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    1. 1. Chapter 10 <ul><li>Data Communications </li></ul>MANAGEMENT INFORMATION SYSTEMS 8/E Raymond McLeod, Jr. and George Schell Copyright 2001 Prentice-Hall, Inc. 10-
    2. 2. Communication Basics <ul><li>Computer communications is at three levels </li></ul><ul><ul><li>Application level </li></ul></ul><ul><ul><li>Computer level </li></ul></ul><ul><ul><li>Communication channel </li></ul></ul><ul><li>Protocol </li></ul><ul><ul><li>Set of rules for communications </li></ul></ul><ul><ul><li>OSI Standard </li></ul></ul>10-
    3. 3. OSI Reference Model Layer Name Purpose 7 Application Layer Application-to-application communication 6 Presentation Layer Manage data representation conversions 5 Session Layer Establish and maintain communication channel 4 Transport Layer Guarantee end-to-end integrity of transmission 3 Network Layer Route data between network addresses 2 Data Link Layer Move data from one network address to another 1 Physical Layer Put data onto and off of the network media 10-
    4. 4. ISO Website 10-
    5. 5. Protocols for Computer Communication <ul><li>Early computers </li></ul><ul><ul><li>Terminals </li></ul></ul><ul><ul><li>Sneaker net </li></ul></ul><ul><li>System Network Architecture (SNA) </li></ul><ul><ul><li>Established by IBM in 1974 </li></ul></ul><ul><ul><li>Proprietary </li></ul></ul><ul><li>Token-Ring </li></ul><ul><ul><li>Host computer controlled </li></ul></ul><ul><ul><li>peer-to-peer </li></ul></ul>10-
    6. 6. Protocols for Computer Communication <ul><li>Ethernet </li></ul><ul><ul><li>Xerox working with Intel and Digital Equipment Corporation developed this protocol </li></ul></ul><ul><ul><li>Non-proprietary </li></ul></ul><ul><ul><li>Defined by IEEE </li></ul></ul><ul><ul><li>Works on a single transmission line </li></ul></ul><ul><ul><li>No token is passed </li></ul></ul>10-
    7. 7. Packets <ul><li>Piece of the total data to be communicated, combined with the address of the destination computer for the data and other control information. </li></ul>Transmission Control Protocol/Internet Protocol (TCP/IP) is one of the more important packet switching protocols 10-
    8. 8. Network Addresses <ul><li>Address </li></ul><ul><ul><li>Four-part set of numbers </li></ul></ul><ul><ul><li>Each from 0 to 255 </li></ul></ul><ul><li>Internet Service Providers (ISPs) </li></ul><ul><ul><li>User connects through common carrier </li></ul></ul><ul><li>Serial Line Internet Protocol (SLIP) and Point-to-Point Protocol (PPP) </li></ul><ul><ul><li>Protocols for users at home </li></ul></ul>10-
    9. 9. Protocols for Public Phone Systems <ul><li>X.25 </li></ul><ul><ul><li>analog </li></ul></ul><ul><ul><li>older protocol </li></ul></ul><ul><li>Integrated Services Digital Network (ISDN) </li></ul><ul><ul><li>Digital </li></ul></ul><ul><ul><li>Can carry voice, data, and video </li></ul></ul>10-
    10. 10. Protocols for Public Phone Systems (cont.) <ul><li>Frame Relays </li></ul><ul><ul><li>Move to fiber optics </li></ul></ul><ul><li>Asynchronous Transfer Mode (ATM) </li></ul><ul><ul><li>Smaller packet size </li></ul></ul><ul><ul><li>Faster transmission speeds </li></ul></ul>10-
    11. 11. Data Communications Links the General Systems Model Elements Standards Management Information processor Environment Input Transformation Output 10-
    12. 12. Networks <ul><li>Each device must be connected to the communications medium via a network interface card (NIC) </li></ul>10-
    13. 13. Types of Networks <ul><li>LAN (local area network) </li></ul><ul><ul><li>Limited area but could include 100 or so micros </li></ul></ul><ul><ul><li>Facilitates office automation </li></ul></ul><ul><li>MAN (metropolitan area networks) </li></ul><ul><ul><li>spans one city/metropolitan area </li></ul></ul><ul><li>WAN (wide area network) </li></ul><ul><ul><li>Covers a large geographic area </li></ul></ul><ul><ul><li>Includes a wide variety of circuits </li></ul></ul><ul><ul><li>Usually includes host computers </li></ul></ul>10-
    14. 14. Users Manager 1 Secretary 1 Secretary 2 Workstation 1 Workstation 2 Workstation 3 Workstation 4 Manager 2 Network Server Hard Disk Letter Quality Printer Plotter A Local Area Network 10-
    15. 15. Common LAN Topologies Star 10-
    16. 16. Common LAN Topologies Ring 10-
    17. 17. Common LAN Topologies Bus 10-
    18. 18. Satellite Earth station Earth station Telephone company central office Telephone company central office Telephone company central office Telephone company central office Local loop Microwave tower Microwave tower IXC circuit (interexchange channel) IXC circuit (interexchange channel ) Local loop Wide Area Network 10- User’s modem User’s modem
    19. 19. Types of Networks (cont.) <ul><li>Internet </li></ul><ul><ul><li>Collection of networks </li></ul></ul><ul><ul><li>Public </li></ul></ul><ul><li>Intranet </li></ul><ul><ul><li>Uses Internet network protocols </li></ul></ul><ul><ul><li>Limits accessibility </li></ul></ul><ul><ul><li>Firewall </li></ul></ul><ul><li>Extranet </li></ul><ul><ul><li>For trusted business partners and customers </li></ul></ul>10-
    20. 20. Control of Data Communications Networks <ul><li>Centralized </li></ul><ul><ul><li>Point-of-sale terminals </li></ul></ul><ul><ul><li>Data collection terminals </li></ul></ul><ul><li>Distributed processing </li></ul><ul><ul><li>Receiving computer runs programs that use data </li></ul></ul><ul><li>Client/server processing </li></ul><ul><ul><li>Mixes centralized and decentralized processing strategies </li></ul></ul>10-
    21. 21. Legend : Computer Terminal A Network of Terminals 10-
    22. 22. Legend: Central Computer Distributed Computer A Distributed Processing Network 10-
    23. 23. Communications Hardware <ul><li>Modem </li></ul><ul><ul><li>Converts digital to analog and vice versa </li></ul></ul><ul><ul><li>Bits per second determines transmission speed </li></ul></ul><ul><ul><li>Local loop </li></ul></ul><ul><li>Hub </li></ul><ul><ul><li>Receives a data packet from a computer at one end of one spoke of the star topography and copies its contents to all other computers </li></ul></ul><ul><ul><li>Manageable hubs </li></ul></ul>10-
    24. 24. Data Communications with a Modem Modem Channel Modem A modem is always required between a telephone and a digital computer 10- Computer Computer
    25. 25. Communications Hardware (cont.) <ul><li>Router </li></ul><ul><ul><li>Device that connects many LANs </li></ul></ul><ul><ul><li>More sophisticated than a bridge </li></ul></ul><ul><ul><li>Process header information of a packet </li></ul></ul><ul><li>Switch </li></ul><ul><ul><li>Filters data not intended for a computer on a particular network </li></ul></ul>10-
    26. 26. Communications Connections <ul><li>Private Lines </li></ul><ul><ul><li>Circuit that is always open to communications traffic </li></ul></ul><ul><ul><li>Also called leased line or dedicated line </li></ul></ul><ul><ul><li>Two types </li></ul></ul><ul><ul><ul><li>T-1 - Maximum speed just over 1.5 Mbps </li></ul></ul></ul><ul><ul><ul><li>T-3 - Maximum speed 43 Mbps </li></ul></ul></ul><ul><ul><ul><li>Collections of 64 Kbps connections </li></ul></ul></ul>10-
    27. 27. Communications Connections (cont.) <ul><li>Virtual Private Networks (VPNs) </li></ul><ul><ul><li>Tunneling software makes Internet connections more secure </li></ul></ul><ul><ul><li>Privacy through authentication </li></ul></ul><ul><ul><li>More cost effective than private lines </li></ul></ul>10-
    28. 28. Network Management <ul><li>Digital nervous systems of an organization </li></ul><ul><li>Network planning </li></ul><ul><ul><li>Anticipates firm’s network needs </li></ul></ul><ul><ul><li>Monitor’s performance </li></ul></ul><ul><li>Network Control </li></ul><ul><ul><li>Determines faults </li></ul></ul><ul><ul><ul><li>Errors in data communication </li></ul></ul></ul><ul><ul><ul><li>Alerts to potential faults </li></ul></ul></ul>10-
    29. 29. Network Management (cont.) <ul><li>Network manager </li></ul><ul><ul><li>Planning, implementing, operating, and controlling a firm’s data communications network(s) </li></ul></ul><ul><li>Staff </li></ul><ul><ul><li>Network analysts (a type of systems analyst) </li></ul></ul><ul><ul><li>Software analysts </li></ul></ul><ul><ul><li>Data Communication Technicians (specialize in hardware) </li></ul></ul><ul><ul><li>LAN managers </li></ul></ul>10-
    30. 30. Wireless Networks <ul><li>Cellular networks </li></ul><ul><ul><li>Hand held telephones </li></ul></ul><ul><ul><li>Primarily for voice </li></ul></ul><ul><li>Wireless LANs </li></ul><ul><ul><li>Extensions of regular LANs </li></ul></ul><ul><li>Wide-area wireless networks </li></ul><ul><ul><li>Nationwide </li></ul></ul>10- Highlights in MIS
    31. 31. Wireless Networks (cont.) <ul><li>Paging networks </li></ul><ul><ul><li>Receive only capability </li></ul></ul>Personal Communications Network (PCN) is the networking infrastructure for wireless. It is not yet in place! 10- Highlights in MIS
    32. 32. A Network with Mobility Capability MSS = mobile support station MU = mobile units MU MU MU MU MU MU MU MU MU MU MU MU MSS MSS MSS MSS Fixed host Fixed host Fixed host Fixed host Fixed network 10- Highlights in MIS
    33. 33. Summary <ul><li>Data communications enable computers to share information and applications </li></ul><ul><li>Networks </li></ul><ul><ul><li>LANs </li></ul></ul><ul><ul><li>MANs </li></ul></ul><ul><ul><li>WANs </li></ul></ul><ul><li>Communication standards </li></ul>10-
    34. 34. Summary [cont.] <ul><li>Basic Hardware </li></ul><ul><ul><li>Hubs </li></ul></ul><ul><ul><li>Routers </li></ul></ul><ul><ul><li>Bridges </li></ul></ul><ul><ul><li>Switches </li></ul></ul><ul><li>Planned growth </li></ul>10-
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