BROADBANDLAB4: Networking Student's Name Course University Date

This document discusses TCP congestion control, including its meaning, characteristics, examples of CC, and more.

RunningHeadBROADBANDLAB-4: 1
Networking
Student’sName
Course
University
Date

BROADBANDLAB-4 2
Executivesummary
ThetaskisgoingtocoveraboutTCPcongestioncontrol,whichmeansthecontrolofthenetworkcongestion.
ThefollowingtopicsaregoingtobediscussedabriefdescriptionofthemeaningoftermTCPcongestion
avoidance,theessentialcharacteristicsofCCsthatisexploredinthelablikeNewReno,CUBICandVegas,
examplesofCCsandadiscussionoftheyareusedintheinternettoday,thedefaultofTPCcongestion
controlmethod,TCPoptions,calculationofBandwidthDelayProductforthreedifferentscenarios,agraph
ofTCPMetrixvs.timeandthefollowingaretobediscussed;scenarioA,B,andCrepresent,howsockets
sendbufferoccupancy,andcwndvaluesarerelatedtoeachother,howtoobtainsmoothRTTestimates,how
stableRTTestimatesvarywiththebandwidth,howRTTpathaffectcwndgrowthandTCPoptionsthat
werediscussedandagreedonbythegroupsconcerningeachscenario.TCPcongestioncontrol,which
meansTransmissioncontrolprotocolsystemwhichisusedincongestioncontrol.Thesystemcongestion-
avoidancealgorithmisthecongestioncontrolprimarybasisontheinternetwhichisperprinciplefromone
pointtoanother,andthecentralsystem purposeistoserveasaninternethostbutnotthenetwork
specifically.AllofTCP'smeasuredround-tripsdelaysandtimeoutsthatweresetuptothemid-1990swere
generallybasedonlyonthepacketthatwastransmittedlastinthesendbuffer.Nevadaisalargecityof
whichTPCVegasisnamedafter,theround-tripdelaysandsettimeoutsaremeasuredineachpacketthatis
inthetransmitbuffer.TCPNewRenoishelpinginimprovingthetransmissionofTPCRenoduringthe
recoveryfast-face,foreachACKduplicateduringthefastrecoveryisthentakenbacktoTCPNewReno
afterthatanewpacketissentfromthecongestionwindowendthatisusedtofillthetransmitwindow.TPC
CUBICisidentifiedasamoresystematicderivativeandlessaggressiveoftheBIC,windowwhichisa
cubicfunctionoftimethatisfromthelasteventcongestiontotheinflectionpointthatwassetbeforethe
windowevent.TCPcongestion-controlstrategyisthecongestioncontrolmainbasisontheinternetwhichis
perprinciplefromonelocationtoanother,thecongestionavoidancemainpurposeistoserveasaninternet
hostsbutnotthenetworkspecifically;basicallyitusesanalgorithmnetworkcongestion-avoidancewhich
hasthreephaseslikemultiplicativedecreasesystemtogetherwithothersystemslikecongestioncontroland
slowstartphasethatusedinthesuccessofavoidingthenetworkcongestion.

BROADBANDLAB-4 3
Tableofcontent
Introduction 5
Question1 5
DescriptionofthetermTPCcongestioncontrol 5
Essentialcharacteristicsofcongestioncontrol 5
ExamplesofCCsandhowtheyareusedontheinternettoday 6
Question2 6
ThedefaultofTPCcongestioncontrolmethod 6
Question3 7
TCPoptions 7
Lab-basedquestion1 7
CalculationofBandwidthDelayProductforthreedifferentscenarios 7
Lab-basedquestion2 8
AgraphofTCPMetrixvs.time 8
Lab-basedquestion3 9
TCPoptionsagreedoneachscenario 10

BROADBANDLAB-4 4
Conclusion 12
References 15
Appendices 17
Introduction
ThetaskisgoingtocoveraboutTCPcongestioncontrol,whichmeansthecontrolofthenetworkcongestion
(Cardwell etal.2019).Thefollowingtopicsaregoingtobediscussedabriefdescriptionofthemeaningof
thetermTCPcongestionavoidance,theessentialcharacteristicsofCCsthatisexploredinthelablikeNew
Reno,CUBICandVegas,examplesofCCsandadiscussionoftheyareusedintheinternettoday,the
defaultofTPCcongestioncontrolmethod,TCPoptions,calculationofBandwidthDelayProductforthree
differentscenarios,agraphofTCPMetrixvs.timeandthefollowingaretobediscussed;scenarioA,B,and
Crepresent,howsocketssendbufferoccupancy,andcwndvaluesarerelatedtoeachother,howtoobtain
smoothRTTestimates,howstableRTTestimatesvarywiththebandwidth,howRTTpathaffectcwnd
growthandTCPoptionsthatwerediscussedandagreedonbythegroupsconcerningeachscenario
QUESTION1
BriefdescriptionofthemeaningofthetermTCPcongestionavoidance
TCPcongestioncontrol,whichmeansthecontrolofnetworkcongestion.TCPcongestion-avoidancecontrol

BROADBANDLAB-4 5
isthecongestioncontrolmainbasisontheinternetwhichisperprinciplefromonepointtoanother,the
congestioncontrolmainpurposeistoserveasaninternethostbutnotthenetworkspecifically(Cardwell
etal.2016).
EssentialcharacteristicsoftheCCsexploredintheVegas,CUBICandNewReno
a) TCPVegas
AllofTCP'smeasuredround-tripsdelaysandtimeoutsthatweresetuptothemid-1990sweregenerally
basedonlyonthepacketthatwastransmittedlastinthesendbuffer.NevadaisalargecityofwhichTPC
Vegasisnamedafter,theround-tripdelaysandsettimeoutsaremeasuredineachpacketthatisinthe
transmitbuffer(Cardwell etal.,2017).TCPVegasalsouseraisingadditiveinthecongestionwindow,
however,apartfromPeterson'slaboratoryTPCVegaswasnotcommonlyused.IncomparisontoTCP
VegasandTCP,CUBICTCPVegasappearstobethesmootherwhichhasbeenprovenfromdifferentTCP
congestioncontrolalgorithmsstudy.AsadefaultofcongestionmethodofDD-WRT firmwareTCPVegas
wasdeployed(Casoni etal.2015).
b) NewReno
TCPNewRenoisbasicallyhelpinginimprovingthetransmissionofTPCRenoduringtherecoveryfast-
face,foreachACKduplicateduringthefastrecoveryisthentakenbacktoTCPNewRenoafterthatanew
packetissentfromthecongestionwindowendthatisusedtofillthetransmitwindow(Dong etal.,2016).
ThepartialprogressthatismadebyeveryACKinthespacesequenceanewholeispointedoutbyACKas
assumedbythesender,andthenumberbeyondtheACKsequenceissentasthenextpacket.Whenever
thereistransmitbufferprogressthetimertimeoutisresetthishelpstoallowNewRenoinoccupyinglarge
holesorevennumerousgapsinthespacesequence.Duringthelastphaseofcongestionavoidanceofthe
fastrecovery,NewRenosendsnewpacketsduetothismaintenanceofthehighprocessoffillingtheholes
isobservedthroughout.Eveninthecasewheretherearenumerousholesofeachmultiplepackages.Inthe
fastrecoveryperiodofCCs,ahighoutstandingunacknowledgednumberofsequencepacketisrecorded
whenthishappensTPC,therefore,returnstothestateofcongestionavoidance.

BROADBANDLAB-4 6
c) TCPCUBIC
TPCCUBICisconsideredasamoresystematicderivativeandlessaggressiveoftheBIC,windowwhichis
acubicfunctionoftimethatisfromthelasteventcongestiontotheinflectionpointthatwassetbeforethe
windowevent(Wang etal.2015).
ExamplesofCCsandadiscussionoftheyareusedontheinternettoday
TCPcongestion-controlstrategyisthecongestioncontrolmainbasisontheinternetwhichisperprinciple
fromonepointtoanother,thecongestionavoidancemainpurposeistoserveasaninternethostsbutnotthe
networkspecifically;basicallyitusesanalgorithmnetworkcongestion-avoidancewhichhasthreephases
likemultiplicativedecreasesystemtogetherwithothersystemslikecongestioncontrolandslowstartphase
thatusedinthesuccessofavoidingthenetworkcongestion.
CongestionAvoidance
ThecongestionAvoidanceisanexampleofCCsitusedindeterminingthenumberofthebytethatattimes
itcanbeoutstanding.Thesendermaintainsthecongestion;however,theflowcontrolthatissupportedby
thereceivermightbeconfused.Thecongestionavoidanceisusedasameansofstoppingthesenderandthe
receiver'slinkwhichhelpspreventtoomuchtrafficthatmaybecomeanoverload,basicallyusedthe
estimationcalculationofthenumberofcongestionbetweenthereceiverandthesenderlink.
Anindependentvalueismaintainedineveryhostinthecongestionavoidancewhenaconnectionissetup,
whichisasmallmultiplethatissetinformofanMMSthatthelinkisallowed.DuringtheAIMDapproach,
afurthervarianceisdictatedinthecongestionwindow.Thecongestionavoidancetendstokeepongrowing
untilthemomentatimeoutoccurs.Whenatimeouthappenstooccur,thefollowingareobserved:
1. Thecongestionavoidanceisthensetnewlyto1MSS.
2. Slowstartthreshold isthensettoahalfcongestionavoidancesizebeforethetimeoutoccurs.
3. Slowstartphasethenbegins.

BROADBANDLAB-4 7
Slowstart
TheslowstartwhichisanexampleandapartofCCsthatisusedbytheTCPintheconjunctionofother
algorithmsthatisusedtopreventthemoredatasendingthanthatofthenetworkcanhandlethatpreventsthe
congestionnetworkthatmightbecaused.However,thestrategymoreandquiteaggressivedespiteitsname
slowstart,whichismoreaggressivethanthephaseofcongestionavoidance.Thepre-congestionavoidance
thatexistedbeforetheslowstartwasfaster(Jose etal.2015).CongestionWindowsizeinitiallybeginswith
thedeliberatestartstrategyandthereforethecongestionwindowraisebyonereceivedacknowledgmentof
each,bydoublingthewindowsizeeffectivelybyround-tripeachtime.
Additiveincrease/multiplicativedecrease
Theadditiveincrease/multiplicativedecrease(AIMD),whichisapartofthecongestioncontrolstrategy,
whichmeansaclosed-loopcontrolalgorithm.Thisstrategyhelpsinjoininganexponentialreductionandthe
lineargrowthduringtheoccurrenceofthecongestion.TheAIMDisusedinmultipleflowsbywhichthe
congestioncontrolisthen
Convergedinusingcontendedlinksamountsthatareequal.
QUESTION2
ThedefaultofTPCcongestioncontrolmethod
ThedefaultofTPCcongestionavoidancesystemisusedinthefollowingoperatingsystems.
FreeBSD
FreeBSDisanopen-sourceandafreeUnix-likeoperatingsystemthatdependsontheBerkeleySoftware
Distribution(BSD)whichiscommonlybasedontheUNIXresearch.1993FreeBSDfirstversionwas
released,FreeBSDin2005wasoneoftheleadingBSDoperatingsystemopen-source.FreeBSDoperating
systemacquiressomecommonalitieswithLinux;however,theretwodifferences,whichincludelicensing
andscope(Mudassar etal.2018).FreeBSDmaintainsasystemthatiscompletelikethedevicedrivers,

BROADBANDLAB-4 8
userlandutilities,theprojectdeliversakernelandlastlydocumentation,incomparisontoLinux,theyonly
deliverdriversandakernelanddependingonsystemsoftwarewhichwasathirdparty(Heetal.,2016).The
FreeBSDisusedinseveralcaseswhichincludeserverswhichcontainportscollectionwhichFreeBSDis
usedasawebserver,mailserver,DNSserver,router,firewall,andFTPserverandmanyotherapplications,
DesktopandlaptopTheXWindowSystemduetodefaultthatisnotinstalledbuttheFreeBSDport
collectionhasit,Embeddedsystem,NetworkingFreeBSDisbasicallybasedonTCPimplementationwhich
alsosupportsWi-Fi,IPsec,IPv6andSCTP,StorageFreeBSDacquiresdifferentuniquestoragefeaturesthat
helptoprotectsoftupdates,inaddition,thestructuretwoframeworksthatareusedintheencryptiondata
whichincludesGeliandGBDE,Securitythefabrichassomeuniquefeatures
Thatarerelatedinsecuritylikeaccesscontrollists(ACLs),extendedfilesystemattributes,fine-grained
capabilities,mandatoryaccesscontrols(MAC)andsecurityeventauditingandlastlyitsportabilityithas
beendesignedinawayeasilyportable(KimandKnösche2016).
MacOSX
MacOSXfirstversionmainpurposewastotransitionproducts,aninterfacethatwasfeaturedtoresemble
theMacOSclassic;however,thesystemwasnevercompatiblewiththeoldersystemthatwassoftware
designed.ThereleaseofMacOSXconsumerwhichincludedthemorebackwardcompatibility.The
applicationcanbewrittengenerallyviatheAPICarbon.However,manyotherapplicationscanbeoperated
directlyinaperfectenvironmentthathasreducedperformance(Trabelsi,2016).Theappwaslaunchedin
2001thatwasaccompaniedbyMacOSX10.0.TheMacOSXhasreceivedlotsofpraiseduetoitsglossy
andsophisticatedAquainterface;however,theirseveralcriticismsreceivedduetotheirsluggish
performance(PapadimitriouandMoussiades2016).
LinuxKernel
LinusTorvaldscreatedtheoperatingsystemin1991.TheLinuxKernelisanopenandfreesource,Unix-
like,andmonolithicoperatingsystemkernel(Alrshah etal.2015).TheLinuxKernelisanapplicationthatis
usedaspartofanoperatingsystemwhichisbasedonthekernelandwasavailablebothincomputers

BROADBANDLAB-4 9
systemsthatweretraditionalliketheserversandpersonalcomputersthatismostlyusedinLinux
distributionformandinotherdifferentembeddeddeviceslikethewirelessaccesspoints,PBXes,FTA
receivers,PVRs,smartTVs,NASappliancesandset-topboxes.In2017November,itwasdiscoveredthat
intheworldthemostpowerfulcomputersarerunbyLinuxisabout500,otherexamplesofLinuxusersis
theAndroidoperationthatisusedinsmartphones,watchesandtabletcomputers(Lin etal.,2018).
WindowXP,7,10
In2001WindowsXPwascreatedwhichwasdesigneddifferentlyandwasmoreattractivetothecustomers
andconsistedofanewoperatingsystemwhichisestablisheddependingonthewindow2000kernelthat
providedafriendlierenvironmenttotheuseraspercomparedtoinitialone.WindowXPconsistsoftwo
differenttypes,whichincludestheprofessionalandhome(Peng etal.2015).TheMicrosoftaimsatthe
portabilityofbotheditionswhichcomprisesofplayandplugfeaturesthatareusedduringtheconnectionof
wirelessnetworks.
QUESTION3
TCPoptions
TheonlytimetheTCPoptionsanalysisneedtoappearisonlywhentheinitialSYNN/ACKandSYNpartof
theperformanceof3-way-handshakeofTCPthatisusedtogiveanexactlinkevenbeforetransferringany
data.DuringthesessionofTCP,otheroptionsmaybeusedaccordingtothechoiceoftheuser.Itisvery
vitalalsototakenotethatTCPoptionmayrequiresomespacehencemayoccupyattheTCPheadersend,
andinlength,itconsistsofmultiplesof8bitsMaximumsegmentsize(MMS)andWindowscalingaretwo
examplesofTCP.
SMMS
Thesmallmaximumsegmentsizeismostlyusedwhenthereisaconnectionbetweentwopeoplewhoare
tryingtocommunicateorpasssomeinformation.DuringtheSYN/ACKandSYNpartoftheperformanceof
3-way-handshakeofTCPthatisusedtogiveanexactlinkevenbeforetransferringanydataMMSoptionis

BROADBANDLAB-4 10
theonlyavailableoption.Thelengthofmaximumsegmentsizerequiresaspaceof4byteswhichis32bits,
MTUisalsoacommontermthatmeansMaximumtransferUnitthisisassistedinitsdefinitionbytheMMS
thatisusedinthenetwork(Sung,2015).TheMMScomprisesofthedatasegment,andontheotherside
MTUconsistsofMSS,TCPheaderandtheIPheader,It’salsorecommendedfortheusertoidentifythe
terminologiescorrectlythatareasperthelevelofeachOSImodel.Thelayerfourisknownasasegment
whichconsistsoftheDataandtheTCPHeader,andlayerthreeisknownasIPDatagramwhichconsistsof
thepartandtheIPHeader(JagadeeswaranandAnnamalaisami,2015)
Windowscaling
WindowscalingisgenerallytheextensionoftheWindowsizeflagthisisduetoitspossiblemost
significantvaluewhich65535byteswhichisequalto64kb,forthecreationofWindowscalingwasdueto
theneedofanamplespacebecauseoftheriseofthe1Gigwhoppingvalue.ThevalueofWindowscaling
optionscanbeincreasedtoamaximumof30bits.Thepurposeofwindowscalingcreationwasbecauseof
high-bandwidthandhigh-latency(Wangetal.2017).
Theinterpretationofthediagramisthat64kbsisthemaximumWindowthatiscurrentlybeingusedanddue
toitshigh-bandwidthandhigh-latencysometimeisrequiredforthepackettoreachitsdestinationthatis
basicallytheBhost,whilefortheAhostduetothe64kbsithasstoppedthetransmissionthatisbeingsent
andnoacknowledgmenthasnotbeenreceived(Mehdizadehetal.,2018).However,ifthevalueislargethe
windowscalinginraisedto256kb
LABBASEDQUESTION1
CalculationofthebandwidthdelayproductsofscenarioA,BandC Bandwidth
DelayProduct=bandwidth(bitspersec)*time(inseconds)(Fuxaetal.2017)

BROADBANDLAB-4 11
Scenario Bandwidth PathRTT
A 5Mbs 100ms
B 512Kbs 40ms
C 5Mbs 40ms
ScenarioA
5Mbs*1000000bits=5000000bits
5000000bits*0.1s=500000bandwithdelayproduct
ScenarioB
512Kbs*1000bits-512000bits
512000bits*0.04s=20480bandwidthdelayproduct
ScenarioC
5Mbs*1000000bits=5000000bits
5000000bits*0.04s=200000bandwidthdelayproduct
LABBASEDQUESTION2
TCPmatricvs.time
ScenarioArepresentsPCSVEGAS
AllofTCP’smeasuredround-tripsdelaysandtimeoutsthatweresetuptothemid-1990sweregenerally
basedonlyonthepacketthatwastransmittedlastinthetransmitbuffer.Nevadaisalargecityofwhich
TPCVegasisnamedafter,theround-tripdelaysandsettimeoutsaremeasuredineachpacketthatisinthe

BROADBANDLAB-4 12
transmitbuffer.TCPVegasalsouseraisingadditiveinthecongestionwindow,however,apartfrom
Peterson'slaboratoryTPCVegaswasnotcommonlyused.IncomparisontoTCPVegasandTCP,CUBIC
TCPVegasappearstobethesmootherwhichhasbeenprovenfromdifferentTCPcongestioncontrol
algorithmsstudy.
ScenarioBrepresentsNewReno TCP
NewRenoisbasicallyhelpinginimprovingthetransmissionofTPCRenoduringtherecoveryfast-face,for
eachACKduplicateduringthefastrecoveryisthenreturnedtoTCPNewRenoafterthatanewpacketis
sentfromthecongestionwindowendthatisusedtofillthetransmitwindow(Dong etal.,2016).Thepartial
progressthatismadebyeveryACKinthespacesequenceanewholeispointedoutbyACKasassumedby
thesender,andthenumberbeyondtheACKsequenceissentasthenextpacket.Wheneverthereistransmit
bufferprogressthetimertimeoutisresetthishelpstoallowNewRenoinfillinglargeholesorevenmultiple
gapsinthespacesequence.Attheendofthecongestionwindowduringthefastrecovery,NewRenosends
newpacketsduetothismaintenanceofhighthroughputisobservedintheprocessofhole-fillingEveninthe
casewheretherearemultipleholesofeachmanypackages.Duringthefastrecoveryoffice,ahigh
outstandingunacknowledgednumberofsequencepacketisrecordedwhenthishappensTPC,therefore,
returnstothestateofcongestionavoidance.
ScenarioCrepresentsCUBIC
TPCCUBICisconsideredasamoresystematicderivativeandlessaggressiveoftheBIC,windowwhichis
acubicfunctionoftimethatisfromthelasteventcongestiontotheinflectionpointthatwassetbeforethe
windowevent
LABBASEDQUESTION3
TheTPCoptionsnegotiatedineachscenario

BROADBANDLAB-4 13
Inthescenario,AandCwindowsellingisusedsinceitisfastandhasasignificantvaluethatcanbeusedto
operatelargesystemswhileforscenarioBmulti-segmentsizewasusedthisisbecauseitdoesnotrequire
hugespace.
Conclusion
ThetaskhascoveredaboutTCPcongestioncontrol,whichmeansTransmissioncontrolprotocolcongestion
control.ThefollowingtopicshavebeendiscussedabriefdescriptionofthemeaningoftermTCP
congestioncontrol,thebasiccharacteristicsofcongestioncontrolthatisexploredinthelablikeNewReno,
CUBICandVegas,examplesofCCsandadiscussionoftheyareusedontheinternettoday,thedefaultof
TPCcongestioncontrolmethod,TCPoptions,calculationofBandwidthDelayProductforthreedifferent
scenarios,agraphofTCPMetrixvs.timeandthefollowingaretobediscussed;scenarioA,B,andC
represent,howsocketssendbufferoccupancy,andcwndvaluesarerelatedtoeachother,howtoobtain
smoothRTTestimates,howsmoothRTTestimatesvarywiththebandwidth,howRTTpathaffectcwnd
growthandTCPoptionsthatwerediscussedandagreedonbythegroupsconcerningeachscenario.TCP
congestioncontrol,whichmeansTransmissioncontrolprotocolsystemwhichisusedincongestioncontrol.
Thesystemcongestion-avoidancealgorithmisthecongestioncontrolprimarybasisontheinternetwhichis
perprinciplefromonepointtoanother,thecongestioncontrolmainpurposeistoserveasaninternethost
butnotthenetworkspecifically.AllofTCP'smeasuredround-tripsdelaysandtimeoutsthatweresetupto
themid-1990sweregenerallybasedonlyonthepacketthatwastransmittedlastinthetransmitbuffer.
NevadaisalargecityofwhichTPCVegasisnamedafter,theround-tripdelaysandsettimeoutsare
measuredineachpacketthatisinthetransmitbuffer.TCPNewRenoishelpinginimprovingthe
transmissionofTPCRenoduringtherecoveryfast-face,foreachACKduplicateduringthefastrecoveryis
thenreturnedtoTCPNewRenoafterthatanewpacketissentfromthecongestionwindowendthatisused
tofillthetransmitwindow.TPCCUBICisconsideredasamoresystematicderivativeandlessaggressiveof
theBIC,windowwhichisacubicfunctionoftimethatisfromthelasteventcongestiontotheinflection
pointthatwassetbeforethewindowevent.TCPcongestion-controlstrategyisthecongestioncontrolmain
basisontheinternetwhichisperprinciplefromonepointtoanother,thecongestionavoidancemain

BROADBANDLAB-4 14
purposeistoserveasaninternethostsbutnotthenetworkspecifically;basicallyitusesanalgorithm
networkcongestion-avoidancewhichhasthreephaseslikemultiplicativedecreasesystemtogetherwith
othersystemslikecongestioncontrolandslowstartphasethatusedinthesuccessofavoidingthenetwork
congestion.ThecongestionwindowisanexampleofCCsitusedindeterminingthenumberofthebytes
thatattimesitcanbeoutstanding.Thesendermaintainsthecongestionwindow;however,thesliding
windowthatismaintainedbythereceivermightbeconfused.Thecongestionwindowisusedasameansof
stoppingthesenderandthereceiver'slinkwhichhelpspreventtoomuchtrafficthatmaybecomean
overload,basicallyusedtheestimationcalculationofthenumberofcongestionbetweenthereceiverandthe
senderlink.TheslowstartwhichisanexampleandapartofCCsthatisusedbytheTCPintheconjunction
ofotheralgorithmsthatisusedtopreventthemoredatasendingthanthatofthenetworkcanhandlethat
preventsthecongestionnetworkthatmightbecaused.Theadditiveincrease/multiplicativedecrease
(AIMD),whichisapartofthecongestioncontrolstrategy,whichmeansaclosed-loopcontrolalgorithm.
Thisstrategyhelpsinjoiningexponentialreductionsandlineargrowthduringtheoccurrenceofcongestion.
TheAIMDisusedinmultipleflowsbywhichthecongestioncontrolisthenconvergedinusingcontended
linksamountsthatareequalFreeBSDisanopen-sourceandafreeUnix-likeoperatingsystemthatdepends
ontheBerkeleySoftwareDistribution(BSD)whichiscommonlybasedontheUNIXresearch.1993
FreeBSDfirstversionwasreleased,FreeBSDin2005wasoneoftheleadingBSDoperatingsystemopen-
source.FreeBSDoperatingsystemacquiressomecommonalitieswithLinux;however,theretwo
differences,whichincludeslicensingandscope.FreeBSDmaintainsasystemthatiscompletelikethe
devicedrivers,userlandutilities,theprojectdeliversakernelandlastlydocumentation,incomparisonto
Linux,theyonlydeliverdriversandakernelanddependingonsystemsoftwarewhichwasathirdparty.
MacOSXfirstversionmainpurposewastotransitionproducts,aninterfacethatwasfeaturedtoresemble
theMacOSclassic;however,thesystemwasnevercompatiblewiththeoldersystemthatwassoftware
designed.Inthescenario,AandCwindowsellingisusedsinceitisfastandhasalargevaluethatcanbe
usedtooperatelargesystemswhileforscenarioBmulti-segmentsizewasusedthisisbecauseitdoesnot
requirehugespace.

BROADBANDLAB-4 15
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Appendices.

BROADBANDLAB-4 18