Fundamentals of Data Communication and Computer Networks

Fundamentals of Data Communication and Computer Networks Presented By Mr. C. P. Divate

1. Chapter 1
Fundamentals of Data
Communication and Computer
Networks
Mr. C. P. Divate
Department of Computer Engineering

2. Contents
1.0Objectives
1.1Data & Information
1.2Data Communication
1.2.1Characteristics of Data Communication
1.2.2Components of Data Communication
1.3Data Representation
1.4Data Flow
1.4.1. Simplex
1.4.2. Half Duplex
1.4.3. Full Duplex
1.5Computer Network
1.5.1Categories of a network
1.6Protocol
1.6.1Elements of a Protocol
1.7Standards In Networking
1.7.1Concept of Standard
1.7.2Standard Organizations in field of Networking
1.8Review Questions

3. 1.1Data and Information

4. 1.2Data Communication
•Datacommunicationistheprocesstoexchangeofdata
betweentwodevicesviasomeformoftransmission
mediumsuchasawirecableorwirelessmedium.

5. 1.2Data Communication in Computer Network
•DatacommunicationIncaseofcomputernetworksis
theprocessofexchangeofdatabetweentwodevices
overatransmissionmediumorwirelessmedium.

6. 1.2Data Communication Systems
•DatacommunicationSystemsThisinvolvesa
communicationsystemwhichismadeupofhardware
andsoftware.
•HardWarePart:Itinvolvesthesenderandreceiver
devicesandtheintermediatedevicesthroughwhichthe
datapasses.
•Softwarepart(Protocol):Itinvolvescertainruleswhich
specifywhatistobecommunicated,howitistobe
communicatedandwhen.ItisalsocalledasaProtocol.

7. 1.2Data Communication Systems
•DatacommunicationSystemsThisinvolvesa
communicationsystemwhichismadeupofhardware
andsoftware.

8. 1.2Data Communication Systems
•Softwarepart(Protocol):Itinvolvescertainruleswhich
specifywhatistobecommunicated,howitistobe
communicatedandwhen.ItisalsocalledasaProtocol.

9. 1.3 Components of a data communication system
1. Message
•Messageisthedata/informationtobecommunicatedbythesenderto
thereceiver.
•Amessagecouldbeinanyform,itmaybeinformofatextfile,anaudio
file,avideofile,etc.
•ThemessagecanbeofanysizefromonebytetoMegabyte.
•MessagecanbeofeitherAnalogorDigitalsignalformatdependingon
transmissionmedia(wired/wireless).

10. Figure 1.1 Components of a data communication system
2.Sender
•Thesenderisanydevicethatiscapableofsendingthedata(message).
•Thesenderdevicecouldbeinformofacomputer,mobile,telephone,
laptop,videocamera,oraworkstation,etc.
•Thesenderdevicemustkeephighmemorybufferforthesendinglargedata
/informationtomedium.
•Sendershouldtransmititsdatawithspeedasthatoftransmissionmedia
bandwidth(speed).
•Senderdevicemustbeloadedwithnetworkoperatingsystemthatcontains
allprotocolsoftransmission.

11. Figure 1.1 Components of a data communication system
3.Receiver
•Itisadevicethatreceivesmessage.
•Sameassender,receivercanalsobeinformofacomputer,telephone
mobile,workstation,etc.
•Thereceiverdevicemustkeephighmemorybufferforthelargelargedata/
informationfrommedium.
•Receivershouldreceivesitsdatawithspeedasthatoftransmissionmedia
bandwidth(speed).
•Receiverdevicemustbeloadedwithnetworkoperatingsystemthat
containsallprotocolsoftransmission.

12. Figure 1.1 Components of a data communication system
4. Transmission Medium
•Itisthepathbywhichthemessagetravelsfromsendertoreceiver.
•Itcanbewiredorwirelessandmanysubtypesinboth.
•Examplesaretwistedpaircable,fiberopticcable,radiowaves,
microwaves,etc.
•Thedatatransmissionrateformediumisdependingoftransmission
medium.
•Datatransmissionratesvariousfrom10Mbpsto1000Gbps
•Thedatatransmissionmediumisconnectedtodifferentnetworking
devicesbetweensenderandreceiver.

13. Figure 1.1 Components of a data communication system
5. Protocols
•Itisanagreementofsetorrulesusedbythesenderandreceiverto
communicatedata.
•Aprotocolisasetofrulesthatgovernsdatacommunication.
•AProtocolisanecessityindatacommunicationswithoutwhichthe
communicatingentitiesareliketwopersonstryingtotalktoeachotherin
adifferentlanguagewithoutknowtheotherlanguage.
•Itprovidessecuritytodatamessagesontransmissionmedium.
•ExamplesOSIModel,TCP/IP,UDP/IP,FTP,DHCP,PPPetc.

14. Figure 1.1 Characteristics of Data Communication
Theeffectivenessofanydatacommunicationssystemdependsuponthe
followingfundamentalcharacteristics:
1.Delivery:Thedatashouldbedeliveredtothecorrectdestinationandcorrect
user.
2.Accuracy/Integrity:Thecommunicationsystemshoulddeliverthedata
accurately,withoutintroducinganyerrors.Thedatamaygetcorruptedduring
transmissionaffectingtheaccuracyofthedelivereddata.
3.Timeliness:AudioandVideodatahastobedeliveredinatimelymanner
withoutanydelay;suchadatadeliveryiscalledrealtimetransmissionofdata.
4.Jitter:Itisthevariationinthepacketarrivaltime.UnevenJittermayaffectthe
timelinessofdatabeingtransmitted.

15. Figure 1.1 Characteristics of Data Communication
Theeffectivenessofanydatacommunicationssystemdependsuponthe
followingfundamentalcharacteristics:
5.Errordetection&Correction:Thedatacommunicationsystemsshould
communicatewithautomaticdetecterrorsandcorrecterrorsinmessages
duringthetransmissions.e.g.Paritycheck,Checksum,CRC
6.Routing-Routingmeanstosenddatatoappropriatedestinations.Itisusedto
findshortestpathamongdeviseorserver.
7.Reliable:Itismeasuredbyfrequencyoffailure,thetimeittakesalinkto
recoverfromafailure,andthenetwork’srobustness.
8.FlowControl:Atthetimeoftransmissionofdata,sourcecomputeris
generatingdatafasterthanreceiverdevicecapabletoreceiveit.Tohandle
suchproblem,thereissomekindofflowcontrolmechanismused.

16. Figure 1.1 Characteristics of Data Communication
Theeffectivenessofanydatacommunicationssystemdependsuponthe
followingfundamentalcharacteristics:
9.Security:Securityissuesincludeprotectingdatafromunauthorizedaccessand
virus.Networkmustbesecured.Thedatathatissentshouldreachits
destinationsafelywithoutanythird-partyreadingoralteringordestroyingthe
datainthemidway.
10.Performance:Itmeansachievinghigherthroughput(numberofUsersin
network)andsmallerdelaytimes(datatransmissiondelaybetweensenderand
receiver)

17. 1.17
Figure 1.2 Data flow / Transmission modes in communication systems
(simplex, half-duplex, and full-duplex)
•The way in which data is transmitted from one device to another device is
known astransmission mode.
•The transmission mode is also known as the communication mode.
•Each communication channel has a direction associated with it, and
transmission media provide the direction. Therefore, the transmission mode
is also known as a directional mode.
•The transmission mode is defined in the physical layer.

18. 1.18
Figure 1.2 Data flow / Transmission modes in communication systems
(simplex, half-duplex, and full-duplex)
The Transmission mode is divided into three categories
•Simplex mode
•Half-duplex mode
•Full-duplex mode

19. 1.19
Figure 1.2 Data flow / Transmission modes in communication systems
(simplex, half-duplex, and full-duplex)

20. 1.20
Figure 1.2 Data flow / Transmission modes in communication systems -simplex
•InSimplexmode,thecommunicationisunidirectional,i.e.,the
dataflowinonedirection.
•Adevicecanonlysendthedatabutcannotreceiveitoritcan
receivethedatabutcannotsendthedata.
•Thistransmissionmodeisnotverypopularasmainly
communicationsrequirethetwo-wayexchangeofdata.
•Themainadvantageofthesimplexmodeisthatthefull
capacityofthecommunicationchannelcanbeutilizedduring
transmission.

21. 1.21
Figure 1.2 Data flow / Transmission modes in communication systems -simplex
ExamplesofSimplexTransmissionmodes:
•Thesimplexmodeisusedinthebusinessfieldasinsalesthat
donotrequireanycorrespondingreply.
•Theradiostationisasimplexchannelasittransmitsthesignal
tothelistenersbutneverallowsthemtotransmitback.
•KeyboardandMonitoraretheexamplesofthesimplexmodeas
akeyboardcanonlyacceptthedatafromtheuserandmonitor
canonlybeusedtodisplaythedataonthescreen.

22. 1.22
Figure 1.2 Data flow / Transmission modes in communication systems -simplex
AdvantageofSimplexmode:
•Insimplexmode,thestationcanutilizetheentirebandwidthof
thecommunication channel,sothatmoredatacanbe
transmittedatatime.
DisadvantageofSimplexmode:
•Communication isunidirectional,soithasnointer-
communicationbetweendevices.

23. 1.23
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode
•InaHalf-duplexchannel,directioncanbereversed,i.e.,thestationcan
transmitandreceivethedataaswell.
•Messagesflowinboththedirections,butnotatthesametime.
•Theentirebandwidthofthecommunicationchannelisutilizedinone
directionatatime.
•Inhalf-duplexmode,itispossibletoperformtheerrordetection,andif
anyerroroccurs,thenthereceiverrequeststhesendertoretransmitthe
data.

24. 1.24
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode

25. 1.25
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode (Stop –and –Wait Protocol)

26. 1.26
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode (Stop –and –Wait Protocol with sliding window)

27. 1.27
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode
ExamplesofHalfDuplexTransmissionmodes:
•AWalkie-talkie:InWalkie-talkie,onepartyspeaks,andanotherparty
listens.Afterapause,theotherspeaksandfirstpartylistens.Speaking
simultaneouslywillcreatethedistortedsoundwhichcannotbe
understood.
•WhatsAppMessenger,Facebookmessenger,MobileMessengeretc.
•ATMMachine,BusTicketmachines

28. 1.28
Figure 1.2 Data flow / Transmission modes in communication systems -Half-
Duplex mode
AdvantageofHalf-duplexmode:
•Inhalf-duplexmode,boththedevicescansendandreceive
thedataandalsocanutilizetheentirebandwidthofthe
communicationchannelduringthetransmissionofdata.
DisadvantageofHalf-Duplexmode:
•Inhalf-duplexmode,whenonedeviceissendingthedata,
thenanotherhastowait,thiscausesthedelayinsending
thedataattherighttime.

29. 1.29
Figure 1.2 Data flow / Transmission modes in communication systems -Full-
Duplex mode
•InFullduplexmode,thecommunicationisbi-directional,i.e.,thedata
flowinboththedirections.
•Boththestationscansendandreceivethemessagesimultaneously.
•Full-duplexmodehastwosimplexchannels.Onechannelhastraffic
movinginonedirection,andanotherchannelhastrafficflowinginthe
oppositedirection.
•TheFull-duplexmodeisthefastestmodeofcommunicationbetween
devices.

30. 1.30
Figure 1.2 Data flow / Transmission modes in communication systems -Full-
Duplex mode(sliding window protocol)

31. 1.31
Figure 1.2 Data flow / Transmission modes in communication systems -Full-
Duplex mode
ExamplesofFullDuplexTransmissionmodes:
•Telephone/Mobilecommunication:Themostcommonexampleofthe
full-duplexmodeisatelephonenetwork.Whentwopeopleare
communicatingwitheachotherbyatelephoneline,bothcantalkand
listenatthesametime.

32. 1.32
Figure 1.2 Data flow / Transmission modes in communication systems -Full-
Duplex mode
AdvantageofFull-duplexmode:
•Boththestationscansendandreceivethedataatthe
sametime.
DisadvantageofFull-duplexmode:
•Ifthereisnodedicatedpathexistsbetweenthedevices,
thenthecapacityofthecommunicationchannelisdivided
intotwoparts.

33. PROTOCOL
•AProtocolisoneofthecomponentsofadatacommunicationssystem.
Withoutprotocolcommunicationcannotoccur.
•Thesendingdevicecannotjustsendthedataandexpectthereceivingdevice
toreceiveandfurtherinterpretitcorrectly.
•Whenthesendersendsamessageitmayconsistoftext,number,images,etc.
whichareconvertedintobitsandgroupedintoblockstobetransmittedand
oftencertainadditionalinformationcalledcontrolinformationisalsoadded
tohelpthereceiverinterpretthedata.

34. PROTOCOL
•AProtocolisoneofthecomponentsofadatacommunicationssystem.
Withoutprotocolcommunicationcannotoccur.
•Thesendingdevicecannotjustsendthedataandexpectthereceivingdevice
toreceiveandfurtherinterpretitcorrectly.
•Whenthesendersendsamessageitmayconsistoftext,number,images,etc.
whichareconvertedintobitsandgroupedintoblocks(packets/frames)tobe
transmitted

35. 1.35
PROTOCOL
•Certainadditionalinformationcalledcontrolinformationisalsoaddedto
helpthereceiverinterpretthedata.
•Forsuccessfulcommunicationtooccur,thesenderandreceivermustagree
uponcertainrulescalledprotocol.
•AProtocolisdefinedasasetofrulesthatgovernsdatacommunications.
•Aprotocoldefineswhatistobecommunicated,howitistobe
communicatedandwhenitistobecommunicated.

36. 1.36
PROTOCOL
•Certainadditionalinformationcalledcontrolinformationisalsoaddedto
helpthereceiverinterpretthedata.
•AProtocolisdefinedasasetofrulesthatgovernsdatacommunications.
•Aprotocoldefineswhatistobecommunicated,howitistobe
communicatedandwhenitistobecommunicated.

37. 1.37
TCP/IP PROTOCOL
•Certainadditionalinformationcalledcontrolinformationisalsoaddedto
helpthereceiverinterpretthedata.
•AProtocolisdefinedasasetofrulesthatgovernsdatacommunications.
•Aprotocoldefineswhatistobecommunicated,howitistobe
communicatedandwhenitistobecommunicated.

38. 1.38
TCP/IP PROTOCOL
•Certainadditionalinformationcalledcontrolinformationisalsoaddedto
helpthereceiverinterpretthedata.
•AProtocolisdefinedasasetofrulesthatgovernsdatacommunications.

39. Elements of a Protocol
Therearethreekeyelementsofaprotocol:
A.Syntax:
•Itmakesthestructureorformatofthedata.
•Itarrangesthedataframesinaparticularorder.
B.Semantics:
•Ittellsthemeaningofeachsectionofbitsandindicatesthe
interpretationofeachsection.
•Italsotellswhataction/decisionistobetakenbasedonthe
interpretation.
•ErrorHandling.
C.Timing:
•Ittellsthesenderaboutthereadinessofthereceivertoreceivethe
data.
•Ittellsthesenderatwhatratethedatashouldbesenttothe
receivertoavoidoverwhelmingthereceiver.

40. STANDARDS IN NETWORKING
•Standardsarenecessaryinnetworkingtoensureinterconnectivityand
interoperabilitybetweenvariousnetworkinghardwareandsoftware
components.
•Withoutstandardswewouldhaveproprietaryproductscreating
isolatedislandsofuserswhichcannotinterconnect.

41. STANDARDS IN NETWORKING
ConceptofStandard
•Standardsprovideguidelinestoproductmanufacturersandvendorsto
ensurenationalandinternationalinterconnectivity.
•Datacommunicationsstandardsareclassifiedintotwocategories:
1.DefactoStandard-designedbyfactsincommunication
•Thesearethestandardsthathavebeentraditionallyused
andmeanbyfactorbyconvention
•Thesestandardsarenotapprovedbyanyorganizedbody
butareadoptedbywidespreaduse.
2.Dejurestandarddesignedbylawincommunication
•Itmeansbylaworbyregulation.
•Thesestandardsarelegislatedandapprovedbyanbody
thatisofficiallyrecognized.

42. STANDARDS IN NETWORKING
De Facto De Jure
Factual Recognition is known as De FactoLegal Recognition is known as De Jure
De Facto is temporary. It is not permanent
like De Jure.
De Jure which is a legal recognition is a
permanent recognition
It is a temporary and provisional recognition
which can be withdrawn.
it cannot be withdrawn.
The recognition by De Facto is based on a
factual situation and is not a process of law.
De Jure is a recognition given after following due
procedure of law.
State Succession rules do not apply in de
facto
Under De Jure, rules of state succession are
applied.
De Facto Government cannot recover a state
asset or public debt
Only a de jure government can recover state
assets or public debt.
Membership to theUnited Nationsis not
possible even if there is a de facto
recognition by the majority of states.
A state can get United Nations membership if the
majority of nations bestows de jure recognition.
The State which receives De facto
recognition will have 2 rival governments
The State which receives De Jure recognition
has only 1 Government.

43. Standard Organizations in field of Networking
Standardsarecreatedbystandardscreationcommittees,forums,and
governmentregulatoryagencies.
•Examples of Standard Creation Committees :
i.International Organization for Standardization (ISO)
ii.International Telecommunications Union –Telecommunications
Standard (ITU-T)
iii.American National Standards Institute (ANSI)
iv.Institute of Electrical& Electronics Engineers (IEEE)
v.Electronic Industries Associates (EIA)
•Examples of Forums
i.ATM Forum -Asynchronous Transfer Mode
ii.MPLS Forum -Multiprotocol Label Switching
iii.Frame Relay Forum
•Examples of Regulatory Agencies:
i. Federal Communications Committee (FCC)

44. DATA & SIGNALS
Totransmit,dataovermedium,itmustbetransformedtoelectromagnetic
signals.•Data can be Analog or Digital:

45. ANOLOG DATA & SIGNALS
•Analogdatareferstoinformationthatiscontinuous;ex.soundsmadeby
ahumanvoice
•AnalogSignal:Theyhaveinfinitevaluesinarange.
•SignalswhichrepeatitselfafterafixedtimeperiodarecalledPeriodic
Signals.
•Indatacommunications,wecommonlyuseperiodicanalogsignalsand
non-periodicdigitalsignals.

46. DIGITAL DATA & SIGNALS
•Digitaldatareferstoinformationthathasdiscretestates.Digitaldatatake
ondiscretevalues.
•Forexample,dataarestoredincomputermemoryintheformofOsand
1s.
•DigitalSignal:Theyhavelimitednumberofdefinedvalues
•SignalswhichdonotrepeatitselfafterafixedtimeperiodarecalledNon-
PeriodicSignals.
•Indatacommunications,wecommonlyuseperiodicanalogsignalsand
non-periodicdigitalsignals.

47. DATA & SIGNALS
Totransmit,dataovermedium,itmustbetransformedtoelectromagnetic
signals.•Data can be Analog or Digital:
Analog signals Digital signals
There is a continuous
representation of signals in analog
signals.
There is a discontinuous
representation of signals in digital
signals.
Analog signals are difficult to get
analyzed at first.
Digital signals are easy to analyze.
Analog signals are more accurate
than digital signals.
Digital signals are less accurate.
Analog signals take time to be
stored. It has infinite memory.
Digital signals can be easily stored.
To record an analog signal, the
technique used, preserves the
original signals.
In recording digital signal, the sample
signals are taken and preserved.

48. DATA & SIGNALS
Totransmit,dataovermedium,itmustbetransformedtoelectromagnetic
signals.•Data can be Analog or Digital:
Analog signals. Digital signals
Analog signals produce too much
noise.
Digital signals do not produce noise.
Applications of analog signals are
Human voice, Thermometer, Analog
phones etc.
Examples of digital signals are
Computers, Digital Phones, Digital
pens, etc.
Represented by sine waves Represented by square waves
Records sound waves as they areConverts into a binary waveform.
Only be used in analog devices.
Suited for digital electronics like
computers, mobiles and more.

49. DATA & SIGNALS
•BIT LENGTH or Bit Interval (T
b)
•It is the time required to send one bit.
•It is measured in seconds.
•BIT RATE / bits per second
•It is the number of bits transmitted in one second. It is expressed as
bits per second (bps).
•Relation between bit rate and bit interval can be as follows Bit rate =
1 / Bit interval

50. DATA & SIGNALS
•Baud Rate
•ItistherateofSignalSpeed,i.etherateatwhichthesignal
changes.
•Adigitalsignalwithtwolevels‗0‘&‗1‘willhavethesamebaudrate
andbitrate&bitrate.
•Thediagrambelowshowsthreesignalofperiod(T)1second
a) Signal with a bit rate of 8 bits/ sec and baud rate of 8 baud/sec
b) Signal with a bit rate of 16 bits/ sec and baud rate of 8 baud/sec
c) Signal with a bit rate of 16 bits/ sec and baud rate of 4 baud/sec

51. DATA & SIGNALS

52. Conversion of Analog signals to Digital signals
•Mostoftheimage/audiosensorsareintheanalogsignal,anddigital
processingcannotbeappliedonit,asitrequiresinfinitememoryto
storebecausesignalshaveaninfinitevaluethatiswhywecannot
storeit.
•Adigitalsignalissuperiortoananalogsignalbecauseitismore
robusttonoiseandcaneasilyberecovered,correctedandamplified.
•Forthisreason,thetendencytodayistochangeananalogsignalto
digitaldata.Inthissectionwedescribetwotechniques,pulsecode
modulationanddeltamodulation.
•Tocreateadigitalimagewecanconvertdataintodigitalform.
•Fortheconversiontherearethreesteps:
1.Sampling
2.Quantization
3.Encoding

53. 4.53
Figure 4.21 Components of PCM encoder
Conversion of Analog signals to Digital signals

54. Conversion of Analog signals to Digital signals
i) Sampling
•Inanalogsignals,therearecontinuouselectricalsignals
thatvarywithtime.Withthehelpofsubsystem,asampler
extractscontinuoussignalsforthesamplingofsignals.
•Sampling is done along the x-axis of signals that continuously differs
with time. It is divided into two category one is sampling and other is
down-sampling.
•In down-sampling, the range of values on the x-axis is always less.

55. i) Sampling
Analog signal is sampled every T
Ssecs.
T
sis referred to as the sampling interval.
f
s= 1/T
sis called the sampling rate or sampling
frequency.
There are 3 sampling methods:
Ideal -an impulse at each sampling instant
Natural -a pulse of short width with varying
amplitude.
Flattop -sample and hold, like natural but
with single amplitude value
The process is referred to as pulse amplitude
modulation PAM and the outcome is a signal with
analog (non integer) values
Conversion of Analog signals to Digital signals

56. 4.56
Figure 4.22 Three different sampling methods for PCM
Conversion of Analog signals to Digital signals

57. Conversion of Analog signals to Digital signals
Quantization
•Itisaprocessofimageprocessing,inwhichcontinuousand
time-varyingvaluesofanalogsignalsaredividedintonon-
overlappingdiscreteanduniquevaluesassignedtoeach
subrange.
•Samplingandquantizationareoppositetoeachother.
Samplingisdonealongthex-axisbutquantizationisdone
alongthey-axis.
•Intheimageprocessing,thesampledimageisconsideredasa
digitalvalue.Whenthereisatransitionofstatesbetween
time-varyingvaluesofimagefunctionanditsdigitalequivalent
signifiesquantization.

58. Conversion of Analog signals to Digital signals
Quantization

59. ii) Quantization
Samplingresultsinaseriesofpulsesof
varyingamplitudevaluesrangingbetween
twolimits:aminandamax.
Theamplitudevaluesareinfinitebetween
thetwolimits.
Weneedtomaptheinfiniteamplitude
valuesontoafinitesetofknownvalues.
Thisisachievedbydividingthedistance
betweenminandmaxintoLzones,eachof
height
=(max-min)/L
Conversion of Analog signals to Digital signals

60. Quantization Levels
Themidpointofeachzoneisassignedavalue
from0toL-1(resultinginLvalues).
Eachsamplefallinginazoneisthen
approximatedtothevalueofthemidpoint.
Quantization Zones
Assume we have a voltage signal with amplitutes
V
min=-20V and V
max=+20V.
We want to use L=8 quantization levels.
Zone width= (20 --20)/8 = 5
The 8 zones are: -20 to -15, -15 to -10, -10 to -5, -5
to 0, 0 to +5, +5 to +10, +10 to +15, +15 to +20
The midpoints are: -17.5, -12.5, -7.5, -2.5, 2.5, 7.5,
12.5, 17.5
Conversion of Analog signals to Digital signals

61. Assigning Codes to Zones
Eachzoneisthenassignedabinarycode.
Thenumberofbitsrequiredtoencodethezones,or
thenumberofbitspersampleasitiscommonly
referredto,isobtainedasfollows:
n
b=log
2L
Givenourexample,n
b=3
The8zone(orlevel)codesaretherefore:000,001,
010,011,100,101,110,and111
Assigningcodestozones:
000willrefertozone-20to-15
001tozone-15to-10,etc.
Conversion of Analog signals to Digital signals

62. Figure 4.26 Quantization and encoding of a sampled signal

63. PCM Decoder
Torecoverananalogsignalfromadigitizedsignal
wefollowthefollowingsteps:
Weuseaholdcircuitthatholdstheamplitude
valueofapulsetillthenextpulsearrives.
Wepassthissignalthroughalowpassfilterwith
acutofffrequencythatisequaltothehighest
frequencyinthepre-sampledsignal.
ThehigherthevalueofL,thelessdistortedasignal
isrecovered.
Conversion of Digital signals to Analog signals

64. Figure 4.27 Components of a PCM decoder

65. Figure 4.31 Data transmission methods

66. Figure 4.32 Parallel transmission

67. Figure 4.33 Serial transmission

68. In asynchronous transmission, we send
1 start bit (0) at the beginning and 1 or
more stop bits (1s) at the end of each
byte. There may be a gap between
each byte.
Note

69. Asynchronous here means
“asynchronous at the byte level,”
but the bits are still synchronized;
their durations are the same.
Note

70. Figure 4.34 Asynchronous transmission

71. In synchronous transmission, we send
bits one after another without start or
stop bits or gaps. It is the responsibility
of the receiver to group the bits. The bits
are usually sent as bytes and many
bytes are grouped in a frame. A frame is
identified with a start and an end byte.
Note

72. Figure 4.35 Synchronous transmission

73. Isochronous
In isochronous transmission we cannot
have uneven gaps between frames.
Transmission of bits is fixed with equal
gaps.

74. Fundamentals of Computer Networks
DefinitionofComputerNetworks
Acomputernetworkisagroupofcomputerslinked
toeachotherthatenablesthecomputerto
communicatewithanothercomputerandshare
theirresources,data,andapplications.

75. Fundamentals of Computer Networks
NeedofComputerNetworks
HighCommunicationspeed
Filesharing
BackupandRollbackisofdataiseasy
SoftwareandHardwaresharing
Security
Scalability
Reliability
Email
Internetaccess
eCommerce
Resourcesharing

76. Fundamentals of Computer Networks
ApplicationsofComputerNetworks
Email-e.g.gmail,rocketmail,rediffmailetc.
FileTransferProtocol(FTP)-playstore,youtubeetc.
TerminalEmulation(TELNET)-playstore
eCommerce-amazon,flipcart,bankingetc.
videoconferencingandchatting-zoom,googlemeet
whatsappetc.
Onlinegaming
Filesharing-Googledriveetc.
Sharingresources-anydesketc.

77. Fundamentals of Computer Networks
ComputerNetworkArchitecture
ComputerNetworkArchitectureisdefinedasthe
physicalandlogicaldesignofthesoftware,
hardware,protocols,andmediaofthetransmission
ofdata.
Simplywecansaythathowcomputersare
organizedandhowtasksareallocatedtothe
computer.
ThetwotypesComputerNetworkArchitecturesare:
Peer-To-Peernetwork
Client/Servernetwork

78. Fundamentals of Computer Networks
Peer-To-PeerNetworkArchitecture

79. Fundamentals of Computer Networks
Peer-To-PeerNetworkArchitecture
Peer-To-Peernetworkisanetworkinwhichallthecomputers
arelinkedtogetherwithequalprivilegeandresponsibilitiesfor
processingthedata.
Peer-To-Peernetworkisusefulforsmallenvironments,
usuallyupto10computers.
Peer-To-Peernetworkhasnodedicatedserver.
Specialpermissionsareassignedtoeachcomputerfor
sharingtheresources,butthiscanleadtoaproblemifthe
computerwiththeresourceisdown.
Peeristhecomputerthatworksasclientaswellasserver
withlimitedaccesstoitsresources.

80. Fundamentals of Computer Networks
AdvantagesOfPeer-To-PeerNetwork:
Itislesscostlyasitdoesnotcontainanydedicatedserver.
Ifonecomputerstopsworkingbut,othercomputerswillnot
stopworking.
Itiseasytosetupandmaintainaseachcomputermanages
itself.
DisadvantagesOfPeer-To-PeerNetwork:
InthecaseofPeer-To-Peernetwork,itdoesnotcontainthe
centralizedsystem.Therefore,itcannotbackupthedataas
thedataisdifferentindifferentlocations.
Ithasasecurityissueasthedeviceismanageditself.
Difficulttoavoiddatareplication.
Difficulttomaintainversioncontrolofdata.

81. Fundamentals of Computer Networks
Client/ServerNetworkArchitecture

82. Fundamentals of Computer Networks
Client/ServerNetworkArchitecture
Serveristhecomputerthatprovidesdifferentservicestoall
othercomputersinnetwork.
Clientisthecomputerthatacceptsservicesfromserver
machines.
Client/Servernetworkisanetworkmodeldesignedfortheend
userscalledclients,toaccesstheresourcessuchassongs,
video,etc.fromacentralcomputerknownasServer.
Thecentralcontrollerisknownasaserverwhileallother
computersinthenetworkarecalledclients.
Aserverperformsallthemajoroperationssuchassecurity
andnetworkmanagement.
Aserverisresponsibleformanagingalltheresourcessuchas
files,directories,printer,etc.
Alltheclientscommunicatewitheachotherthroughaserver.
Forexample,ifclient1wantstosendsomedatatoclient2,
thenitfirstsendstherequesttotheserverforthepermission.
Theserversendstheresponsetotheclient1toinitiateits
communicationwiththeclient2.

83. Fundamentals of Computer Networks
AdvantagesOfClient/ServerNetwork:
AClient/Servernetworkcontainsthecentralizedsystem.
Thereforewecanbackupthedataeasily.
AClient/Servernetworkhasadedicatedserverthatimproves
theoverallperformanceofthewholesystem.
SecurityisbetterinClient/Servernetworkasasingleserver
administersthesharedresources.
Italsoincreasesthespeedofthesharingresources.
Avoidduplicationofdataonallcomputers
Versioncontrolasnoduplicationofdataonothercomputers
onlysingleandfinalcopyofdataismaintainedcentrally.

84. Fundamentals of Computer Networks
DisadvantagesOfClient/ServerNetwork:
Client/Servernetworkisexpensiveasitrequirestheserver
withlargememory.
AserverhasaNetworkOperatingSystem(NOS)toprovidethe
resourcestotheclients,butthecostofNOSisveryhigh.
Itrequiresadedicatednetworkadministratortomanageall
theresources.
Requiresbackupofdataatserverside.

85. Classification of Computer Networks
Acomputernetworkcanbecategorizedbytheir
size.Acomputernetworkismainlyoffourtypes:
i.LAN(LocalAreaNetwork)
ii.PAN(PersonalAreaNetwork)
iii.MAN(MetropolitanAreaNetwork)
iv.WAN(WideAreaNetwork)

86. Classification of Computer Networks
PAN(PersonalAreaNetwork):
PersonalAreaNetworkisanetworkarrangedwithinan
individualperson,typicallywithinarangeof10meters.
PersonalAreaNetworkisusedforconnectingthecomputer
devicesofpersonaluseisknownasPersonalAreaNetwork.
ThomasZimmerman wasthefirstresearchscientisttobring
theideaofthePersonalAreaNetwork.
PersonalAreaNetworkcoversanareaof30feet.
Personalcomputerdevicesthatareusedtodevelopthe
personalareanetworkarethelaptop,mobilephones,media
playerandplaystations.
ConnectioncanbemadeavailableforBluetoothwithinfrared
signals.

87. Classification of Computer Networks
PAN(PersonalAreaNetwork):

88. Classification of Computer Networks
TherearetwotypesofPersonalAreaNetwork:
WiredPersonalAreaNetwork
WirelessPersonalAreaNetwork
WirelessPersonalAreaNetwork:WirelessPersonalArea
Networkisdevelopedbysimplyusingwirelesstechnologies
suchasWiFi,Bluetooth.Itisalowrangenetwork.
WiredPersonalAreaNetwork:WiredPersonalAreaNetwork
iscreatedbyusingtheUSB.
PAN(PersonalAreaNetwork):

89. Classification of Computer Networks
AdvantagesOfPANNetwork:
WireRequirement
DeviceConnectivity
Portability
Reliable
DisadvantagesOfPeer-To-PeerNetwork:
AreaCoverage
SignalInterference
DataTransferRate
Cost
PAN(PersonalAreaNetwork):

90. Classification of Computer Networks
LAN(LocalAreaNetwork):
LocalAreaNetworkisagroupofcomputersconnectedtoeach
otherinasmallareasuchasbuilding,office.
LANisusedforconnectingtwoormorepersonalcomputers
throughacommunicationmediumsuchastwistedpair,
coaxialcable,etc.
Itislesscostlyasitisbuiltwithinexpensivehardwaresuch
ashubs,networkadapters,andethernetcables.
ThedataistransferredatanextremelyfasterrateinLocal
AreaNetwork.
LocalAreaNetworkprovideshighersecurity.

91. Classification of Computer Networks
LAN(LocalAreaNetwork):

92. Classification of Computer Networks
AdvantagesOfLANNetwork:
ResourceSharing
SoftwareApplicationsSharing
EasyandCheapCommunication
CentralizedData
DataSecurity
InternetSharing
LAN(PersonalAreaNetwork):

93. Classification of Computer Networks
DisadvantagesOfLANNetwork:
HighSetupCost
PrivacyViolations
DataSecurityThreat
LANMaintenanceJob
CoversLimitedArea
ConnectsLimitedusers
LAN(PersonalAreaNetwork):

94. Classification of Computer Networks
MAN(MetropolitanAreaNetwork):
Ametropolitanareanetworkisanetworkthatcoversalarger
geographicareabyinterconnectingadifferentLANtoforma
largernetwork.
GovernmentagenciesuseMANtoconnecttothecitizensand
privateindustries.
InMAN,variousLANsareconnectedtoeachotherthrougha
telephoneexchangeline.
ThemostwidelyusedprotocolsinMANareRS-232,Frame
Relay,ATM,ISDN,OC-3,ADSL,etc.
IthasahigherrangethanLocalAreaNetwork(LAN).

95. Classification of Computer Networks
MAN(MetropolitanAreaNetwork):

96. Classification of Computer Networks
MANisusedincommunicationbetweenthebanksina
city.
ItcanbeusedinanAirlineReservation.
Itcanbeusedinacollegewithinacity.
Itcanalsobeusedforcommunicationinthemilitary.
Uses/ApplicationsOfMetropolitanAreaNetwork:
Examplesofmetropolitanareanetwork(MAN):
•Digital cable television
•Used in government agencies
•University campuses
•Cable broadband
•Used to connect several branches of the local school
•In hospital (for communication between doctors, research offices, labs)
•A network of fire stations
•In airports
•Networking between community colleges within the country
•Used in public libraries

97. Classification of Computer Networks
AdvantagesOfMetropolitanAreaNetwork:
Lessexpensive:ItislessexpensivetoattachMANwith
WAN.
Sendinglocalemails
HighspeedthanWAN
Sharingoftheinternet
ConversionfromLANtoMANiseasy
HighSecurity
MAN(MetropolitanAreaNetwork):

98. Classification of Computer Networks
disadvantagesOfMetropolitanAreaNetwork:
Difficulttomanage.
Internetspeeddifference
Hackersattack
Technicalpeoplerequiredtosetup
ConversionfromLANtoMANiseasy
Morewiresrequired
MAN(MetropolitanAreaNetwork):

99. Classification of Computer Networks
DisadvantagesOfMetropolitanAreaNetwork:
Securityissue:AWANnetworkhasmoresecurityissuesas
comparedtoLANandMANnetworkasallthetechnologiesare
combinedtogetherthatcreatesthesecurityproblem.
NeedsFirewall&antivirussoftware:Thedataistransferred
ontheinternetwhichcanbechangedorhackedbythe
hackers,sothefirewallneedstobeused.Somepeoplecan
injectthevirusinoursystemsoantivirusisneededtoprotect
fromsuchavirus.
HighSetupcost:AninstallationcostoftheWANnetworkis
highasitinvolvesthepurchasingofrouters,switches.
Troubleshootingproblems:Itcoversalargeareasofixingthe
problemisdifficult.
MAN(MetropolitanAreaNetwork):

100. Classification of Computer Networks
WAN(WideAreaNetwork):
AWideAreaNetworkisanetworkthatextendsoveralarge
geographicalareasuchasstatesorcountries.
AWideAreaNetworkisquitebiggernetworkthantheLANandMAN.
AWideAreaNetworkisnotlimitedtoasinglelocation,butitspans
overalargegeographicalareathroughatelephoneline,fibreoptic
cableorsatellitelinks.
wideareanetworksareaformoftelecommunicationnetworksthat
canconnectdevicesfrommultiplelocationsandacrosstheglobe.
WANsarethelargestandmostexpansiveformsofcomputer
networksavailabletodate.TheinternetisoneofthebiggestWANin
theworld.
AWideAreaNetworkiswidelyusedinthefieldofBusiness,
government,andeducation.
Thesenetworksareoftenestablishedbyserviceprovidersthatthen
leasetheirWANtobusinesses,schools,governmentsorthepublic.

101. Classification of Computer Networks
WAN(WideAreaNetwork):

102. Classification of Computer Networks
Internet
USdefensedepartment
Stockexchangesnetwork
Railwayreservationsystem
BigBanks'cashdispensers'network
Satellitesystems
Uses/ApplicationsOfWideAreaNetwork:
ExamplesOfWideAreaNetwork:
•Mobile Broadband
•Private network
•Government network
•Last mile: A telecom company
•Internet Banking

103. Classification of Computer Networks
AdvantagesOfWideAreaNetwork:
Geographicalarea:AWideAreaNetworkprovidesalarge
geographicalarea.Supposeifthebranchofourofficeisina
differentcitythenwecanconnectwiththemthroughWAN.
Theinternetprovidesaleasedlinethroughwhichwecan
connectwithanotherbranch.
Centralizeddata:IncaseofWANnetwork,datais
centralized.Therefore,wedonotneedtobuytheemails,files
orbackupservers.
Getupdatedfiles:Softwarecompaniesworkonthelive
server.Therefore,theprogrammersgettheupdatedfiles
withinseconds.
WAN(WideAreaNetwork):

104. Classification of Computer Networks
AdvantagesOfWideAreaNetwork:
Exchangemessages:InaWANnetwork,messagesare
transmittedfast.ThewebapplicationlikeFacebook,
Whatsapp,Skypeallowsyoutocommunicatewithfriends.
Sharingofsoftwareandresources:InWANnetwork,wecan
sharethesoftwareandotherresourceslikeaharddrive,
RAM.
Globalbusiness:Wecandothebusinessovertheinternet
globally.
Highbandwidth:Ifweusetheleasedlinesforourcompany
thenthisgivesthehighbandwidth.Thehighbandwidth
increasesthedatatransferratewhichinturnincreasesthe
productivityofourcompany.
WAN(WideAreaNetwork):

105. Classification of Computer Networks
DifferencebetweenLANandWAN:
S.
NO
LAN WAN
1.
LAN stands for Local Area
Network.
Whereas WAN stands for Wide
Area Network.
2.LAN’s ownership is private.
But WAN’s ownership can be
private or public.
3.
The speed of LAN is high(more
than WAN).
While the speed of WAN is
slower than LAN.
4.
The propagation delay is short
in LAN.
Whereas the propagation delay
in WAN is long(longer than
LAN).
5.
There is less congestion in
LAN(local area network).
While there is more congestion
in WAN(Wide Area Network).

106. Classification of Computer Networks
S.
NO
LAN WAN
6.
There is more fault tolerance in
LAN.
While there is less fault
tolerance in WAN.
7.
LAN’s design and maintenance
is easy.
While it’s design and
maintenance is difficult than
LAN.
8.
LAN covers small area i.e. within
the building.
While WAN covers large
geographical area.
9.
LAN operates on the principle of
broadcasting.
While WAN works on the
principle of point to point.
10.
Transmission medium used in
LAN is co-axial or UTP cable.
Whereas WAN uses PSTN or
satellite link as a transmission
or communication medium.
DifferencebetweenLANandWAN:

107. Classification of Computer Networks
DifferencebetweenLAN,MANandWAN:
LAN MAN WAN
LAN stands for local
area network.
MAN stands for
metropolitan area
network.
WAN stands for wide
area network.
LAN’s ownership is
private.
MAN’s ownership can
be private or public.
While WAN also might
not be owned by one
organization.
The transmission
speed of a LAN is high.
While the transmission
speed of a MAN is
average.
Whereas the
transmission speed of
a WAN is low.
The propagation delay
is short in a LAN.
There is a moderate
propagation delay in a
MAN.
Whereas, there is a
long propagation delay
in a WAN.

108. Classification of Computer Networks
DifferencebetweenLAN,MANandWAN:
LAN MAN WAN
There is less
congestion in LAN.
While there is more
congestion in MAN.
Whereas there is more
congestion than MAN
in WAN.
LAN’s design and
maintenance is easy.
While MAN’s design
and maintenance is
difficult than LAN.
Whereas WAN’s design
and maintenance is
also difficult than LAN
as well MAN.
There is more fault
tolerance in LAN.
While there is less fault
tolerance.
In WAN, there is also
less fault tolerance.

109. Classification of Computer Networks

110. Classification of Computer Networks