforming clear text into coded text Used for secure storage or communication Uses algorithms Key Used to encrypt data Algorithm applies key to produce coded message Symmetric encryption ( same key is used for encoding and decoding) Asymmetric encryption ( different keys are used)

38. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 38 Security Guide: How Does Encryption Work?, continued Public key/private key Public key used to encrypt messages Public key sent to other party to encode messages to be sent back Decoded with private key Complex and slow HTTPS [Secure Hypertext Transfer Protocol] used for encrypting data flowing over the Internet Encodes messages using Web site’s public key, decoded with private key

39. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 39 video How an encryption works video

40. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 40 Public/Private Key A big random number is used to make a public-key/private-key pair.

41. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 41 Public/Private keys Anyone can encrypt using the public key, but only the holder of the private key can decrypt. Secrecy depends on the secrecy of the private key.

42. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 42 Using a private key to encrypt (thus signing) a message; anyone can check the signature using the public key. Validity depends on private key security.

43. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 43 By combining your own private key with the other user's public key, you can calculate a shared secret that only the two of you know.shared secret

44. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 44 Steganography Steganography is the hiding of information in innocent looking objects and is a part of cryptography. Steganos means hidden and graffein write. Since the arrival of digital files for image and sound, steganography has gained popularity. Steganography

45. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 45 What Is the Purpose of a Firewall? Computer device that prevents unauthorized network access May be special-purpose computer or program Organizations may have multiple firewalls Perimeter firewalls sit outside organizational network Internal firewalls are inside network Packet-filtering firewalls examine source address, destination address, and other data before allowing message to pass May filter both incoming and outgoing messages Access control list (ACL) encodes rules stating what packets are allowed or prohibited

46. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 46 Multiple Firewalls

47. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 47 A Corporate Firewall

48. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 48 Wireless Security

49. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 49 Wireless security video

50. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 50 What Is a VPN and Why Are VPNs Important? Virtual private network (e.g.StFX vpn) Another WAN alternative Uses Internet or private network to create appearance of point-to-point connections Uses public Internet to create appearance of private network Client and server have point-to-point connection called tunnel Private pathway over shared network Secure, encrypted communications

51. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 51 Remote access using VPN

52. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 52 WAN using VPN

53. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 53 STFX VPN http://www.stfx.ca/tsg/networkservices/studentn etworkservices.php

54. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 54 How RFID (Radio-Frequency Identification) Works RFID uses low-powered radio transmitters to read data stored in a tag at distances ranging from 1 inch to 100 feet. The reader captures the data from the tag and sends them over a network to a host computer for processing.

55. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 55 An RFID Tag – used by Wal-Mart

56. © 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke Slide 56 RFID Video 1 RFID Video RFID Video 2 RFID Video 3