Computer Network - #01
Transcript of Computer Network - #01
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Computer Network
Computer Science, Brawijaya University
August 2007
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Course Outline
NetworkDefinition
NetworkClassification
NetworkComponent
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About The Past
InternetstartedbyARPANET
4Nodepresented4University,calledInternet
MessageProcessor(IMPs)using1822
Protocol(IENDocuments#1822)
Late,1972fundedbyUSMilitaryandrenamedDARPA
FinallycallInternet,runningunderIPProtocol
Suite,definedinRFC791(IP)andRFC
793(TCP)
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About The Past
BasicprinciplesofTCP/IPwerepublishedin
1974
AdoptionoftheDomainNameSystem(DNS)
in1983
EstablishmentoftheInternetEngineeringTaskForce(IETF)in1989
Formalre-namingoftheARPANETasthe
Internetin1990
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But What is a Network .. ?
Acombinationofhardware,software,and
media,whichtogetherallowmultiple
computingdevicestocommunicatewitheachother
Inshort,anetworkgivescomputerstheabilitytocommunicate.However,thatdefinition
couldapplytoalotofdifferenttypesof
networksAndthiscoursewilltalkaboutTCP/IPand
Ethernet
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But What is a Network .. ?
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Network Classification
ByLayer Accordingtosomebasic
referencesmodellikeOSIandInternet
ProtocolSuite
ByScale Accordingtothecoveragearea,
Local,Campus,Metropolitan,WideByConnectionMethod Ethernet,Wireless,
DialUp,PowerLineCommunication
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Network Classification
ByFunctionalRelationship ClientServer,
PeertoPeer,ActiveNetwork
ByTopology accordingtothenetwork
topology uponwhichthenetworkisbased:
Bus,Star,Ring,Mesh,TreeorHierarchical,etc
ByProtocol Computernetworksmaybe
classifiedaccordingtothecommunicationsprotocol thatisbeingusedonthenetworklike
ISDN,PDH,RS-232,SDH,SONET
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Network Components
NIC,NetworkInterfaceCard,istheexpansioncardinstallinacomputerto
connect,orinterfaceforacomputertonetwork.
HUB,ahubisthedevicethatconnectsallthe
segmentsofthatnetworktogether.SWITCH,Likeahub,aswitchconnects
multiplesegmentsofanetworktogether,with
oneimportantdifference.Whereasahubbroadcastsdata,switchforwardittocertainport
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Network Components
BRIDGE,anetworkdevicethatconnectstwo
similarnetworksegmentstogether.The
primaryfunctionofabridgeistokeeptrafficseparatedonbothsidesofthebridge
ROUTER,isanetworkdevicethatconnectsmultiple,oftendissimilar,networksegments
intoaninternetwork
GATEWAY,isanyhardwareandsoftwarecombinationthatconnectsdissimilarnetwork
environments.
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How to Eat T-Rex, ISO OSI Model
Aprotocolsuiteismosteasilydefinedasasetofrulesusedtodeterminehowcomputers
communicatewitheachother.Itissimilartolanguage
Themostcommonlyreferencedprotocol
model,OSImodel,wasdevelopedin1977bytheInternationalOrganizationforStandardizationtoprovidecommonground
whendescribinganynetworkprotocolTheOSImodelisusedtodescribewhattasks
aprotocolsuiteperformsasyouexplorehow
datamovesacrossanetwork
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OSI Model
TheOSIModel
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OSI Model
Youcanusemnemonicdevicestohelpyou
remembertheorderoftheOSImodellayers:
APSTNDP(fromtoptobottom).
Themostpopularmnemonicforthis
arrangementisAllPeopleSeemToNeedDataProcessing.
Areversemnemonic(fromPhysicalto
Application,bottomtotop)isPleaseDoNotThrowSausagePizzaAway.
Goodadvice,dontyouthink?
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OSI Model
PhysicalLayer
Generallyspeaking,Physicallayerconceptsdeal
withanetworkcomponentthatistangibleormeasurable
Additionally,thePhysicallayerspecifieshow
muchofthemediawillbeused(inotherwords,itssignalingmethod)duringdatatransmission
Ifanetworksignal usesallavailablesignal
frequencies(or,toputitdifferently,theentirebandwidth),thetechnologyissaidtouse
basebandsignaling
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OSI Model
DataLinkLayer
TheDataLinklayerisactuallymadeupoftwo
sublayers :MediumAccessControlandLogicalLinkControl
ProtocolsthatoperateattheDataLinklayerhave
severalresponsibilities,includingcreating,transmitting,andreceivingpackets.Additionally,
theDataLinklayerisresponsibleforphysical
(MAC)addressingandlogicallinkcontrol(LLC)processing,creatinglogicaltopologies,and
controllingmediaaccess
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OSI Model
NetworkLayer
TheNetworklayeroftheOSImodeldefines
protocolsthatensurethatthedataarriveatthecorrectdestination.Thisisprobablythemost
commonlydiscussedlayeroftheOSImodel.
ThemostimportantNetworklayerconceptsare:LogicalnetworkaddressingandRouting
IftheMACaddressistheDataLinklayer
physicaladdress,theprotocol-addressingschemeattheNetworklayerdefinesthelogical
address
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OSI Model
TransportLayer
TheTransportlayerdefinestheprotocolsfor
structuringmessagesandchecksthevalidityoftransmissions
KeyWord:Reliableend-to-enderrorandflow
control
TheprotocolsthatoperateattheTransportlayer
mainlyensurereliablecommunicationsbetween
upperpeerlayers
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OSI Model
SessionLayer
ProtocolsthatoperateattheSessionlayerofthe
OSImodelareresponsibleforestablishing,maintaining,andbreakingsessions,ordialogs
Thisisdifferentfromtheconnectionservices
providedattheTransportlayer
Sessionlayeroperatesatahigherleveland
looksatthebiggerpicturetheentire
conversation,notjustonesentence.ManygatewaysoperateattheSessionlayer
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OSI Model
PresentationLayer
ThePresentationlayerdoeswhatyoumightthink
itdoes:Itchangesthelook,orpresentation,ofthedatafromthelowerlayersintoaformatthat
theupper-layerprocessescanworkwith
Amongotherservices,thePresentationlayerdealswithencryption,datacompression,and
networkredirectors
Inaddition,thePresentationlayerdealswithcharacter-settranslation
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OSI Model
ApplicationLayer
NowIknowwhatyoumightbethinking:This
layerisformyprograms,right?Wrong
TheApplicationlayerdefinesseveralstandard
networkservicesthatfallintocategoriessuchas
filetransfer,printaccess,ande-mailrelay
Theapplicationsthataccessthesenetwork
servicesarelocatedabovetheApplicationlayer
(althoughsomepeoplesaythatapplicationsareanextensionoftheApplicationlayer)
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Networking Protocol The TCP/IP
TCP/IPisawidelypublishedopenstandardandiscompletelyindependentofany
hardwareorsoftwaremanufacturerTCP/IPcansenddatabetweendifferent
operatingsystems,fromsmallPCsallthe
waytomainframesandeverythinginbetween
TCP/IPisseparatedfromtheunderlying
hardwareandwillrunoverEthernet,TokenRing,orX.25networksand
evenoverdial-uptelephonelines
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Networking Protocol The TCP/IP
TCP/IPisaroutableprotocol,whichmeansit
cansenddatagrams overaspecificroute,
thusreducingtrafficonotherpartsofthenetwork
TCP/IPhasreliableandefficientdata-delivery
mechanisms
TCP/IPusesacommonaddressingscheme.
Therefore,anysystemcanaddressanyothersystem,eveninanetworkaslargeasthe
Internet
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TCP/IP Protocol
TheTransmissionControlProtocol/Internet
Protocol(TCP/IP)istheprotocolofchoice
todayLikeotherprotocols,isusedtoallowtwo
computerstocommunicateoveranetwork
However,TCP/IPisusednotonlyonlocal
areanetworks,butalsooverwidearea
networksandtheInternetActually,TCP/IPistheonlyprotocolinuseon
theInternet
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TCP/IP Protocol
AndWhatareTCP/IPDo?
Addressing.Eachhostisgiven(eithermanually
orautomatically)adotteddecimalIPaddressintheformatxxx.xxx.xxx.xxx wherexxxisanumberfrom0to255
Routing.OnTCP/IPnetworks,routingisafairlyinvolvedprocess.Inordertosendapacketthroughaninternetwork (liketheInternet),theroutermusthavethreepiecesofinformation:the
IPaddressofthesender,theIPaddressofthedestination,andtheIPaddressofthenextroutertowhichthepacketshouldbesent
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TCP/IP Protocol
AndWhatareTCP/IPDo?
Naming.TCP/IPhostsarenamedaccordingto
theDNSconvention.DNSisaservicethatresolvesnamestoIPaddressessothatwecan
usefriendlynameslikewww.trainsolutions.com
torefertocomputersinsteadofunfriendlyIPaddresseslike192.168.24.31
More..trytonameitbyyours
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TCP/IP Protocol
OSIModelandTCP/IP
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References
MartinP.Clark,DataNetworks,IPandThe
Internet.JohnWiley&Sons,2003
Wendell Odom,ComputerNetworking,First-Step.CiscoPress,April2004
DavidGroth,Network+StudyGuide,ThirdEdition.Sybex,2002