Chap10

Chapter 10Data CommunicationsData Communications

MANAGEMENT INFORMATION SYSTEMS 8/ERaymond McLeod, Jr. and George Schell

Copyright 2001 Prentice-Hall, Inc.

10-1

Communication BasicsCommunication Basics

Computer communications is at Computer communications is at three levelsthree levels– Application level Application level – Computer levelComputer level– Communication channelCommunication channel

Protocol Protocol – Set of rules for communicationsSet of rules for communications– OSI StandardOSI Standard

10-2

OSI Reference ModelOSI 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

10-3

ISO WebsiteISO Website

10-4

Protocols for Computer Protocols for Computer CommunicationCommunication

Early computersEarly computers– TerminalsTerminals– Sneaker netSneaker net

System Network Architecture (SNA)System Network Architecture (SNA)– Established by IBM in 1974Established by IBM in 1974– ProprietaryProprietary

Token-RingToken-Ring– Host computer controlledHost computer controlled– peer-to-peerpeer-to-peer

10-5

Protocols for Computer Protocols for Computer CommunicationCommunication

EthernetEthernet– Xerox working with Intel and Digital Xerox working with Intel and Digital

Equipment Corporation developed this protocolEquipment Corporation developed this protocol– Non-proprietaryNon-proprietary– Defined by IEEEDefined by IEEE– Works on a single transmission lineWorks on a single transmission line– No token is passedNo token is passed

10-6

PacketsPackets

Piece of the total data to be communicated, Piece of the total data to be communicated, combined with the address of the destination combined with the address of the destination computer for the data and other control computer for the data and other control information.information.

Transmission Control Protocol/Internet Protocol (TCP/IP) is one of the more important packet switching protocols

10-7

Network AddressesNetwork Addresses

Address Address – Four-part set of numbers Four-part set of numbers – Each from 0 to 255Each from 0 to 255

Internet Service Providers (ISPs)Internet Service Providers (ISPs)– User connects through common carrierUser connects through common carrier

Serial Line Internet Protocol (SLIP) and Serial Line Internet Protocol (SLIP) and Point-to-Point Protocol (PPP)Point-to-Point Protocol (PPP)– Protocols for users at homeProtocols for users at home

10-8

Protocols for Public Phone Protocols for Public Phone SystemsSystems

X.25X.25– analoganalog– older protocololder protocol

Integrated Services Digital Network (ISDN)Integrated Services Digital Network (ISDN)– Digital Digital – Can carry voice, data, and videoCan carry voice, data, and video

10-9

Protocols for Public Phone Protocols for Public Phone Systems (cont.)Systems (cont.)

Frame RelaysFrame Relays– Move to fiber opticsMove to fiber optics

Asynchronous Transfer Mode (ATM)Asynchronous Transfer Mode (ATM)– Smaller packet sizeSmaller packet size– Faster transmission speedsFaster transmission speeds

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Data Communications Links theData Communications Links theGeneral Systems Model ElementsGeneral Systems Model Elements

Standards

Management Informationprocessor

Environment

Input Transformation Output

10-11

NetworksNetworks

Each device must be connected to the Each device must be connected to the communications medium via a network communications medium via a network interface card (NIC)interface card (NIC)

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Types of NetworksTypes of Networks

LAN (local area network)LAN (local area network)– Limited area but could include 100 or so microsLimited area but could include 100 or so micros– Facilitates office automationFacilitates office automation

MAN (metropolitan area networks)MAN (metropolitan area networks)– spans one city/metropolitan areaspans one city/metropolitan area

WAN (wide area network)WAN (wide area network)– Covers a large geographic areaCovers a large geographic area– Includes a wide variety of circuits Includes a wide variety of circuits – Usually includes host computersUsually includes host computers

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UsersUsers

Manager 1Manager 1

Secretary 1Secretary 1

Secretary 2Secretary 2

WorkstationWorkstation11




Manager 2Manager 2

NetworkNetworkServerServer

HardHardDiskDisk

Letter QualityLetter QualityPrinterPrinter

PlotterPlotter

A Local Area NetworkA Local Area Network 10-14

Common LAN TopologiesCommon LAN TopologiesStarStar

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Common LAN TopologiesCommon LAN TopologiesRingRing

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Common LAN TopologiesCommon LAN TopologiesBusBus

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SatelliteSatellite

EarthEarthstationstation

EarthEarthstationstation

TelephoneTelephonecompanycompanycentral officecentral office




LocalLocallooploop

User’sUser’smodemmodem

MicrowaveMicrowave towertower

MicrowaveMicrowave towertower

IXC circuitIXC circuit(interexchange(interexchange

channel)channel)

IXC circuit

(interexchange channel)

LocalLocallooploop

Wide Area Wide Area NetworkNetwork

User’sUser’smodemmodem

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Types of Networks (cont.)Types of Networks (cont.)

InternetInternet– Collection of networksCollection of networks– PublicPublic

IntranetIntranet– Uses Internet network protocolsUses Internet network protocols– Limits accessibilityLimits accessibility– FirewallFirewall

ExtranetExtranet– For trusted business partners and customersFor trusted business partners and customers

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Control of Data Control of Data Communications NetworksCommunications Networks CentralizedCentralized

– Point-of-sale terminalsPoint-of-sale terminals– Data collection terminalsData collection terminals

Distributed processingDistributed processing– Receiving computer runs programs that use dataReceiving computer runs programs that use data

Client/server processingClient/server processing– Mixes centralized and decentralized processing Mixes centralized and decentralized processing

strategiesstrategies

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Legend:

Computer Terminal

A Network of TerminalsA Network of Terminals

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Legend:

CentralComputer

DistributedComputer

A Distributed Processing A Distributed Processing NetworkNetwork

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Communications HardwareCommunications Hardware

ModemModem– Converts digital to analog and vice versaConverts digital to analog and vice versa– Bits per second determines transmission speedBits per second determines transmission speed– Local loopLocal loop

Hub Hub – Receives a data packet from a computer at one end Receives a data packet from a computer at one end

of one spoke of the star topography and copies its of one spoke of the star topography and copies its contents to all other computerscontents to all other computers

– Manageable hubsManageable hubs

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Data Communications with a Data Communications with a ModemModem

ComputerComputerModemModem ChannelChannel ModemModemComputerComputer

A modem is always required between a telephone and a digital computer

10-24

Communications Hardware Communications Hardware (cont.)(cont.)

RouterRouter– Device that connects many LANsDevice that connects many LANs– More sophisticated than a bridgeMore sophisticated than a bridge– Process header information of a packetProcess header information of a packet

SwitchSwitch– Filters data not intended for a computer on a Filters data not intended for a computer on a

particular networkparticular network

10-25

Communications Communications ConnectionsConnections

Private LinesPrivate Lines– Circuit that is always open to communications Circuit that is always open to communications

traffictraffic– Also called leased line or dedicated lineAlso called leased line or dedicated line– Two typesTwo types

» T-1 - Maximum speed just over 1.5 MbpsT-1 - Maximum speed just over 1.5 Mbps

» T-3 - Maximum speed 43 MbpsT-3 - Maximum speed 43 Mbps

» Collections of 64 Kbps connectionsCollections of 64 Kbps connections

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Communications Communications Connections (cont.)Connections (cont.)

Virtual Private Networks (VPNs)Virtual Private Networks (VPNs)– Tunneling software makes Internet connections Tunneling software makes Internet connections

more securemore secure– Privacy through authenticationPrivacy through authentication– More cost effective than private linesMore cost effective than private lines

10-27

Network ManagementNetwork Management

Digital nervous systems of an organizationDigital nervous systems of an organization Network planningNetwork planning

– Anticipates firm’s network needsAnticipates firm’s network needs– Monitor’s performanceMonitor’s performance

Network ControlNetwork Control– Determines faultsDetermines faults

» Errors in data communicationErrors in data communication

» Alerts to potential faultsAlerts to potential faults

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Network Management Network Management (cont.)(cont.)

Network managerNetwork manager– Planning, implementing, operating, and controlling a Planning, implementing, operating, and controlling a

firm’s data communications network(s)firm’s data communications network(s) StaffStaff

– Network analysts (a type of systems analyst)Network analysts (a type of systems analyst)– Software analysts Software analysts – Data Communication Technicians (specialize in Data Communication Technicians (specialize in

hardware)hardware)– LAN managersLAN managers

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Wireless NetworksWireless Networks

Cellular networksCellular networks– Hand held telephonesHand held telephones– Primarily for voicePrimarily for voice

Wireless LANs Wireless LANs – Extensions of regular LANsExtensions of regular LANs

Wide-area wireless networksWide-area wireless networks– NationwideNationwide

10-30Highlights in MIS

Wireless Networks (cont.)Wireless Networks (cont.)

Paging networksPaging networks– Receive only capabilityReceive only capability

Personal Communications Network (PCN) is the networking infrastructure for wireless.

It is not yet in place!


A Network with Mobility A Network with Mobility CapabilityCapability

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


SummarySummary

Data communications enable computers to Data communications enable computers to share information and applicationsshare information and applications

NetworksNetworks– LANsLANs– MANsMANs– WANsWANs

Communication standardsCommunication standards

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Summary [cont.]Summary [cont.]

Basic HardwareBasic Hardware– HubsHubs– RoutersRouters– BridgesBridges– SwitchesSwitches

Planned growthPlanned growth

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Business

Chap10