IntroductionIntroduction

Data CommunicationData Communication

Communication Communication Sharing informationSharing information : : Local & RemoteLocal & Remote Local Local

Face to face, between individualsFace to face, between individuals RemoteRemote

Over distanceOver distance Requires “telecommunication” media/methodRequires “telecommunication” media/method

TelephonyTelephony TelegraphyTelegraphy TelevisionTelevision

Telecommunication = communication at distance Telecommunication = communication at distance ((tele = far (Greektele = far (Greek))))

Data CommunicationData Communication

Data Data refersrefers to to FactsFacts ConceptsConcepts InstructionsInstructions

PresentedPresented in any form in any form agreed upon by agreed upon by the parties creating and using the the parties creating and using the datadata

In computer information systemIn computer information system Data are represented by Data are represented by 0/10/1

Data CommunicationData Communication

In summaryIn summary Data communication = the exchange Data communication = the exchange

of data (0s/1s) between two devices of data (0s/1s) between two devices via some form of transmission media via some form of transmission media (i.e. cable)(i.e. cable)

LocalLocal communication communication Devices are in the same buildingDevices are in the same building

RemoteRemote communication communication Devices are far apartDevices are far apart

Data CommunicationData Communication

Data communication process Data communication process to to occuroccur

hardware hardware communication devices communication devices Software Software communication software communication software

Data CommunicationData Communication

Three fundamental characteristics Three fundamental characteristics (provide data communication system (provide data communication system effectiveness)effectiveness)

DeliveryDelivery (to the right party) (to the right party) AccuracyAccuracy (0 (0 0 / 1 0 / 1 1 NOT 0 1 NOT 0 1 ) 1 ) TimelinessTimeliness

ComponentsComponents

t

Step1 :Step2:Step3:……

Step1 :Step2:Step3:……

ProtocolProtocolmessage

medium

sender receiver

ComponentsComponents

MessagesMessages Data to be communicatedData to be communicated Any form (text, pictures, sound, video, etc.)Any form (text, pictures, sound, video, etc.)

Sender/ReceiverSender/Receiver Device that sends/receives the data Device that sends/receives the data

messagemessage It can be : computer, telephone, etc.It can be : computer, telephone, etc.

MediumMedium Twisted pair wire, coaxial cable, etc.Twisted pair wire, coaxial cable, etc.

Protocol : Rules.Protocol : Rules.

NetworksNetworks

A set of devices (node) connected by A set of devices (node) connected by media linksmedia links

A node can beA node can be Computer Computer PrinterPrinter Any other devices capable of sending and Any other devices capable of sending and

receiving datareceiving data The link is often called The link is often called “communication “communication

channel”channel” UsesUses “Distributed Processing” “Distributed Processing”

NetworksNetworks Network CriteriaNetwork Criteria

Data communication network criteria

Reliability

SecurityPerformance

NetworksNetworks Network CriteriaNetwork Criteria

Data communication network criteria

Reliability

SecurityPerformance

Network CriteriaNetwork Criteria

PerformancePerformance measures measures

Transit timeTransit time Traveling time from one device to anotherTraveling time from one device to another

Response timeResponse time Time between an inquiry and a responseTime between an inquiry and a response

Network Criteria : Network Criteria : PerformancePerformance

Important Factors (for performance)Important Factors (for performance) Number of usersNumber of users Type of transmission mediumType of transmission medium HardwareHardware SoftwareSoftware

NetworksNetworks Network CriteriaNetwork Criteria

Data communication network criteria

Reliability

SecurityPerformance

Network CriteriaNetwork Criteria

ReliabilityReliability : measured by : measured by

Frequency of failuresFrequency of failures Recovery time of a network after failureRecovery time of a network after failure Protected from unforeseen damageProtected from unforeseen damage

FireFire FloodFlood etc.etc.

NetworksNetworks Network CriteriaNetwork Criteria

Data communication network criteria

Reliability

SecurityPerformance

Network CriteriaNetwork Criteria

SecuritySecurity : Protecting data from : Protecting data from unauthorised access and virusesunauthorised access and viruses Unauthorised accessUnauthorised access

PasswordPassword EncryptionEncryption

VirusesViruses A good network must be protected from A good network must be protected from

viruses by hardware and softwareviruses by hardware and software

ApplicationsApplications Marketing and salesMarketing and sales Financial servicesFinancial services ManufacturingManufacturing Electronic messagingElectronic messaging Directory servicesDirectory services Information servicesInformation services Electronic data interchange (EDI)Electronic data interchange (EDI) TeleconferencingTeleconferencing Cellular telephoneCellular telephone Cable televisionCable television

Protocols and StandardsProtocols and Standards

ProtocolsProtocols A set of rules that govern data A set of rules that govern data

communication communication DefinesDefines

What is communicatedWhat is communicated How it is communicatedHow it is communicated When it is communicatedWhen it is communicated

Key elements of a protocolKey elements of a protocol SyntaxSyntax SemanticsSemantics timingtiming

Protocols and StandardsProtocols and Standards

SyntaxSyntax Format of data : i.e. the first 8 bits = sender addressFormat of data : i.e. the first 8 bits = sender address

the second 8 bits = receiver addressthe second 8 bits = receiver address

the rest = data or messagethe rest = data or message

SemanticSemantic Meaning of each section of bitsMeaning of each section of bits How is a pattern to be interpretedHow is a pattern to be interpreted What action is to be takenWhat action is to be taken i.e. i.e. does the does the addressaddress identify the identify the routeroute to be to be

taken or the taken or the final destinationfinal destination of the message of the message

Protocols and StandardsProtocols and Standards

Timing Timing When data should be sentWhen data should be sent How fast they can be sentHow fast they can be sent For example :For example :

Sender produces 100 Mbps Sender produces 100 Mbps sender can sender can receive 1 Mbpsreceive 1 Mbps

Overload the receiverOverload the receiver Data lostData lost

StandardsStandards

Facts:Facts: Devices from different manufacturers Devices from different manufacturers Different signal/methods/dataDifferent signal/methods/data

Standards are necessaryStandards are necessary Data communication standardsData communication standards

de facto de facto (by fact or by convention)(by fact or by convention) de jure de jure (by law or by regulation) (by law or by regulation)

Standards organisationsStandards organisations Standards creation committeeStandards creation committee

ISOISO CCITTCCITT ANSIANSI IEEEIEEE EIAEIA

ForumsForums Frame Relay ForumFrame Relay Forum ATM Forum and ATM ConsortiumATM Forum and ATM Consortium ISOC and IETFISOC and IETF