1. Chapter 10 Data Communications MANAGEMENT INFORMATION SYSTEMS 8/E
Raymond McLeod, Jr. and George Schell
Chapter 10
Data Communications
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Copyright 2001 Prentice-Hall, Inc. 1

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