MANAGEMENT INFORMATION SYSTEMS 8/E

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Chapter 10

Data Communications

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

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Objectives

Q Understand data communication basics.

Q Know the data transmission speed for communication

between computers.

Q Be familiar with local area networks, metropolitan area

networks, wide area networks, and the Internet of networks.

Q Understand the two main local area network

protocols--Token-Ring and Ethernet.

Q Understand the data communication services provided

by public telephone systems, also known as common carriers.

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Communication Basics

Q

Computer communications is at

three levels

–

– Application levelApplication level

–

– Computer levelComputer level

–

– Communication channelCommunication channel

Q

Protocol

–

– Set of rules for communicationsSet of rules for communications

–

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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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ISO

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Protocols for Computer

Communication

Q

Early computers

–

– TerminalsTerminals –

– Sneaker netSneaker net Q

Q

System Network Architecture (SNA)

–

– Established by IBM in 1974Established by IBM in 1974 –

– ProprietaryProprietary Q

Q

Token-Ring

–

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Protocols for Computer

Communication

Q

Ethernet

–

– Xerox working with Intel and DigitalXerox working with Intel and Digital

Equipment Corporation developed this protocol

–

– Non-proprietaryNon-proprietary –

– Defined by IEEEDefined by IEEE –

– Works on a single transmission lineWorks on a single transmission line –

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Packets

Q

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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Network Addresses

Q

Address

–

– Four-part set of numbersFour-part set of numbers –

– Each from 0 to 255Each from 0 to 255 Q

Q

Internet Service Providers (ISPs)

–

– User connects through common carrierUser connects through common carrier Q

Q

Serial Line Internet Protocol (SLIP) and

Point-to-Point Protocol (PPP)

–

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Protocols for Public Phone

Systems

Q Q

X.25

– – analoganalog –

– older protocololder protocol Q

Q

Integrated Services Digital Network (ISDN)

–

– DigitalDigital –

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Protocols for Public Phone

Systems (

cont

_cont

.)

_.)

Q

Frame Relays

–

– Move to fiber opticsMove to fiber optics Q

Q

Asynchronous Transfer Mode (ATM)

–

– Smaller packet sizeSmaller packet size –

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Data Communications Links the

General Systems Model Elements

Standards

Management Information

processor Environment

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Networks

Q

Each device must be connected to the

communications medium via a network

interface card (NIC)

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Types of Networks

Q

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 Q

Q

MAN (metropolitan area networks)

–

– spans one city/metropolitan areaspans one city/metropolitan area Q

Q

WAN (wide area network)

–

– Covers a large geographic areaCovers a large geographic area

–

– Includes a wide variety of circuitsIncludes a wide variety of circuits

–

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Users Users Manager 1 Manager 1 Secretary 1 Secretary 1 Secretary 2 Secretary 2 Workstation Workstation 1 1 Workstation Workstation 2 2 Workstation Workstation 3 3 Workstation Workstation 4 4 Manager 2 Manager 2 Network Network Server Server Hard Hard Disk Disk Letter Quality Letter Quality Printer Printer Plotter Plotter

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Common LAN Topologies

Star

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Common LAN Topologies

Ring

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Common LAN Topologies

Bus

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Satellite Satellite Earth Earth station station Earth Earth station station Telephone Telephone company company central office central office Telephone Telephone company company central office central office Telephone Telephone Telephone Telephone company company central office central office Local Local loop loop User’s User’s modem modem Microwave Microwave tower tower Microwave Microwave tower tower IXC circuit IXC circuit ( (interexchangeinterexchange channel) channel) IXC circuit (interexchange channel) Local Local loop loop

Wide Area Network

User’s

modem

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Types of Networks (

cont

.)

Q

Internet

–

– Collection of networksCollection of networks –

– PublicPublic Q

Q

Intranet

–

– Uses Internet network protocolsUses Internet network protocols –

– Limits accessibilityLimits accessibility –

– FirewallFirewall Q

Q

Extranet

–

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Control of Data Communications

Networks

Q

Centralized

–

– Point-of-sale terminalsPoint-of-sale terminals –

– Data collection terminalsData collection terminals Q

Q

Distributed processing

–

– Receiving computer runs programs that useReceiving computer runs programs that use data

data

Q

Client/server processing

–

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Legend:

A Network of Terminals

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Legend:

Central Distributed

A Distributed Processing Network

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Communications Hardware

Q

Modem

–

– 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 Q

Q

Hub

–

– Receives a data packet from a computer at oneReceives a data packet from a computer at one end of one spoke of the star topography and

end of one spoke of the star topography and

copies its contents to all other computers

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Data Communications with a Modem

Computer

Modem

Modem ChannelChannel ModemModem Computer

Computer

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

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Communications Hardware (

cont

.)

Q

Router

–

– 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 Q

Q

Switch

–

– Filters data not intended for a computer on aFilters data not intended for a computer on a particular network

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Communications Connections

Q

Private Lines

–

– Circuit that is always open to communicationsCircuit that is always open to communications traffic

traffic

–

– Also called leased line or dedicated lineAlso called leased line or dedicated line –

– Two typesTwo types »

» T-1 - Maximum speed just over 1.5 T-1 - Maximum speed just over 1.5 MbpsMbps »

» T-3 - Maximum speed 43 T-3 - Maximum speed 43 MbpsMbps »

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Communications Connections

(

cont

_cont

.)

_.)

Q

Virtual Private Networks (

VPNs

)

–

– Tunneling software makes Internet connectionsTunneling software makes Internet connections more secure

more secure

–

– Privacy through authenticationPrivacy through authentication –

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Network Management

Q

Digital nervous systems of an organization

Q

Network planning

–

– Anticipates firm’s network needsAnticipates firm’s network needs –

– Monitor’s performanceMonitor’s performance Q

Q

Network Control

–

– Determines faultsDetermines faults »

» Errors in data communicationErrors in data communication »

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Network Management (

cont

_cont

.)

_.)

Q

Network manager

–

– Planning, implementing, operating, andPlanning, implementing, operating, and controlling a firm’s data communications

controlling a firm’s data communications

network(s)

Q

Staff

–

– Network analysts (a type of systems analyst)Network analysts (a type of systems analyst) –

– Software analystsSoftware analysts –

– Data Communication Technicians (specialize inData Communication Technicians (specialize in

hardware)

–

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Wireless Networks

Q

Cellular networks

–

– Hand held telephonesHand held telephones –

– Primarily for voicePrimarily for voice Q

Q

Wireless LANs

–

– Extensions of regular LANsExtensions of regular LANs Q

Q

Wide-area wireless networks

–

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Wireless Networks (

cont

_cont

.)

_.)

Q

Paging networks

–

– Receive only capabilityReceive only capability

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

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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

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Summary

Q

Data communications enable computers to

share information and applications

Q Q

Networks

– – LANsLANs – – MANsMANs – – WANsWANs Q

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Summary [cont.]

Q

Basic Hardware

– – HubsHubs – – RoutersRouters – – BridgesBridges – – SwitchesSwitches Q