CN Unit-1 Part-1 notes very useful iiiiiii.pdf

computer network notes of professor sp chauhan

1. 1
S.P. Chauhan
MAHARAJA SURAJMAL INSTITUTE
Department of Computer Applications
Unit –1 (Part –1)
Computer Networks
(BCA-201)
Mr. S.P. Chauhan
Asst. Prof. & Hostel Warden

2. Course Outcomes
LEARNINGOBJECTIVES:-Inthiscourse,thelearnerswillbeabletodevelop
expertiserelatedtothefollowing:-
1.Tostudydifferenttypesofmedia,multiplexing,switchednetworks,the
Internet,TCP/IPsuite,fiber-opticcommunicationsandthestate-of-art
networkingapplications.
2.Todevelopanunderstandingofdifferentcomponentsofcomputer
networks,variousprotocols,moderntechnologiesandtheirapplications.
3.IdentifyanddiscusstheunderlyingconceptsofIPv4&IPv6protocols,
alongwiththeircharacteristicsandfunctionality.
4.DetailsofIPoperationsintheInternetandassociatedroutingprinciples.
5.Analyzingvariouslayeringprotocolsincomputernetworks.
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S.P. Chauhan

3. Course Outcomes
1.CO1:Utilizethefundamentalsofdatacommunicationand
networkingtoidentifythetopologiesandconnectingdevicesof
networks.
2.CO2:Understandanddescribethelayeredprotocolmodel(OSIand
TCP/IPmodel)
3.CO3:Analyzetheelementsandprotocolsforpeer–peerand
communicationbetweenlayers.
4.CO4:EvaluateandimplementroutingalgorithmsandRouterbasic
configuration.
5.CO5:EvaluatetheprotocolsandPrinciplesincomputernetworking
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4. Course Outcomes
INSTRUCTIONS TO PAPER SETTERS:
1.QuestionNo.1shouldbecompulsoryandcovertheentiresyllabus.
Thereshouldbe10questionsofshortanswertypeof2/2.5markseach,
havingatleast2questionsfromeachunit.
2.ApartfromQuestionNo.1,restofthepapershallconsistoffourunitsas
perthesyllabus.Everyunitshouldhavetwoquestionstoevaluate
analytical/technicalskillsofcandidate.However,studentmaybeasked
toattemptonly1questionfromeachunit.Eachquestionshouldbeof
10/12.5marks,includingitssubparts,ifany.
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5. Syllabus
Unit1–BasicConcepts:Componentsofdatacommunication,distributed
processing,Lineconfiguration,topology,transmissionmode,andcategoriesof
networks.
OSIandTCP/IPModels:Layersandtheirfunctions,comparisonofmodels.
TransmissionMedia:Guidedandunguided,Attenuation,distortion,noise,
throughput,propagationspeedandtime,wavelength,ShannonCapacity
Unit2-Telephony:Multiplexing,WDM,TDM,FDM,circuitswitching,packet
switchingandmessageswitching.
DataLinkLayer:Typesoferrors,Framing(characterandbitstuffing),error
detection&correctionmethods;Flowcontrol;Protocols:Stop&waitARQ,Go-
Back-NARQ,SelectiverepeatARQ.
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6. Syllabus
Unit3-NetworkLayer:Internetworking&Devices:Repeaters,Hubs,Bridges,
Switches,Router,Gateway,Modems.
Addressing:IPv4andIPv6addressing,IPv4subnetting;Routing:UnicastRouting
Protocols:RIP,OSPF,BGP.
Routing:RoutingMethods-StaticandDynamicRouting,Routingbasiccommands,
Distancevectorprotocol,Linkstateprotocol.
Unit4-TransportandupperlayersinOSIModel:Transportlayerfunctionsand
Protocols,connectionmanagement,functionsofsessionlayers,Presentationlayer,
andApplicationlayer.
•TEXTBOOKS:
1.[TB1].A.S.Tenanbaum,“ComputerNetworks”;PearsonEducationAsia,4thEd.,
2003.
2.[TB2].BehrouzA.Forouzan,“DataCommunicationandNetworking”,2nd
edition,TataMcGrawHill.
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7. Basic Concepts
Today’slongdistancecommunicationinvolvethetransmissionandreceptionofalarge
amountofdata/informationinashortperiodoftime.Thedayshavegonewhenpeople
reliedonhumanmessengers,postalservices,newspapersorevenpigeonstosendand
receivetheinformation.
Allthesemethodswereevolutionarysteps,whichhaveleadstotoday’smodern
technologiesoflongdistancecommunication.Today’slongdistancecommunication
involvethetransmissionandreceptionofalargeamountofinformationinashortperiod
oftime.
Thecomputernetworkplayanintegralroleincomputercommunication.Thenetwork
notonlyconnectcomputersinourorganizationsbutcanalsolinkustoothercomputers
acrossthenationandaroundtheworld.Itallowthepeopletoaccesstheinformation
availableatremotecomputerwithminimumtime.Sonetworkisawayoftransmitting
andreceivingthedataorinformationfromoneorvariousresources.
Earlierthecomputerswereisolatedandlargelyincompatible.Buttodaynetworksupport
communicationformcomputertocomputeraswell.Thecomputersystemcanrequest
andreceiveservicesfromothercomputersautomaticallyandinvisiblytotheuser.
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S.P. Chauhan

8. Basic Concepts
Network:-Anetworkisasetofdevicesreferredtoasnodesconnectedbymedia
links.Anodecanbeacomputer,printeroranyotherdevicecapableofsendingor
receivingdatageneratedbyothernodeonthenetwork.Thelinksconnecting
devicesarecalledcommunicationchannels.
Thebasicaimofdatacommunicationandnetworkingistobeabletoexchangedata
suchastext,audioandvideofromonepointtoanotherpointintheworld.
BasicCommunicationModel:-Thefundamentalpurposeofcommunicationsystemis
toexchangethedatabetweentwopointsorparties.Dependinguponthebasic
communicationmodel,fig.givenbelowshowssimpleandbasiccommunication
model.
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A general communication model

9. Basic Concepts
BasicCommunicationModel:-Followingarekeyelementofbasiccommunicationmodel.
1.Source:-Itisthedevicethatgeneratesthedatatobetransmittedeg.Telephones&P.C.
2.Transmitter:-Ittransformandencodestheinformationinsuchamannersoasto
produceelectromagneticwavesorsignals.TheseElectromagneticwavesorsignalscan
betransmittedacrosssomesortoftransmissionsystemeg.Amodemtakesadigitalbit
streamfromanattacheddevicesuchasP.C.andtransformthatbitstreamintoanalog
signal.
3.TransmissionSystem:-Itcanbeasingletransmissionlineoracomplexnetwork
connectingsourceanddestination.
4.Receiver:-Itacceptsthesignalfromthetransmissionsystemandconvertsitintoaform
whichcanbehandledbythedestinationdeviceeg.Amodemacceptsananalogsignal
comingfromnetworkortransmissionlineandconvertsitintoadigitalbitstream.
5.Destination:-Ittakestheincomingdatafromthereceiver.
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Fig. Establishment
of communication

10. Basic Concepts
Datareferstoinformationpresentedinwhateverformisagreeduponbytheparties
creatingandusingthedata.
Telecommunication,includestelephony,telegraphy,andtelevision,means
communicationatadistance(teleisGreekfor"far").
DataCommunication:-Inourdailylifewecommunicateandshareinformation.This
sharinginformationmaybelocalorremote.Generallylocalcommunicationtakes
placeface-to-facebetweenindividualswhereasremotecommunicationtakesplace
overdistance.Thetermcommunicationincludestelephony,telegraphyandtelevision
meansinformationtransferatadistance.“Datacommunicationreferstotheexchange
ofmeaningfuldatabetweentwodevicesconnectedviasomeformofwiredorwireless
transmissionmedium.Itincludethetransferofdata,themethodoftransferand
preservationofdataduringthetransferprocess”.Fordatacommunicationtooccur,the
communicatingdevicesmustbepartofdatacommunicationsystem,whichismadeupof
combinationofphysicalequipments(Hardware)andprograms(software).
Theeffectivenessofdatacommunicationdependsonfourfundamental
characteristics:ReliableDelivery,Accuracy,Timeliness&Jitter.
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11. Basic Concepts
EffectivenessofDataCommunication:-
1.ReliableDelivery:-Datasentfromsourceacrossthecommunicationsystemmustbe
deliveredonlytocorrectdestinationi.e.Datamustreceivedbytheintendeddeviceor
userandonlybythatdeviceoruser.i.e.Thesystemmustdeliverthedatatocorrect
destination.
2.Accuracy:-Datamustbedeliveredatdestinationaccuratelyi.e.withoutanyalteration.
Ifdataischangedoralteredduringitstransmissionitmaybecomeunusable.i.e.The
systemmustdeliverdataaccurately.
3.TimelinessDelivery:-Datamustbedeliverinatimelymanner.Otherwise,itmaybe
uselessforthereceiver.Incaseofaudio,videoandvoicedatatimelydeliverymeans,
deliveringdataastheyareproduced,insameorderthattheyareproducedandwithout
anysignificantdelay.Thiskindofdeliveryiscalledreal-timetransmission.i.e.The
systemmustdeliverdataintimelymanner.
4.Jitter:-Itreferstothevariationinthepacketarrivaltime.“Itisunevendelayinthe
deliveryofaudioorvideopackets.”EgIfvideopacketsaresentevery30ms,some
arrivewith30msdelayandotherwith40msdelay,itresultthepoorqualityofvideo.
Sopacketsmustbedeliveredandreceivedatconstantrate.
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12. Basic Concepts
ComponentsofDatacommunication:-
Adatacommunicationsystemismadeupoffivebasiccomponents:Message,Sender,
Receiver,Medium&Protocol
1.Message:-Itisdata/informationtobecommunicated.Itcanbeeithertext,
numbers,audio,videooranycombinationofthesetypes.
2.Sender:-Itisthedevicethatsendthedatamessage.Itcanbeacomputer,work
station,telephone,videocameraetc.
3.Receiver:-Itisthedevicethatreceivethemessage.Itcanbecomputer,workstation,
telephone,televisionetc.
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Rule:1
Rule:2
Rule:n
Rule:1
Rule:2
Rule:n

13. Basic Concepts
ComponentsofDatacommunication:-
Adatacommunicationsystemismadeupoffivebasiccomponents:Message,Sender,
Receiver,Medium&Protocol
4.TransmissionMedium:-Itisthephysicalpathbywhichmessagetravelsfrom
sendertoreceiver.Itcanbeatwisted–paircable,co-axialcable,fiberopticcable,
radiowaveetc.
5.Protocol:-Itissetofrulesthatgovernthedatacommunicationfromsenderto
receiver,withoutprotocol,twodevicesmaybeconnectedandtransmitdatabutcan
notcommunicateeg.OneSpeakHindi&anotherspeakFrench 13
S.P. Chauhan
Rule:1
Rule:2
Rule:n
Rule:1
Rule:2
Rule:n

14. Basic Concepts
ComponentsofDataCommunication:-
Thepurposeofcommunicationbetweentheapplicationentitiesisnotjustservedby
exchangingbits.Thecommunicationneedstobemeaningful.Meaningful
communicationisalwaysdonewithapurposeandaimsatenlargingcommon
understandingbetweencommunicatingentities,whichiscalledprotocol.Sophysical
transferofbitsistransmissionbutnotcommunication.
Howeverbothcommunicationandtransmissiondealwiththeexchangeofbits/data/
information.Butafewdifferencebetweenthemarelistedbelow:
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S. No. Communication Transmission
1.Itreferstotheexchangeof
meaningfulinformationbetween
twocommunicatingdevices
Itreferstothephysical
movementofinformation
2.Itisatwowayscheme Itisonewayscheme

15. Basic Concepts
DataRepresentation:-
Datacanbeavailableinvariousformssuchastext,numbers,images,audioandvideo.In
networkingdatahastobetransmittedfromsourcetodestinationinbinaryform.Thus
informationrepresentedusingalphabets(a–z,A–Z),numbers(0,1,2---------9),special
symbols(!,@,#,----)andimageshastobeconvertedintosequenceofbits0&1.Audio
&videodatahavetobeconvertedfromdigitaltoanalogsignalandviceversafor
transmissionwiththehelpofdifferentencodingschemes.
Soinsteadofusingsinglebinarybits,agroupofbitsisusedasacodetorepresenta
symbol.Thenumberofbitsusedpercodewordwilldependonthetotalnumberof
symbolstoberepresented.Eg.If5bitsareusedpercodewordthen2
5
=32combinations
wouldbepossible.Ifcodewordlengthisincreaseto8then,thenumberofcombinations
wouldbe2
8
=256,hence8bitcodecanrepresent256symbols.Asetofsuchcodeword
iscalledcodeset.Thesecodesetsareverycommonlyusedforthedatarepresentation.
ThevariouscodingschemesareUnicode,ASCII(AmericanStandardCodeFor
InformationInterchange),ExtendedASCII,EBCDIC,[ExtendedBinarycodeddecimal
Interchangecode].
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16. Basic Concepts
ACommunicationsModel:-
DTE: Data Terminal Equipment & DCE:Data Communication Equipment
DTE(DataTerminalEquipment):-
Itisaterminalresidingatphysicallayerorcanbeanythingthatcouldbeableto
generatetoconsumedigitaldatalikecomputer.i.e.DTEisanydevicethatfunctions
eitherasaserviceoforasdestinationforbinarydigitaldata.Itcanbe:
Terminal,Microcomputer,Computer,PrinteroraFaxmachineoranyother
devicethatgenerateorconsumeadigitaldata.Eg:Phone,tabandcomputer.
Inotherwords,itisanassemblythatoperateseitherasasourceoforasa
destinationforbinarydigitaldata.
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S.P. ChauhanTransmission
Network
DTE DTEDCE DCE

17. Basic Concepts
DTE (Data Terminal Equipment):-
ThereisnodirectmechanismforDTEtocommunicate,socommunicationtakesplace
throughsomeintermediarydevicesi.e.DTEdon’tcommunicatedirectlywithone
another,theygenerateandconsumeinformationbutneedanintermediaryto
communicate.
Example:AmobilephoneconnectwithsmartTV.Itwillnotconnectdirectlywith
DTE.Itneedssomecableoranyothercomponent(H/WorS/W).
Eg:SupposeyourbrainisaDTEdevicewhichcangenerateandconsumeideas.Ifyour
brainwantstocommunicatewithyourfriend’sbraintointerprettheideagenerated
byyourbrain,Itwouldnotbepracticallypossible.Consequently,yourbrainwilltake
helpofyourvocalchordsfortheinterpretationoftheidea.That’showaDTEworks.
DCE(DataCommunicationEquipment):-Itinvolvesoperativeunitsthattransferorreceives
dataintheformofdigitaloranalogsignalwithinanetwork.Inthephysicallayer,the
DCEobtainthedataproducedbytheDTEandconvertittosuitablesignals.Thenit
introducethesignalontothetelecommunicationlink.Generally,theDCE’sweuseat
thislayerinvolvesmodems(modulator/demodulator).
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18. DCE(DataCommunicationEquipment):-
thetransmissionmediumandsendsthetranslatedsignaltoanotherDCEonthe
network.ThesecondDCEextractsthesignaloutoftheline,andtransformsitinto
suchaformthatitsDTEcanuseordeliver.
Inordertoachievethiscommunication,boththesendingandreceivingDCEsmust
usethesamemodulatingmethod(e.g.Frequency-shiftkeying(FSK)itisaamethod
oftransmittingdigitaldatabyshiftingthefrequencyofacarriersignaltorepresent
binary1sand0sandiscommonlyusedovertelephonelinesforcallerID(displaying
callers'numbersandremotemeteringapplications),eg.ifyouwanttocommunicate
tosomeonewhounderstandsoneparticularlanguage,thenyoumustspeakthe
particularlanguage.
ThereisnocompulsiontosynchronizethetwoDTEswitheachother,buteachmust
becoordinatedwithitsownDCE,andtheDCEsmustbecoordinatedsothatdata
translationoccurswithoutlossofintegrity.
Basic Concepts
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Inanetwork,aDTEproducesdigitaldataand
movethemtoaDCE.ThenDCEtranslatesthe
datainaspecificformthatcanbeacceptedby

19. Basic Concepts
Simplified Communications Model:-
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20. Basic Concepts
TransmissionMode/ModesofDataTransmission/DirectionofDataFlow/Typesof
Communication:-Thetransmissionmodeexplainshowthedataflowwilloccurbetween
twoconnecteddevices.Itcanbesetbycommunicationsoftware.
Thetermtransmissionmodeisusedtodefinethedirectionofdataflowbetweentwo
linkeddevices.Therecanbethreetypesoftransmissionorcommunicationbetweentwo
devices.Simplex,HalfDuplex&FullDuplex.
i.Simplex:-(Unidirectionali.e.onetransmitsandotherreceives)
Inthismodecommunicationisunidirectionali.e.onlyoneofthetwocommunicating
devicestransmitinformation,howeverothercanonlyreceiveit.Sosimplextransmission
sendsdatainonedirectiononly.Eg.Televisiontransmission:assatelliteonlytransmitsthe
datatotelevision,viceversaisnotpossible.Insimplexwecannotsendamessagebackto
thesenderi.e.wejustneedtosendacommand/signal,anddonotexpectanyresponse
back.ThecommunicationfromCPUtotraditionalmonitororkeyboardtoCPUis
unidirectionali.e.Keyboards&traditionalmonitorsareexamplesofsimplexdevices.
Thismodecanuseentirecapacityofchanneltosenddatainonedirectiononly.
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21. Basic Concepts
TransmissionMode/ModesofDataTransmission/DirectionofDataFlow/Typesof
Communication:-
ii.HalfDuplex:-(Thesesystemsarebidirectionali.e.theycantransmitaswellasreceive
butnotsimultaneously)
Inthistransmissiondatacanbetransmittedinbothdirectionsonasignalcarrieror
path,butnotatthesametime.Sohalf-duplextransmissionsendsdataineitherdirection,
butonlyonewayatatime.i.e.Inthistransmissionmodebothcommunicatingdevice
canreceiveandtransmitdata/informationbutnotatsametime.Whenonedeviceis
sending,theothercanonlyreceiveatthatpointoftime&viceversaeg.Walkie-Talkie
usedbypolice&armypersonals.
Inthistransmissionmode,theentirecapacityoftransmissionmediumistakenover
bythedevice,whichistransmitting(sending)atthatmoment.
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22. Basic Concepts
TransmissionMode/ModesofDataTransmission/DirectionofDataFlow/Typesof
Communication:-:-
iii.FullDuplex:-(Thesesystemsaretrulybidirectionalastheycantransmitaswellas
receivesimultaneouslyi.e.theyallowthecommunicationtotakeplaceinboth
directionssimultaneously.)
Inthistransmissiondatacanbesendinboththedirectionssimultaneouslyasitis
bidirectional.Sofull-duplextransmissionallowstransmissioninbothdirectionatonce.i.e.
Inthistransmissionmodebothcommunicatingdevicescantransmitandreceivedata
simultaneouslyeg.Telephonenetwork.Asbothpeoplecantalk&listenatthesametime
Infullduplexmode,thesignalsgoingineitherdirectionsharethecapacityoflink.This
sharingcanbeoccurintwoways.Eitherlinkmustcontaintwophysicallyseparate
transmissionpath(oneforsending&otherforreceiving)orthecapacityofchannelis
dividedbetweensignalstravellinginbothdirections.Manynetworksprovideatleasttwo
logicalchannelsperconnectiononeforthenormaldataandotherforurgentdata.
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23. Basic Concepts
Differencesb/wSimplex,Half-duplexandFull-duplexmode:-
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Basis for
comparison
Simplex mode Half-duplex mode Full-duplex mode
Direction of
communication
In simplex mode, the
communication is
unidirectional.
In half-duplex mode, the
communication is
bidirectional, but one at a
time.
In full-duplex mode, the
communication is bidirectional.
Send/ReceiveA device can only send the
data but cannot receive it or
it can only receive the data
but cannot send it.
Both the devices can send
and receive the data, but
one at a time.
Both the devices can send and
receive the data simultaneously
i.e. at same time.
PerformanceThe performance of simplex
mode is not better than the
half-duplex mode
The performance of half-
duplex mode is not better
than the full-duplex.
The Full-duplex mode has better
performance among simplex and
half-duplex mode as it doubles
the utilization of the capacity of
the communication channel.
Example Examples of Simplex mode
are Radio, Keyboard,
Traditional Monitor & TV.
Example of half-duplex is
Walkie-Talkies.
Example of the Full-duplex mode
is a telephone network.

24. Basic Concepts
DataTransmission:-
Datatransmissionmeansmovementofdatawhichisintheformofbitsbetween
twoormorecommunicatingdevice.Datatransmissiontakesplaceoversome
mediumformonedevicetoanother.Therearetwowaysoftransmittingthebits:
i.ParallelTransmission
ii.SerialTransmission
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Data Transmission
SynchronousAsynchronous
Serial TransmissionParallel Transmission

25. Basic Concepts
DataTransmission:-
i.ParallelTransmission:-Inparalleltransmissionofdata,allthebitsofabyte/code
wordaretransmittedsimultaneouslyonseparatewiresasshowninfig.
2.Inparalleltransmissiontheclockfrequencycanbekeptlowwithout
affectingthespeedofoperation.
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S.P. Chauhan
Thistypeoftransmissionrequiremultiple
circuitsforinterconnectingthetwodevices.
Paralleltransmissionispossiblepracticallyifthe
twodevicesareclosetoeachother.Eg.Parallel
transmissiontakesplacebetweenacomputer&
printer.
Advantages:-
1.Inparalleltransmissionallthedatabitsare
transmittedsimultaneously.Sothetime
requiredforthetransmissionofN–bit
wordisonlyoneclockcycle.

26. Basic Concepts
DataTransmission:-
i.ParallelTransmission:-
Disadvantages:-
1.Totransmitn–bitword,weneedNnumberofwires.
2.Withincreaseinthenumberofusers,thesewireswillincreasetoan
unmanageablenumbers.
ii.SerialTransmission:-Inserialtransmission,thebitsofabyte/codewordare
transmittedoneaftertheanotherasshowninfig.
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27. Basic Concepts
DataTransmission:-
ii.SerialTransmission:-
Thebytestobetransmittedfirststoredinshiftregister.Thenthesebitsareshifted
fromMSBtoLSBbitbybitinsynchronizationwiththeclock.Thebitwhichfallout
oftheshiftregisteristransmitted.Forserialtransmissiononlyonewireisneeded
betweenthetransmitter&thereceiver.Henceitispreferredforlongdistancedata
communication.
Asonlyonebitistransmittedperclockcycle,itrequiresatimecorrespondingto8–
clockcyclestotransmitonebytewhereasparalleltransmissionrequireonlyone
clockcycletotransmitabyte.Butinserialtransmissiontimecanbereducedby
increasingtheclockfrequency.
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28. Basic Concepts
DataTransmission:-
ii.SerialTransmission:-Thefigshowsthepracticalserialtransmissionsystem.The
receiver&transmitterbotharecomputers.Ascommunicationwithinacomputeris
Advantages:-
1.Onlyonewireisrequired,forconnectingthetransmittertothereceiver.So
practically,theserialtransmissionisalwayspreferred.
2.Reductionofcostduetolessnumberofwires/conductors.
Disadvantages:-
1.Thespeedofdatatransferislow.
2.Toincreasethespeedofdatatransfer,itisnecessarytoincreasetheclock
frequency.
Serialtransmissionisusedforcomputertocomputercommunication,speciallyfor
longdistancecommunication
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parallel,itisnecessarytoconvertthe
paralleldataintoserialatthetransmitter.
Atreceiver,theserialtoparallel
conversionisrequiredtobeperformed.

29. Basic Concepts
DataTransmission:-
DifferenceBetweenParallelTransmission&SerialTransmission:-
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S.P. Chauhan
S. No.Parameter ParallelTransmission Serial Transmission
1.
Number of wires required
to transmitN bits
N wires 1 wire
2.
Number of bits transmitted
simultaneously
N bits 1 bit
3.Speed of data transferFast Slow
4.Cost
Higherdue to more number
of conductors
Low, as only one wire
is used
5.Application
Short distance
communication such as
computer to printer
communication
Long distance
computer to computer
communication

30. Basic Concepts
TypesofSerialTransmission:-Asshownearliertherearetwomethodsofserial
transmissionAsynchronousdatatransmission&Synchronousdatatransmission.
1.AsynchronousDataTransmission:-Inasynchronousdatatransmissionthe
transmittercantransmitthedatabyteatanyinstantoftimebutonlyonebyteis
sentatatime.Aftersendingonebyte,thenextbytecanbesentafteranarbitrary
timedelayasshowninfig.
Thereceiver&transmitteroperatesatdifferentclockfrequencies.Asthedata
transmissioncanoccuratanyinstantsoitbecomedifficultforthereceiverto
understandtheinstantatwhichtimethebytehasbeentransmitted.
SotohelpreceivertoreceivethedatabytesStart&Stopbitsareusedalongwith
eachdatabytes.Thestartbitisalways0&stopbitisalways1.
Theidletimebetweentwodatabytesisnotconstant.Thisidletimeisalsocalled
thegapsbetweenthedatabytes.
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31. Types of Serial Transmission
1.AsynchronousDataTransmission:-
Themechanismdiscussedearlieriscalledasynchronousbecauseatbytelevel,the
sender&receiverdonothavetobesynchronized.
Butwithineachbyte,thereceivershouldstillbesynchronizedwiththeincomingbit
stream.i.e.synchronizationisrequiredonlyforthedurationofsinglebyte.
Followingfigshowstheblockdiagramofsynchronoustransmission.
Above fig shows that start bit is 0 & stop bit is 1.
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32. Types of Serial Transmission
1.AsynchronousDataTransmission:-
Disadvantages:-
i.Additionbitscalledstart&stopbitsarerequiredtobeused.
ii.Theuseofstart&stopbitsandgapsbetweenthedataunitsmakesthe
asynchronoustransmissionslow.
iii.Timingerrorcantakesplace.
Advantages:-
i.Synchronizationbetweentransmitter&receiverisnotnecessary.
ii.Itispossibletotransmitsignalfromthesourcehavingdifferentbitrates.
iii.Thismodeoftransmissioniseasytoimplement.
iv.Itisaneffectivescheme
Theconnectionofakeyboardtoacomputerisanexampleofasynchronous
transmission.
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33. Types of Serial Transmission
2.SynchronousDataTransmission:-Itiscarriedoutunderthecontrolofmasterclock.
Inthistransmission,thebitswhicharetobeingtransmittedaresynchronizedtoa
referenceclock.Nostart&stopbitsareusedbutthebytesaretransmittedasablock
inacontinuousstreamofbitsasshowninfig.
Inthistransmissionthereceiveroperatesexactlyatthesameclockfrequencyasthat
oftransmitter.
Flagisasequenceoffixednumberofbitswhichisprefixedtoeachblock.Itisuseful
toidentifythestartofblock.
Insynchronoustransmissionthebitstreamtobetransmittediscombinedinto
longerframe,whichmaycontainmorethanonebyte.
Thereceiverseparatesthebitstreamintobytesforthepurposeofdecoding.Start&
stopbitsarenotusedbutbitsaretransmittedseriallyoneaftertheother.
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34. Types of Serial Transmission
2.SynchronousDataTransmission:-Fig.showstheblockdiagramofsynchronous
transmission.
Advantages:-
i.Themainadvantageisspeed.Thespeedoftransmissionismuchhigherthan
thatofasynchronoustransmission.
ii.Absenceofstart&stopbits.
iii.Absenceofgaps.
iv.Timingerrorsarereducedduetosynchronization.
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Here we can see the absence
of start / stop bits and gaps

35. Types of Serial Transmission
2.SynchronousDataTransmission:-
Disadvantages:-
i.Timingisveryimportant.Theaccuracyofdataisdependentirelyonthe
abilityofthereceivertocountthereceivedbitsaccurately.
ii.Thetransmitter&receiverhavetooperateatthesamefrequency.This
requirepropersynchronizationwhichmakesthesystemcomplicated.
Thesynchronoustransmissionduetoitshighspeedisusefulforthe
transmissionofdatafromonecomputertoother.
Thebytesynchronizationisaccomplishedbythedatalinklayerwhen
synchronoustransmissionisusedbetweencomputers.
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36. Types of Serial Transmission
ComparisonofAsynchronous&SynchronousDataTransmission:-
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S. No.Parameter Asynchronous TransmissionSynchronous Transmission
1.Synchronization Not Needed Needed
2.Start& Stop Bits Used Not Needed
3.Gapbetween data blocksPresent Not Present
4.Speed Low High
5.Application
Communication between
computer & keyboard
Communication between
two computers

37. Basic Concepts
ComputerNetwork:-
Nowadaysthemostimportanttechnologyhasbeeninformationgathering,its
processinganddistribution.Thecomputerandcommunicationhavebeenmerged
togetherandtheirmergerhashadagreatimpactonthemannerinwhichcomputer
systemareorganized.Theconceptofthe“computercenter”asaroomwithalarge
computertowhichuserbringtheirworkforprocessingisnowtotallyobsolete.
Theoldmodelinwhichsinglecomputerusedtoserveallcomputational
requirementsofanorganizationhasbeenreplacedbyanewone“Inwhichalargeno.
ofseparatebutinterconnectedcomputerperformthejob.Suchsystemsarecalled
computernetworks.”
ComputerNetworksmaybedefinedasacollectionofautonomouscomputers
interconnectedbysingletechnology.i.e.ComputerNetworkisaninterconnected
collectionofagroupoftwoormoreautonomouscomputerwhichareconnectedtogether
toshareinformationandresources.
37
S.P. Chauhan

38. Basic Concepts
ComputerNetwork:-
Computers/resourcesaresaidtobeinterconnectediftheyarecapableof
exchangingdatawitheachother.Theconnectionbetweentheseparatecomputers
canbedoneviaacopperwire,fiberoptics,microwaveorcommunicationsatellite.
Hereautonomousmeans,thereisnomasterandslaverelationshipandallthe
computersareequalandfreetoactindependently.Normallyeachcomputerhasits
ownoperatingsystemwhichisbasicallyanetworkoperatingsystem.Ausermust
explicitlyconnecttoothercomputersinordertocommunicatewiththem.
Computernetworkmayalsodefinedasthecollectionseveralcomputingmachines,
peripheraldevicesandstoragedeviceswhichareconnectedtogethertoshare
informationandresources.
Linkconnectingthedevicesareoftencalledcommunicationchannels.Mostnetwork
usedistributedprocessing.
38
S.P. Chauhan

39. Basic Concepts
DistributedProcessing:-
ComputerNetworkusesdistributedprocessing.Indistributedprocessingtaskis
dividedamongseveralcomputersi.e.multipleindividualcentralprocessingunits
(CPU)workonthesameprograms/functionsorsystems.Instead,asinglecomputer
handlesanentiretask,eachseparatecomputerhandlesasubsetormodules.i.e.the
useofmorethanoneprocessortoperformtheprocessingforanindividualtask.Itis
alsoknownasparallelprocessing,inwhichprogramsarerunmorequicklywith
multipleprocessors.
Itistheprocessinginwhichtaskisdividedamongmultiplecomputers.Insteadofasingle
largemachinebeingresponsibleforallaspectofaprocess,eachseparatecomputer
handlesasubset.
Ifonecomputercanforciblystart,stoporcontrolanother,computerarenot
autonomous.Asystemwithonecontrolunitandmanyslavesoralargecomputers
withremoteprintersandterminalsiscalleddistributedsystem.
39
S.P. Chauhan

40. Basic Concepts
DistributedProcessing:-Indistributedsystemtheexistenceofmultipleautonomous
computerisnotvisibletotheuser.Theusercantypeacommandtorunaprogramandit
runs.Itisuptotheoperatingsystemtoselectthebestprocessor,findandtransport
relatedinputfilestothatprocessorandgiveresulttouser.Withadistributedsystem,
nothinghastobedoneexplicitly,itisallautomaticallydonebythesystemwithoutthe
user’sknowledge.Sobasicallyadistributedsystemisasoftwaresystembuiltontopofa
network.
ComputerNetworkv/sDistributedSystem:-Internetisnotasinglenetworkbutanetwork
ofnetworksandWebisadistributedsystemthatrunsontopoftheInternet.
Thekeydistinctionisthatinadistributedsystem,acollectionofcomputersappearstoits
usersasasinglesequentialsystem.Alayerofsoftwareonthetopoftheoperating
system,calledmiddleware,isresponsibleforimplementingthismodel.Awellknown
exampleofadistributedsystemistheWorldWideWeb,inwhicheverythinglookslikea
document(Webpage).
Nevertheless,thereisconsiderableoverlapbetweenthesetwo.Eg.Bothdistributed
system&computernetworkneedstomovethefilesaround.Thedifferencelieswho
invokethemovement,theuserorthesystem.
40
S.P. Chauhan

41. Basic Concepts
AdvantagesofDistributedProcessing:-
1.Security/encapsulation:-Asystemdesignercanlimitthekindofinteractionthata
givenusercanhavewithentiresystemeg.Abankcanallowuserstoaccesstheir
ownaccountthroughATMwithoutallowingtoaccessbank’sentiredatabase.
2.DistributedDatabase:-Noonesystemneedstoprovidestoragecapacityforentire
databaseeg.worldwidewebgivesaccesstoinformationthatmaybeactuallystored
manipulatedanywhereontheinternet.
3.SecuritythroughRedundancy:-Multiplecomputersrunningthesameprogramat
thesametimecanprovidesecuritythroughredundancyeg.Inspaceshuttlethreeor
morecomputersrunthesameprogram,sothatifonehasH/WorS/Werror,the
othercanoverrideit.
4.FasterProblemSolving:-Multiplecomputersworkingonpartsofaproblem
concurrentlycansolveproblemfasterthenasinglemachineworkingalone.
41
S.P. Chauhan

42. Basic Concepts
PrinciplesofComputerNetwork:-
Thebasicprinciplesofcomputernetworkareasfollows:-
1.Thecomputernetworkmustprovideadvancedservices,greaterscalabilityi.e.
capacitytochangethesize/scaleandbettersecurity.
2.Everycomputeronthenetworkmusthavesoftwarethatsupportsthemovementof
informationinandoutofthecomputer.Eg.Modemsoftwareand/oranetwork
operatingsystemmustbepresentoneverycomputer.
3.Allcomputeronthenetworkmusthaveanetworkcardthatprovidetheentranceor
doorwayinthatcomputerforinformationtraffictoandfromothercomputer.
4.Anetworkusuallyhaveatleastoneconnectingdevice,likeahuborarouterthat
tiesthecomputersonthenetworktogetherandactasaswitchboardforpassing
message.
5.Theremustbecommunicationmedialikecablesorradiowavesconnectingnetwork
devices.
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S.P. Chauhan

43. Basic Concepts
AttributesofComputerNetwork:-Thecomputernetworkscomeinallsizesfromtwo
computersconnectedtoshareaprinterorconnectedtotheInternet,whichoneofthe
largestnetworkthatjoinsmillionsofcomputersofallkindsallovertheworld.The
differentattributesofcomputernetworkaredescribedasfollows:-
1.MinimumHumanSupervision:-Inmostnetworks,oneorbothendpoints,aswellas
allintermediatepoints,involvedinagivencommunicationmaybemachineswith
onlyminimalhumansupervisioni.e.theymustbeautomated.
2.Anonymity:-Thecomputernetworkremovesmostofthethings,suchasappearance,
voiceorcontext,bywhichwerecognizeothers.
3.DynamicRouting:-Routingbetweentwoendpointsareusuallydynamictomaintain
orimprovereliabilityandperformance.
4.Distance:-Theendpointsofmostnetworksarephysicallyfarapartbutthespeedof
communicationisfastenoughthathumanusuallycannottellwhetheraremotesite
isnearorfar.
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S.P. Chauhan

44. Basic Concepts
BasicComponentsofComputerNetwork:-Therearemanywaysforcomputernetwork
tobesetupandestablishedinvolvingvariousmediums,hardwareandnetworklayout.
Thebasiccomponentsofacomputernetworkthatareusedtotransmitthemessageare
asfollows:-
1.Message:-Itisdata/informationtobecommunicated.Itcanbeeithertext,
numbers,audio,videooranycombinationofthesetypes.
2.Sender:-Itisthedevicethatsendthedatamessage.Itcanbeacomputer,work
station,telephone,videocameraetc.
3.Receiver:-Itisthedevicethatreceiversthemessage.Itcanbecomputer,
workstation,telephone,televisionetc.
4.CommunicationLink/TransmissionMedium:-Itisthephysicalpathbywhich
messagetravelsfromsendertoreceiver.Itcanbeatwisted–paircable,co-axial
cable,fiberopticcable,radiowaveetc.
5.Modem:-Itisadevicethatconvertsadigitalsignaltoananalogsignalandvice
versa.Themodemstandsformodulator/demodulator.
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S.P. Chauhan

45. Basic Concepts
BasicComponentsofComputerNetwork:-
6.Protocol:-Thesystemsconnectedtothecommunicationlinkmustfollowasetof
communicationrulesfordatatoarriveatitsintendeddestinationandforthe
sendingandreceivingsystemstounderstandeachother.Itissetofrulesthat
governthedatacommunicationfromsendertoreceiver,withoutprotocol,two
devicesmaybeconnectedbutcannotcommunicateeg.OneSpeakHindi&another
speakFrench
7.NetworkOperatingSystem(NOS):-Itisrequiredforthecomputerconnectedtothe
network.
8.NetworkInterfaceCard(NIC):-Itisrequiredforthecomputerwhicharenotready
tobeusedinanetwork.
45
S.P. Chauhan

46. Basic Concepts
ComputerNetworkCriteria:-Ascomputernetworkisasystemwhichallows
communicationamongthecomputersconnectedinthenetwork.Sotoprovide
effectivedatacommunication,anetworkmustmeetacertainnumberofcriteria,
someofwhichareasfollows:Performance,ReliabilityandSecurity.
1.Performance:-Itcanbedeterminedbyconsideringsomeofthefactorssuchas:
a.TransitTime:-Itistheamountoftimerequiredbyamessagetotravelformone
devicetoanother.
b.ResponseTime:-Itistheelapsedtimebetweentheuserinitiatesarequestand
thesystemstartrespondingtothisrequest.i.e.timeelapsedbetweenenquiryand
response.
c.Throughput:-Itistheamountofworkdoneinaunittime.Toachievegreater
performance.Weneedtoimprovethroughputandreducetransitandresponse
time.Butincreasingthroughputbysendingmoredatatonetworkoftenleadsto
trafficcongestioninthenetworkandthusincreasesthedelay.Theotherfactors
decidingperformanceare:
d.Numberofusers:-Havinglargenumberofconcurrentuserscanslowtheresponse
timeinanetwork,whichisnotdesigntocoordinateheavytrafficload. 46
S.P. Chauhan

47. Basic Concepts
ComputerNetworkCriteria:-
1.Performance:-Itcanbedeterminedbyconsideringsomeofthefactorssuchas:
e.Typesoftransmissionmedium:-Themediumdefinesthespeedatwhichdata
cantravelthroughaconnection(datarate).
f.CapabilityofconnectedH/W:-Thetypesofhardwareincludedinanetworkaffect
boththespeedandthecapacityoftransmission.Ahigher-speedcomputerwith
greaterstoragecapacityprovidesbetterperformance.
g.EfficiencyofSoftware:-Thesoftwareusedtoprocessthedataatthesender,
receiverandintermediatenodesalsoaffectsnetworkperformance.
2.Reliability:-Reliabilityofanetworkcanbedeterminedbythefactorssuchashow
frequentlythefailureisoccurringandhowmuchtimeisbeingspentinrecovering
fromalinkfailure.
3.Catastrophe:-Networkmustbeprotectedfromcatastrophiceventssuchasfire,
earthquake,ortheft.
4.Security:-Thenetworksecurityreferstoprotectionofdatafromunauthorizeduser
oraccessandviruses.Inaddition,theremustbeproceduresandpoliciestohandle
theftandrecoveryofdata.
47
S.P. Chauhan

48. Basic Concepts
AdvantagesofcomputerNetwork:-
1.SharingInformation:-Itisoneofthemostimportantadvantageofcomputer
network.Intheabsenceofnetwork,transferringofinformationfromonecomputer
toanotherrequirestheuseofCD,Pendriveetc.Computernetworksolvethis
problem,asthecomputersconnectedtonetworkcansharetheinformation,ifthey
areinthesamebuildingorevenwhentheyarelocatedgeographicallyapart.Eg.
Whenweconnecttointernetandopenawebsiteonourcomputer.
2.SharingHardwareResources:-Anetworkfacilitatessharingofhardwareresources
inaneffectiveanduserfriendlymanner.Whencomputersareconnectedtoa
network,theycanshareperipheralssuchasprintersanddiskdriveswithany
computer.Eginanofficehavingfivetotencomputersandoneprinter.
3.SharingSoftwareResources:-Softwareresourcesaretheprogramsorapplications
thatareusedbythecomputertoperformanyusefulfunctionortocarryoutdaily
basistask.Inanenvironmentwherenetworkisnotavailable,userswillhaveto
installandconfigureanyapplicationthattheyneedindividually.However,ifthe
computersareconnectedviaanetworktherequiredsoftwareorapplicationcanbe
installedandconfiguredcentrallyonaserverandsharedbyall.Thissavesthe
valuabletimeanddiskspace. 48
S.P. Chauhan

49. Basic Concepts
AdvantagesofcomputerNetwork:-
4.PreserveInformation:-Anetworkedenvironmenthelpstopreserveinformationas
well.Itisdifficulttomaintainregularbackupsofdataonanumberofstandalone
computersandwithoutbackupimportantdatacanbelostincaseofsomeaccident
orfailureofcomputer.However,inanetworkenvironment,acopyoftheimportant
datacanbekeptontheserveraswellasonotherconnectedcomputeronthe
network.Inthiscasefailureofonecomputerwillnotresultinlossofinformationas
datacanstillbeaccessedfromothercomputerswheneverrequired.
5.Communications:-Acomputernetworkcanprovideapowerfulcommunication
mediumamongwidelyseparatedpeoples.Usinganetworkitiseasyfortwoormore
peoplewholivefaraparttowriteareporttogether,i.e.whenonepersonmakesa
changetothedocument,whichiskeptonline,theotherscanseethechange
immediately,insteadofwaitingseveraldaysforalater.
49
S.P. Chauhan

50. Basic Concepts
NeedofComputerNetwork:-
1.Toprovidesharingofresourcessuchasinformationorprocessors.
2.Toprovideinter-processcommunicationamongusersandprocessors.
3.Toprovidedistributionofprocessingfunction.
4.Toprovidecentralizedcontrolforageographicallydistributedsystem.
5.Toprovidecentralizedmanagementandallocationofnetworkresources.
6.Toprovidecompatibilityofdissimilarequipmentandsoftware.
7.Toprovidenetworkuserswithmaximumperformanceatminimumcost.
8.Toprovideanefficientmeansoftransportlargevolumesofdataamongremote
locations.
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S.P. Chauhan

51. Basic Concepts
DisadvantagesofComputerNetwork:-Someofthecommondisadvantagesofthe
computernetworkareasfollows:-
1.Expensive:-Thefirstandtheforemostdisadvantageofcomputernetworksisthat
theyareexpensivetopurchaseandmaintain.Thecablingandinstallationofalarge
sizedcomputernetworkisverycostly.
2.DataSecurity:-Thespecialsecuritymeasuresareneededtostopusersfromusing
programsanddatathattheyshouldnothaveaccessto.Theproperpermissionmust
beissuedtovarioususersaccordingtothenatureofwork.Henceproperpassword
validationcheckmustbeappliedfortheauthorization&authentication.
3.ManageDependence:-Thecomplexnetworksrequireanetworkmanagertokeepit
running.Themajorproblemwiththenetworkisthattheirefficiencyisverydepend
ontheskillifthenetworkmanager.Abadlymanagednetworkmayoperateless
efficientlythannon-networkedcomputers.
4.VulnerabletoHackers&Viruses:-Thecomputernetworksareveryvulnerableto
hackers&viruses.Eg.Ifanetworkispoorlyimplemented,improper
communicationmaytakeplace.Thismayresultinlossofprivacyorcorrupt
informationsystem.Secondlythevirusononesysteminanetworkcanaffectthe
wholecomputernetwork.
51
S.P. Chauhan

52. Basic Concepts
ComputerNetworkArchitecture/Model:-Itspecifieshowthephysical&logical
componentsofcomputernetworkareassembledandconnectedwitheachotherto
facilitateinformationexchangeandresourcesharingtwomajortypesofcomputer
architectureareclient/server&peer-to-peer.
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S.P. Chauhan
1.ClientserverArchitecture/Model:-Inthis
architectureeachcomputeriseitheraclientor
server.i.e.Inthisarchitecture,atleastone
computerisdesignatedasaserver;whichisa
centralcomputerinthenetworkthatprovides
servicestotheclients.Aclientisamachinethat
requestsomethingfromanothercomputer.Soto
completeaparticulartaskthereexistsa
centralizedpowerfullhostcomputerknownas
serveranduser’sindividualworkstationas
clientasshowninfig.

53. Basic Concepts
ComputerNetworkArchitecture/Model:-
Butdisadvantageofthisarchitectureisthatwithtimeasnumberofclients
increases,thenumberofrequeststoserveralsoincreases,sowemightneedmore
thanoneservertoservelargenumberofrequests.
53
S.P. Chauhan
1.ClientserverArchitecture/Model:-
Clientrequestforservicefromserverandserver
respondbyprovidingthatservice.Butnoclient
cancommunicatedirectlywitheachotherinthis
architecture.Exampleofclient/serverarchitecture
isaccessingwebsitefromhomewiththehelpof
browser.
Anadvantageofclient/serverarchitectureisthat
theIPaddressoftheserverisalwaysfixedand
serverisalwaysavailableonthenetworkfor
clients.

54. Basic Concepts
ComputerNetworkArchitecture/Model:-
2.Peer-to-Peer(P2P)Architecture/Model:-Thisarchitecturedoesnotrelyondedicated
serversforcommunication,butcomputerssimplyconnectedwitheachotherinawork
grouptosharefilesandperipheraldevices.i.e.itusesdirectconnectionsbetween
clients(peers)asshowninfig.soallcomputershavesamestatus,hencethetermpeer
isused.
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S.P. Chauhan
InP2Peverynodeisabletoinitiateorcomplete
anysupportedtransaction/FileTransferwith
theotherconnectednodeandeverynodecan
directlycommunicatewithanother.Theupper
limitofnodesinP2Pisbetween10to25.If
therearemorenodesthenaP2Pmachinecan
beusedasdedicatedserver.Theadvantageof
P2Pnetworkisthatmillionsofnodecanbe
connectedtothenetworkstocontribute
resourcesirrespectiveofthedifferenceintheir
localconfiguration.Buthighlydecentralized
approachofP2Parchitecturecanbetoughto
manage.

55. Basic Concepts
ComputerNetworkArchitecture/Model:-
WhentousePeer-to-Peer(P2P)Architecture/Model:-Thepeertopeernetworksare
suitableforthefollowingconditions:
1.Ifthesecurityisnotimportant.
2.Ifnumberofuserliesbetween10to20.
3.Ifallusersaresituatedinthesamearea.
4.Ifthepossibilityoffutureexpansionisless.
AdvantagesofPeer-to-Peer(P2P)Architecture/Model:-
1.Useoflessexpensivehardware.i.e.Noextrainvestmentinserverhardwareor
softwareisrequired.
2.NoneedofNOSi.e.peertopeernetworkdonotrequireanetworkoperating
system.Itcanbebuiltbyusingjustlikewindows2000orwindowsXP.
3.Usercancontrolresourcesharing.
4.Nodependenceonothercomputersfortheiroperations.
55
S.P. Chauhan

56. Basic Concepts
ComputerNetworkArchitecture/Model:-
DisadvantagesofPeer-to-Peer(P2P)Architecture/Model:-
1.Notverysecure,aspeertopeernetworkrunsonmostcommondesktopoperating
systemslikewindowswhicharenotverysecureOS.Networksizeisverysmall,
eachuserisadministratingtheirownmachine,meanadministrationisdistributed
andonlyfewusersaregoodadministrators.
2.Hardtobackup:Inpeertopeernetworkthereisnocentralizedserver.Therefore,
dataisscatteredovermanyworkstations.Soitisdifficulttobackupalldata.
3.Lackofcentralmanagementwhichmakeslargepeernetworkshardtomanage.
4.Usersaresupposedtomanagetheirowncomputers.
5.Additionalloadoncomputersbecauseofresourcesharingandabsenceofserver.
56
S.P. Chauhan

57. Basic Concepts
ComputerNetworkArchitecture/Model:-
DifferenceBetweenPeer-to-Peer(P2P)&Client/ServerArchitecture/Model:-
57
S.P. Chauhan
S.No. Peer-to-Peer Client/server
1.
This model is ideal for networks
with 10 to15 computers.
No limit to the number of computers that
can be supported by the network.
2.They are easy to setup They are more difficult to setup
3.They are less expensive They aremore expensive
4.
These can be implemented on a
wide range of operating systems
A variety of operating systemscan be
supported on the client computers, but the
server needs to run an operating system
that supports networking.
5.
Very low levelsof security
supported or none at all
High levelsof security are supported, all of
which are controlled from the server.
6.
This model does not require a
server
Requires a server running server
operatingsystem.

58. Basic Concepts
LineConfiguration/Typesofconnection:-
Itreferstheway,howtwoormorecommunicationdevicesattachtoaCommunication
link.Thecommunicationlinkcanbewiredorwirelesslink.Alinkisaphysicalpath
usingwhichdatacanbetransferredbetweentwoormoredevices.Lineconfiguration
isalsoreferredtoasconnection/circuit.
Thecircuitisthepathoverwhichtwo-waycommunicationtakesplaceacircuitmay
exitsonmanydifferenttypesofmedia,suchaswire,fiber-opticorsatellite.Theword
lineisoftenusedinterchangeablywithcircuitalthoughlinegivesastronger
implicationofaphysicalwireconnection.
Forcommunicationtooccur,twodevicesmustbeconnectedinsomewaytothesame
linkatthesametime.“Lineconfigurationdefinestheattachmentofcommunication
devicestoalink”.TherearetwopossiblelineConfiguration:Point-toPoint&Multi
Point.
S.P. Chauhan
58

59. Basic Concepts
LineConfiguration/Typesofconnection:-
1.Point–to-Point:-
Itprovidededicatedlinkbetweentwocommunicatingdevices.Thetotalcapacityof
thelinkisusedforcommunicationbetweenthesetwodevices.
Itisalsocalledpointtopointcircuitortwopointcircuits.Itconnectsonlytwonodes.
Inpointtopointlink,twodevicesmonopolizeacommunicationmedium.Because
mediumisnotsharedandnomechanismisneededtoidentifythenodeandhence
pointtopointnetworkhasnoneedforaddressing.
Eg.Twocomputerscommunicatingviamodemsoraworkstationcommunicatinga
parallelcabletoaprinter.
Eg:Ifthelinkisa100MBPSlink,itmeans
100millionsbitscanbetransmittedper
secondandthese100millionbitscanbe
usedonlybythesetwonodes.Noother
devicecanclaimthisbecausethisisthelink
thatisexclusivelyb/wthesetwodevices
S.P. Chauhan
59

60. Basic Concepts
LineConfiguration/Typesofconnection:-
Itisconnectedthroughcableorwirebutsatelliteormicrowavelinkisalsopossible.In
mostpointtopointactuallengthofwireorcableisusedtoconnecttwodevices
ThePointtoPointProtocol(PPP)isusedtocreatedirectcommunicationbetweentwo
nodesinthenetwork.
Eg.CommunicationbetweenTelevisionandremotecontrolforchangingthechannels
throughinfraredrayorAcomputerconnectedbyatelephoneline.Similarityincaseof
voicecommunicationusingtelephones,thereisonecallingpartyandoneiscalled
partyandcommunicationispoint-to-point.
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S.P. Chauhan
1.Point–to-Point:-
Itisverysimpletosetup,understandand
maintain.
Itgivebetterperformancebecausetotalcapacityof
thelinkisusedforcommunicationbetweentwo
devices.Henceitisfasterthanasharedbroadcast
link.

61. Basic Concepts
LineConfiguration/Typesofconnection:-
2.MultiPoint:-ItisalsocalledMultidropconfigurationorbroadcastconnection.Inthis
lineconfigurationmultiplecommunicatingdevicesshareasinglelinki.e.thereisno
dedicatedlinkbetweencommunicatingdevicesi.e.twoormoredevicessharea
singlelinkasshowninfig.Soifthereareseveralnodesconnectedtothesamecircuit
iscalledmultipointormultidrop.
Themethodusedtoidentifythesendersandreceiversiscalledaddressing
Withsharedcapacity,therecanbetwopossibilitiesi.e.multipointcanbeSpatialor
Temporal.
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S.P. Chauhan
Asmorethantwodevicessharethelink,So
thechannelcapacityissharedbymorethan
onedevicessimultaneously.
Asmultipointshareacommonchannel,so
eachdeviceneedsawaytoidentifyitselfand
thedevicetowhichitwantstosenddata.

62. Basic Concepts
LineConfiguration/Typesofconnection:-
2.MultiPoint:-
Spatialmultipointconnection:-Ifseveraldevicescansharethelinksimultaneously,
itscalledSpatiallysharedlineconfiguration.Ifalldevicessharethesamelinkthen
theproblemofcollisionmayhappen.Iftwodevicessendthedataatthesametime
thencollisionmayhappen.Collisionmeanstwodatacollidewitheachotherandit
becomesunusable.
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S.P. Chauhan
TemporalMultipointConnection:-Inthis
devicessharelinkturnbyturni.e.allthe
deviceswillbehavingtheirownturntosend
thedata.Itisalsocalledtimeshared
connection.Inthiscollisionwillnothappen.

63. Basic Concepts
LineConfiguration/Typesofconnection:-
DifferencebetweenPoint-to-Point&Multipointconnection
63
S.P. Chauhan
S.NO Point to point communication Multipoint Communication
1
Pointtopointcommunicationmeansthe
channelissharedonlybetweentwodevices.
MultipointCommunicationmeansthechannelis
sharedamongmultipledevicesornodes.
2
Inthiscommunication,thereisdedicatedlink
betweentwonodes.
Inthiscommunication,linkisprovidedatall
timesforsharingtheconnectionamongnodes.
3
Inthiscommunication,theentirecapacityis
reservedbetweentheconnectedtwodevices
withthepossibilityofwasteofnetwork
bandwidth/resources.
Inthiscommunication,theentirecapacityisn’t
reservedbyanytwonodesandthenetwork
bandwidthismaximumutilized.
4
Inthiscommunication,thereisonetransmitter
andonereceiver.
Inthiscommunication,thereisonetransmitter
andmanyreceivers.
5
Inpoint-to-pointconnections,thesmallest
distanceismostimportanttoreachthe
receiver.
InMulti-pointconnections,thesmallestdistance
isnotimportanttoreachthereceiver.
6
Point-to-pointcommunication provides
securityandprivacybecausecommunication
channelisnotshared.
Multi-pointcommunicationdoesnotprovide
securityandprivacybecausecommunication
channelisshared.

64. Basic Concepts
Types of Transmission Technology :-
1.Broadcasting:-Thetermbroadcastingmeanssendingthemessagetoeverystation
onanetwork.Sobroadcastsystemsendsthesamesignaltoeveryonewhoreceives
it.Generallyitisonewayformsinglesourcetotheindividual
Ifaddressfieldofpacketismatchedwiththeaddressofreceivermachine,itis
processed,otherwisethepacketisignored.Thisaddressiscalledbroadcastaddress.
Asshowninthefig,thepacketfromnodeAisreceivedbyeveryothernodeofthe
network.Thelocalradio&televisionaregoodexamplesofpureone-waybroadcast
system.
S.P. Chauhan
64
Inbroadcastingsinglecommunication
channelissharedorusedbyallmachinesof
thatnetwork.Whenashortmessagescalled
packetissendbyanymachineisreceivedby
allothermachinesonthatnetwork.This
packetcontainsanAddressfieldwhichstore
theaddressofintendedreceiveroncemachine
receiveapacket,itcheckstheaddressfield.

65. Basic Concepts
Types of Transmission Technology :-
1.Broadcasting:-Inbroadcastsystemthereisaspecialcodeinaddressfieldofpacket
whichisintendedforalldestinationwhenpacketwiththiscodeistransmitteditis
supposedtobereceivedandprocessedbyallmachineonthatnetwork.Thismodeof
operationiscalledbroadcasting.Inbroadcastingthereisnoreversecommunication
path.
3.Unicasting:-Ifthereisonlyonesenderandonereceiverinanypoint-to-pointnetwork
65
S.P. Chauhan
2.Multicasting:-Whentransmissionistoasubset
ofmachinesorgroupbyusingabitinthe
addressfieldtoindicatethatthemessageis
intendedforthegroup.Inmulticastingon
receivingapacket,machinechecktheaddress
field.Ifthepacketisaddressedtoitthenpacket
isprocessed,otherwisepacketisignored.As
showninfig,thepacketfromnodeAisreceived
bythegroupofnodesC,D&Honlyi.e.the
subsetofthenetwork.

66. Basic Concepts
Network Functions:-
Followingaresomeimportantfunctionsthatanetworkneedstoperform:
1.Switching:-Itistheabilityofanetworktoconnectdifferentchannelsattachedtoeach
nodetoeachother.Thisisessentialformovingthetrafficfromincomingchanneltothe
desiredoutgoingchannel.
2.Routing:-Itdefinedastheabilityofthenetworktoselectapath.Theroutingcanbeof
differenttypessuchas:fixedroutingoralternaterouting.Theroutingcanalsobe
classifiedasstaticroutingordynamicrouting.
3.FlowControl:-Itisthecontrolovertherateoftraffic.Itisnecessaryinordertoreduce
thenetworkcongestion.
4.SpeedandCodeConversion:-Thespeedofdifferentdevicesmaybedifferent.Alsothe
codeusedbydifferentdevicesmaybedifferentfromeachother.Inthedigitalnetworks,
wehavetoallowthecommunicationbetweenallsuchdevices.
5.Security:-Itisdefinedastheabilityofnetworktodisallowanyunauthorizedaccessto
thenetworkandthedatatravellingoverit.Wehavetotakemeasuressuchasusing
passwordsoruseofencryptionandphysicalsecurity.
6.Backup:-Itistheabilityofanetworktoreactthecomponentfailures.Backupalso
includessendingtoindicatefailuresortoroutethetrafficviasomeotherpathtoavoida
failedcomponent.
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S.P. Chauhan

67. Basic Concepts
Network Functions:-
7.FailureMonitoring:-Itistheabilityofanetworktokeeptrackoffaultyandworking
components.
8.TrafficMonitoring:-Itisdefinedastheabilityofthenetworktokeeptrackoftraffic
level.Itisusefulfornetworkdesign.
9.Accountability:-Itistheabilityofthenetworktokeepatrackofwhoisactually
usingthenetwork.Itisdifferentfromtrafficmonitoring.
10.Internetworking:-Whentwoormorenetworksareconnectedtheyarecalled
internetworkofinternet.Individualnetworksarejoinedintointernetworksby
internetworkingdeviceslikebridges,routers,gateways.
Theterminternet(Lowercasei)isagenerictermusedtomeananinterconnection
ofnetworksandInternet(UppercaseI)isthenameofaspecificworldwide
network.AcommonformofinternetisacollectionofLAN’sconnectedbyaWAN.
Theinternetworkingincludethefollowingfunctions:
a.Toprovideroutesfortraffic
b.Toallocateresourcessuchasbuffersandlinks.
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68. Basic Concepts
Network Functions:-
11.NetworkManagement:-Thenetworkmanagementisnotaonesinglefunction.Itis
insteadacombinationofmanyfunction.Itincludesthefollowingfunctions:
a.Tomaintaintheuserslist.
b.Themaintaintheaddressesofthedevices.
c.Tokeepaneyeonchangesinschedulesofnetworks.
d.Faultisolation.
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