Chapter 6       Data Communications© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
What Is a Computer Network?       Network        is a collection of hardware components and          computers interconn...
LAN       Connects computers residing in single       location         2 to several hundred computers         One geogr...
WAN       Connect computers in different        geographical areas         Two or more cities       Uses communication ...
Internet      • The Internet is a global system of          interconnected computer networks that use the          standar...
LAN VS WAN                        LAN                           WANData                                    Experiences mor...
LAN vs WANspeed:           high speed(1000mbps) less speed(150mbps)                 Because it covers a        Maintaining...
LAN vs WAN            Have a small geographical Have a large geographical rangeGeographica range and do not need     gener...
LAN vs WANs            LAN (Local Area           WAN (Wide Area Network) is a            Network) is a computer computer n...
What Are the Components of a       LAN?         Local area network           Computers connected on single company      ...
Switches
NIC Devices        MAC address          Unique identifier        Media connections          Unshielded twisted pair (U...
NIC card
IEEE 802.3 Protocol        Ethernet protocol standard          Specifies hardware characteristics          Describes ho...
LANs with Wireless Connections        Wireless NIC (WNIC)        LAN operation          NICs operate on 802.3 protocol ...
What Are the Alternatives for a WAN?        WANs connect computers at separate sites          No cabling between sites  ...
Connecting to the ISP        Connections made through:          Regular telephone lines          Use of DSL line       ...
MIS In Use: Larry Jones (Student)       Network Services        Larry set up LAN networks        Realized that he had to...
Dial-Up Modems        Handles conversion between analog and digital        Connection made by dialing ISP        Maximu...
DSL Modems        Operates over telephone lines        Do not interfere with voice telephone service        Faster data...
Cable Modems        Provide high-speed data transmission        Use cable television lines          High-capacity optic...
Cable Modems, continued        Download speed up to 10Mbps, upload up to 256         kbps        Operate with Layer 1 an...
Networks of Leased Lines        WAN connects computers located at geographically         distributed sites        Access...
Transmission Line Types, Uses, and       Speeds          Figure 6-116-24
Public Switched Data Network       (PSDN)        Network of computers and leased lines          Developed and maintained...
PSDN Protocols        Frame relay          Process traffic at 56 kbps to 40 Mbps          Simplest and easiest to suppo...
Criteria for Comparing WANs        Costs         Setup costs           Examples: costs of acquiring lines and equipment...
Criteria for Comparing WANs,       continued        Performance          Speed          Latency (measure of time delay)...
Security Guide: How Does       Encryption Work?        Encryption          Process of transforming clear text into coded...
Security Guide: How Does       Encryption Work?, continued        Public key/private key          Public key used to enc...
What Is the Purpose of a       Firewall?        Computer device that prevents unauthorized network         access       ...
What Is a VPN and Why Are VPNs       Important?        Virtual private network          Uses Internet or private network...
How Does the Knowledge in This       Chapter Help Dee?        Dee and salespeople use thin client computers          Dee...
How Does the Knowledge in This       Chapter Help Dee?, continued        IT department cannot schedule resources to setup...
How Does the Knowledge in This       Chapter Help Dee?, continued        Dee negotiates with IT department          Thre...
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Chapter 6 mis

  1. 1. Chapter 6 Data Communications© 2008 Pearson Prentice Hall, Experiencing MIS, David Kroenke
  2. 2. What Is a Computer Network?  Network  is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information  Collection of computers  Communicate with one another over transmission line  Three basic types  Local area network (LAN)  Wide area network (WAN)6-2  Internet
  3. 3. LAN  Connects computers residing in single location  2 to several hundred computers  One geographic area  Communication lines can be placed where the organization wants6-3
  4. 4. WAN  Connect computers in different geographical areas  Two or more cities  Uses communication networks from vendors  Licensed by government6-4
  5. 5. Internet • The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite (TCP/IP) to serve billions of users worldwide • 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 follow6-5
  6. 6. LAN VS WAN LAN WANData Experiences more data Experiences fewer datatransmission transmission errors as transmission errorsError: compared to LAN WANs have a lower dataData transfer LANs have a high data transfer rate as compared torates: transfer rate LANs Computers connected to a one LAN can be wide-area network are often connected to other LANs connected through publicConnection: over any distance via networks, such as the telephone lines and radio telephone system. They can waves also be connected through leased lines or satellites
  7. 7. LAN vs WANspeed: high speed(1000mbps) less speed(150mbps) Because it covers a Maintaining WAN is relatively small difficult because of itsMaintenance geographical area, LAN wider geographicalcosts: is easier to maintain at coverage and higher relatively low costs. maintenance costs. LANs tend to have less WANs tend to be less fault problems associated tolerant. as it consists of aFault Tolerance: with them, as there are large amount of systems a smaller amount of there is a lower amount of systems to deal with. fault tolerance. Network in an Internet is the bestExample: organization can be a example of a WAN LAN
  8. 8. LAN vs WAN Have a small geographical Have a large geographical rangeGeographica range and do not need generally spreading acrossl spread: any leased boundaries and need leased telecommunication lines telecommunication lines If there is a need to set-up In this case since networks in a couple of extra devices remote areas have to beSet-up costs: on the network, it is not connected hence the set-up very expensive to do that costs are higher WANs (like the Internet) are not Typically owned, owned by any one organization controlled, and managed but rather exist under collectiveOwnership: by a single person or or distributed ownership and organization management over long distances
  9. 9. LAN vs WANs LAN (Local Area WAN (Wide Area Network) is a Network) is a computer computer network that covers a network covering a small broad area (e.g., any networkDefinition: geographic area, like a whose communications links cross home, office, schools, or metropolitan, regional, or national group of buildings. boundaries over a long distance layer 2 devices like Layers 3 devices Routers, Multi-Compone switches, bridges. layer1 layer Switches and Technologynts: devices like hubs , specific devices like ATM or Frame- repeaters relay Switches etc
  10. 10. 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)  Hardware that connects each device’s circuitry to6-10 the cable
  11. 11. Switches
  12. 12. NIC Devices  MAC address  Unique identifier  Media connections  Unshielded twisted pair (UTP) cable  RJ-45 connector  Optical fiber cables  Light rays reflected inside glass core surrounded by cladding  Uses ST and SC connectors6-12
  13. 13. NIC card
  14. 14. IEEE 802.3 Protocol  Ethernet protocol standard  Specifies hardware characteristics  Describes how messages are packages  Determines how messages are processed  Operates at Layers 1 and 2 of TCP/IP-OSI architecture(physical layer and data link layer)  Personal computers usually support 10/100/1000 (bandwidth) Ethernet6-14
  15. 15. 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 standards6-15
  16. 16. 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 Internet6-16
  17. 17. 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 conversion6-17
  18. 18. MIS In Use: Larry Jones (Student) Network Services  Larry set up LAN networks  Realized that he had to offer support  Customers had problems  Customers needed to add more devices  Coupled installation with support package  Extra charges for support beyond normal wear and tear6-18
  19. 19. Dial-Up Modems  Handles conversion between analog and digital  Connection made by dialing ISP  Maximum transmission speed of 56kbps  Modulation governed by V.34, V.90. or V.92 standards  PPP controls message packaging and handling6-19
  20. 20. DSL Modems  Operates over telephone lines  Do not interfere with voice telephone service  Faster data transmission than dial-up  Connection always maintained  Use their own Layer 1 and 2 protocols  Download and upload speeds vary  Asymmetric digital subscriber lines (ADSL)  Symmetrical digital subscriber lines (SDSL)6-20
  21. 21. 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 connected6-21
  22. 22. Cable Modems, continued  Download speed up to 10Mbps, upload up to 256 kbps  Operate with Layer 1 and 2 protocols  Speeds  Narrowband  Transmission speeds less then 56 kbps  Broadband  Transmission speeds in excess of 256 kbps6-22
  23. 23. Networks of Leased Lines  WAN connects computers located at geographically distributed sites  Access devices connect sites to transmission  Switch  Router  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 transmitted6-23
  24. 24. Transmission Line Types, Uses, and Speeds Figure 6-116-24
  25. 25. Public Switched Data Network (PSDN)  Network of computers and leased lines  Developed and maintained by vendor  Time leased on network  Utility that supplies network for other companies to lease  Each site leases line to connect to PSDN network at access point  Point of presence (POP)  Saves setup and maintenance activities6-25
  26. 26. PSDN Protocols  Frame relay  Process traffic at 56 kbps to 40 Mbps  Simplest and easiest to support  Asynchronous transfer mode (ATM)  Process speeds from 1 to 156 Mbps  Ethernet  Operates at speeds of 10 to 40 Gpbs6-26
  27. 27. 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, upgrades6-27
  28. 28. Criteria for Comparing WANs, continued  Performance  Speed  Latency (measure of time delay)  Availability  Loss rate  Transparency  Performance guarantees  Growth potential  Length of contract commitment6-28
  29. 29. 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  Asymmetric encryption6-29
  30. 30. 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 communication over Internet  Encrypted using SSL/TLS protocol  Encodes messages using Web site’s public key, decoded with private key6-30
  31. 31. 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 prohibited6-31
  32. 32. What Is a VPN and Why Are VPNs Important?  Virtual private network  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 communications6-32
  33. 33. How Does the Knowledge in This Chapter Help Dee?  Dee and salespeople use thin client computers  Dee creates blog entries on Web pages using Moveable Type  Salespeople use pages served by Moveable Type  Client computers contain VPN client software  Interacts with VPN server via Internet  Secure, private connections  Firewalls stop traffic not addressed to VPN server  Salespeople know how to use VPN6-33
  34. 34. How Does the Knowledge in This Chapter Help Dee?, continued  IT department cannot schedule resources to setup blog server in timely fashion  Will not allow outside person to do setup  Would then have access to system  Consultant can create server on unprotected test server  Can be copied onto network server after acceptance  Requires some internal IT labor  Consultant could include Trojan horse virus or malware  Install only software from known sources  Code should not reside on production server6-34
  35. 35. How Does the Knowledge in This Chapter Help Dee?, continued  Dee negotiates with IT department  Threatens to set up own system of user Ids and passwords  Says she will set up blog on public server  Would cause confusion that would add to IT department’s work  Her proposal is the lesser of two evils6-35

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