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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