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Cisco press qos for IP MPLS networks jun 2006 ISBN 1587052334

QoSforIP/MPLSNetworks
BySantiagoAlvarez
...............................................
Publisher:CiscoPress
PubDate:June02,2006
PrintISBN-10:1-58705-233-4
PrintISBN-13:978-1-58705-233-0
Pages:336

TableofContents|Index

ThecomprehensiveguidetoimplementingQoSinmultiservicenetworksusingIP/MPLS
UnderstandthetechnologycomponentsofimplementingQoSinamultiservice
network
LearnhowtoconfiguretheMPLSQoSfunctionalityinCiscoIOS--configurationdetails
helpyoudeployQoSinyournetwork
DesignoptimalnetworkswithconfidencethroughknowledgeofmultipleQoSdesign
options
UnderstandthemarketpotentialofservicedifferentiationusingQoS
QualityofService(QoS)playsakeyroleintheimplementationofmultiserviceand
convergednetworks.Industryeffortstoachieveconvergencehavegeneratedaneedfor

increasedlevelsoftrafficdifferentiation.AnarrayofQoSrequirementsneedtobemetto
supportdistinctapplications(e.g.voice,video,anddata)andmultiplenetworkservices
(e.g.IP,Ethernet,ATM)onasingleconverged,multiservicenetwork.Therefore,QoShas
becomeanintegralpartofanmultiservice,convergednetworkandservice
implementation.QoSforIP/MPLSNetworksoffersnetworkarchitectsandengineersa
singlesourceofinformationforthedesign,deployment,andimplementationofQoSenabledservicesonanMPLSnetworkusingCiscoIOS.Readerswillgainknowledgeofthe
technologybehindMPLSQoSandrelatedtechnologiesandwilllearnthedifferentdesign
optionsavailabletobuildamultiserviceMPLSnetwork.Thebookcoversindetailthe
behaviorandconfigurationoftherichMPLSQoSfunctionalityinCiscoIOS.Itisasolid
referenceofworkingconfigurationexamples,butdoesnotintendtobeacommand
referenceonthesubject.


QoSforIP/MPLSNetworks
BySantiagoAlvarez
...............................................
Publisher:CiscoPress
PubDate:June02,2006
PrintISBN-10:1-58705-233-4
PrintISBN-13:978-1-58705-233-0
Pages:336

TableofContents|Index










































Copyright
AbouttheAuthor
AbouttheTechnicalReviewers
Acknowledgments
IconsUsedinThisBook
Foreword
Introduction
Chapter1.QoSTechnologyOverview
IPQoSArchitectures
MPLSSupportforIntServ
MPLSSupportforDiffServ
Traffic-ManagementMechanisms
QoSSignaling
Summary
References
Chapter2.MPLSTETechnologyOverview
MPLSTEIntroduction
BasicOperationofMPLSTE
DiffServ-AwareTrafficEngineering
FastReroute
Summary
References
Chapter3.CiscoQoS
CiscoQoSBehavioralModel
























































ModularQoSCommand-LineInterface
Summary
References
Chapter4.CiscoMPLSTrafficEngineering
BasicOperationofMPLSTE
DiffServ-AwareTrafficEngineering(DS-TE)
FastReroute(FRR)
Summary
References
Chapter5.BackboneInfrastructure
BackbonePerformance
LatencyVersusLinkUtilization
ReferenceNetwork
QoSDesignAlternatives
DiffServBackbonewithMPLSTE
Summary
References
AppendixA.CommandReferenceforCiscoMPLSTrafficEngineeringandRSVP
MPLSTECommands
EXECCommands
showCommands
clearCommands
debugCommands
RSVPCommands
showCommands
clearCommands
debugCommands
Index


Copyright
QoSforIP/MPLSNetworks
SantiagoAlvarez
Copyright©2006CiscoSystems,Inc.
Publishedby:
CiscoPress
800East96thStreet
Indianapolis,IN46240USA
Allrightsreserved.Nopartofthisbookmaybereproducedor
transmittedinanyformorbyanymeans,electronicor
mechanical,includingphotocopying,recording,orbyany
informationstorageandretrievalsystem,withoutwritten
permissionfromthepublisher,exceptfortheinclusionofbrief
quotationsinareview.
PrintedintheUnitedStatesofAmerica1234567890
FirstPrintingJune2006
LibraryofCongressCataloging-inPublicationNumber:2004117089

TrademarkAcknowledgments
Alltermsmentionedinthisbookthatareknowntobe
trademarksorservicemarkshavebeenappropriately
capitalized.CiscoPressorCiscoSystems,Inc.cannotattestto
theaccuracyofthisinformation.Useofaterminthisbook
shouldnotberegardedasaffectingthevalidityofany
trademarkorservicemark.


WarningandDisclaimer
Thisbookisdesignedtoprovideinformationaboutqualityof
serviceinIP/MPLSnetworksusingCiscoIOSandCiscoIOSXR.
Everyefforthasbeenmadetomakethisbookascompleteand
asaccurateaspossible,butnowarrantyorfitnessisimplied.
Theinformationisprovidedonan"asis"basis.Theauthors,
CiscoPress,andCiscoSystems,Inc.shallhaveneitherliability
norresponsibilitytoanypersonorentitywithrespecttoany
lossordamagesarisingfromtheinformationcontainedinthis
bookorfromtheuseofthediscsorprogramsthatmay
accompanyit.
Theopinionsexpressedinthisbookbelongtotheauthorand
arenotnecessarilythoseofCiscoSystems,Inc.

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Thanksforwithstandinglong,longworkinghours.


AbouttheAuthor
SantiagoAlvarez,CCIENo.3621,isatechnicalmarketing
engineeringforCiscoSystemsworkingonMPLSandQoSsince
2000.HejoinedCiscointheblazingdaysof1997.Priorto
Cisco,SantiagoworkedinsoftwaredevelopmentforLucent
Technologies.Hehasbeeninvolvedwithcomputernetworking
since1991.SantiagoisafrequentspeakeratCiscoNetworkers
andaperiodiccontributortoCiscoPacketMagazine.Heholdsa
bachelorofsciencedegreeincomputersciencefromEAFIT
University,amasterofSciencedegreeincomputersciencefrom
ColoradoStateUniversity,andamasterofsciencein
telecommunicationsfromtheUniversityofColoradoatBoulder.
Outsidework,heenjoystheoutdoors,finefood,andexploring
theworldasanindependenttraveler.Hecanbereachedat
saalvare@cisco.com.




AbouttheTechnicalReviewers
MarkGalloisasystemsengineeringmanageratCisco
Systemswithinthechannelsorganization.Hehasledseveral
engineeringgroupsresponsibleforpositioninganddelivering
Ciscoend-to-endsystems,aswellasdesigningand
implementingenterpriseLANsandinternationalIPnetworks.He
hasaB.S.degreeinelectricalengineeringfromtheUniversity
ofPittsburghandholdsCiscoCCNPandCCDPcertifications.
MarkresidesinnorthernVirginiawithhiswife,Betsy,andson,
Paul.
RaymondZhangisaseniornetworkarchitectforBTInfonetin
theareasofGlobalIPbackboneinfrastructure,routing
architecturedesign,planning,anditsevolutions.Currently,his
mainareasofinterestincludelarge-scalebackbonerouting,
trafficengineering,performanceandtrafficstatisticalanalysis,
andMPLS-relatedtechnologies(includinginterdomaintraffic
engineering,GMPLS,metroEthernet,Diffserve,IPv6,and
Multicast).RaymondparticipatesinseveralIETFdraftsrelating
toMPLS,BGP-basedMPLSVPN,Inter-ASTE,and,more
recently,PCE-basedwork.




Acknowledgments
IwouldliketogivespecialthankstoBobOlsenandSandeep
Bajajforsharingtheirtechnicalexpertisethroughsomany
years.Theyhavepatientlytoleratedmyconstantinterruptions
andhaveprovidedusefulinsightondifferenttopicsincludedin
thebook.
Specialthankstothereviewers,MarkGalloandRaymond
Zhang.Iappreciateyourdetailedcomments.Iamtoblamefor
anyremaininginaccuraciesoromissions.
BigthankstoBruceDavie,whoseresponsivenessatkeypoints
encouragedmetopersistinmygoal.Ihighlyregardhis
unusualabilitytoabstractcomplexityandclearlyillustratethe
essenceofintricatetechnologyconcepts.Muchofhisworkhas
directlyandindirectlyinfluencedthecontentofthisbook.
Similarly,IextendmygratitudetoFranÁoisLeFaucheurand
JeanPhilippeVasseur.Theyhavehadthepatiencetodiscuss
withmemanyaspectsofthesetechnologiesinnumerous
occasions.Merci!
ThankstoRameshUppiliforcontributingtothepresentationof
keytopicsinmultipleways.
IalsowanttothankRakeshGandi,PrashanthYelandur,Ashish
Savla,BobbyKaligotla,LawrenceWobker,AshokGanesan,Jay
Thontakudi,andScottYowforfacilitatingthediscussionofCisco
IOSXRinthisbook.
SpecialthankstotheCiscoPressteam:JohnKane,Chris
Cleveland,JillBatistick,SanDeePhillips,andElizabeth
Peterson.Ireallyappreciateyourattentiontodetailand
extraordinarypatiencewithme.IwishJohnthebestinhisnew
endeavors.


Finally,ifyouhavereadthisfarinsearchofyourname,this
paragraphisforyou.Ihavetoacknowledgethatnumerous
individualscontributedthroughinsightfuldiscussions.They
unhappilyormaybehappilyremainanonymous.Thanks!




IconsUsedinThisBook
[Viewfullsizeimage]

CommandSyntaxConventions
Theconventionsusedtopresentcommandsyntaxinthisbook
arethesameconventionsusedintheIOSCommandReference.
TheCommandReferencedescribestheseconventionsas
follows:
Boldfaceindicatescommandsandkeywordsthatare
enteredliterallyasshown.Inactualconfigurationexamples
andoutput(notgeneralcommandsyntax),boldface
indicatescommandsthataremanuallyinputbytheuser
(suchasashowcommand).
Italicsindicateargumentsforwhichyousupplyactual


values.
Verticalbars(|)separatealternative,mutuallyexclusive
elements.Note,however,thattheverticalbar(pipe
operand)isalsousedtofiltercommand-lineinterface
commandoutput;inthatscenario,theoperand(|)precedes
thebegin,exclude,orincludekeywords,whicharethen
followedbyaregularexpression.
Squarebrackets[]indicateoptionalelements.
Braces{}indicatearequiredchoice.
Braceswithinbrackets[{}]indicatearequiredchoice
withinanoptionalelement.




Foreword
Thephrase"IPQoS"wasformanyyearsconsideredan
oxymoron.Indeed,muchofthesuccessoftheIParchitecture
couldbetracedtoitsadoptionofa"besteffort"servicemodel,
enablingIPtorunoverjustaboutanyunderlyingnetwork
technology.Besteffortservice,however,isdefinedbyalackof
assurancethatpacketswillbedeliveredinatimelymanner,or
evendeliveredatall.Suchaservicemodellimitsthepotential
ofIPnetworkstosupportapplicationsthatdemandtimely
packetdelivery,suchasinteractivetelephonyandmultimedia
applications.
Asfarbackas1979,therewereproposalstoextendtheIP
servicemodeltosupportapplicationswithstrongerQoS
requirements.However,thisremainedaresearchtopicuntilthe
early1990s.Bythatpoint,theideaofconvergencecarrying
manyapplicationswithdiverseQoSneedsonasingle
networkwasgainingcurrency,althoughtheword"convergence"
wouldnotbecomeabuzzwordforseveralyears.ATMwas
widelyexpectedtobethepacketswitchingtechnologythat
wouldenablethisconvergence,butaconcertedefforttoadd
QoStoIPwasalsogettingunderway.Theseminal1992paper
byClark,Shenker,andZhangonsupportofreal-time
applicationsintheInternetputaseriousstakeinthegroundfor
IPQoS,andworkattheIETFtostandardizeasetofIPQoS
mechanismsbeganshortlythereafter.TheIntegratedServices
architectureandResourceReservationProtocolresulted,and
theDifferentiatedServicesarchitecturefollowed.
AnothertechnicaldevelopmentwithbigimplicationsforIPQoS
wasMultiprotocolLabelSwitching,whichgrewoutofworkon
TagSwitchingatCiscobegunin1996.Therewasconsiderable
confusionaboutexactlywhatimpactMPLSwouldhaveonIP
QoS,inpartbecauseoftheresemblancesbetweenMPLSand


ATM,whichhaditsownQoSmodel.Inreality,thebiggestsingle
effectMPLShadonQoSwastoaddanothertooltotheQoS
toolbox,intheformoftrafficengineeringwithconstraint-based
routing.ItisforthisreasonmorethananyotherthatMPLSand
QoSdeservetobecoveredinasinglebook.
Whichbringsustothecurrentvolume.IPQoScannowbe
consideredamaturetechnology,notjustsomethingforthe
bleedingedge.Itisalsonotoriouslycomplextounderstandand
toconfigurecorrectly.Someofthiscomplexityisintrinsic;some
isanaccidentofhistory.Ontheintrinsicside,understanding
QoSishardbecauseitrequirestheabilitytooperateatmany
differentlevelsofabstraction.Oneneedstounderstandthe
highlevelQoSarchitectures,tohaveabehavioralmodelofQoS
featuresinsidearouter,toknowhowthosefeaturesmapontoa
particularpieceofhardware,andtounderstandtheCLIthatis
usedtocontrolthosefeatures.Thisiswherethisbooksets
itselfapartfromthepackofQoSbooks.SomecoverQoS
architectureandIETFstandards.Someprovideinformationon
CLIcommands.ButthisistheonlybookI'vefoundthatwalks
thereaderthroughthelevelsofabstractionfromhighlevel
architecturetolowlevelCLI,withaclearexplanationofthe
abstractQoSbehaviormodelthatallrouterssupportproviding
thebridgebetweenthelevels.Byreadingthisbook,youwill
understandboththebigpictureofQoSandthedetails
necessarytodeployitinarealnetwork.
AnotherfactorthatmadeQoSdifficulttomanageinthepast
wasasomewhatadhocapproachtoitsimplementation.
Combinationsoffeaturesweresometimesimplementedina
monolithicway,andinconsistencyacrossplatformswasthe
norm.Thissituationhasimprovedmassivelyinrecentyears,
notablywiththeadoptionoftheModularQoSCLIacrossmost
oftheCiscoproductline.Thus,QoSdeploymentismuchmore
straightfowardthanitoncewas,andthisbook'stimely
coverageoftheMQCanditsunderlyingbehavioralmodelwill
makeiteveneasier.


Manyreadersmaybetemptedtojumpstraighttothelast
chapter'sguidanceonhowtodesignanddeployaQoSstrategy
inabackbonenetwork.Santiago'sextensivereal-world
deploymentexperiencecertainlymakesthischapterespecially
valuable.However,theprecedingfourchaptersaretheones
thatwillprovideyouwithafundamentalunderstandingofQoS.
Thus,ratherthanblindlyfollowingaQoS"recipe,"you'llbeable
tomaketherightdesigndecisionstomeettheneedsofyour
ownapplicationsandcustomers.Ifyoureallywantto
understandQoSfully,thisisthebooktoread,fromstartto
finish.
BruceDavie
CiscoFellow




Introduction
Themotivationbehindthisbookisthecontinuedinterestinthe
implementationofqualityofservice(QoS)inIP/MPLSnetworks.
QoSarisesasakeyrequirementforthesenetworks,which
havebecomethepreferredtechnologyplatformforbuilding
convergednetworksthatsupportmultipleservices.Thetopic
canbeoneofthemostcomplexaspectsofthenetworkdesign,
implementation,andoperation.Despitetheimportanceofand
interestinthistopic,nootherCiscoPresstitleprovidesa
detaileddiscussionofthissubject.Asignificantamountofthe
contentofthisbookalsoappliestopureIPnetworksthatdonot
haveimmediateplanstomigratetoafullIP/MPLSnetwork.
ThismaterialcoversbothQoSandMultiprotocolLabelSwitching
TrafficEngineering(MPLSTE).Inparticular,itcoversMPLSTE
asatechnologythatcomplementstraditionalQoStechnologies.
MPLSTEcanbeaninstrumentaltooltoimprovetheQoS
guaranteesthatanIP/MPLSnetworkoffers.Assuch,itcan
contributetoimprovingbothnetworkperformanceand
availability.However,thisbookprovidesaconcisediscussionof
MPLSTE.Thosereadersinterestedinfurtherinformationshould
consulttheCiscoPresstitleTrafficEngineeringwithMPLS
Thebooktakesthepointofviewofthoseindividuals
responsiblefortheIP/MPLSnetwork.OtherCiscoPresstitles
describethedetailsoftheQoSimplementationforthose
devicesreceivingtheservicesthatthenetworkoffers.
YoushouldhaveabasicunderstandingofbothIPandMPLSto
obtainthemostbenefitfromthisbook.Thatunderstanding
shouldincludebasicIPaddressingandrouting,alongwiththe
basicsofMPLSforwarding.However,thebookprovidesa
technologyoverviewofQoSandMPLSTEtohelpthosewith
lessexposuretothesetechnologiesortoserveasa
review/referencetothosemorefamiliarwiththosetopics.


Thisbooktouchesabroadtopicanddoesnotpretendto
addressallQoSaspectsofinterest.YoucanexpectfutureCisco
Pressbookstocoverimportantareas,includingthefollowing:
ImplementationofQoSforspecificservices(forinstance,
IP,Ethernet,ATM)
QoSmanagement(includingmonitoringandprovisioning)
InterproviderQoS
Visitthisbook'swebsite,
http://www.ciscopress.com/title/1587052334,forfurther
information.

WhoShouldReadThisBook?
Thisbook'sprimaryaudienceisthetechnicalstaffofthose
organizationsbuildingIP/MPLSnetworksasaninfrastructureto
providemultipleservices.Thematerialincludestechnology,
configuration,andoperationaldetailstohelpinthedesign,
implementation,andoperationofQoSinIP/MPLSnetworks.
Serviceprovidersareaprimeexampleoftheorganizationsthat
thisbooktargets.However,governmentagencies,educational
institutions,andlargeenterprisespursuingIP/MPLSwillfindthe
materialequallyuseful.
Asecondaryaudienceforthisbookisthoseindividualsin
chargeofservicedefinitionorthoseindividualssubscribingto
networkservices.Bothtypescanbenefitfromabetter
understandingofthedifferentiationcapabilitiesthatIP/MPLS
networkscanoffer.

HowThisBookIsOrganized


Althoughthisbookcouldbereadcovertocover,itisdesigned
tobeflexibleandallowyoutoeasilymovebetweenchapters
andsectionsofchapterstocoverjustthematerialthatyou
needmoreworkwith.Thecontentisroughlydividedintothree
parts:
Chapters1and2provideatechnologyoverview.
Chapters3and4discussCiscoimplemenation.
Chapter5coversdifferentbackbonedesignoptions.
Hereisabriefsynopsisofeachchapter:
Chapter1,"QoSTechnologyOverview"Thischapter
providesareviewofQoStechnologyforIPandIP/MPLS
networks.ThechapterinitiallydiscussestheIPQoS
architecturesandhowtheyapplytoMPLS.Multiplesections
elaborateonMPLSsupportforDifferentiatedServices
(DiffServ),includingadetaileddiscussiononEXP-inferred-class
linkswitchedpath(E-LSP),Label-inferred-classLSP(LLSP),and
DiffServtunnelingmodels(pipe,shortpipe,anduniform).This
dicussionleadsintoasummaryoftraffic-management
mechanismswithadetailedlookattrafficpolicing,traffic
shaping,trafficscheduling,activequeuemanangemt,andso
on.ThechapteralsodiscussesQoSsignalingwithafocuson
theResourceReservationProtocol(RSVP).
Chapter2,"MPLSTETechnologyOverview"Thischapter
reviewsthebasicoperationofthistechnologywithitsDiffServ
extensionsandapplicabilityasatraffic-protectionalternative.
Thisreviewelaboratesontheconceptsofcontraint-based
routing,DiffServ-awareTrafficEngineering(DS-TE)andfast
reroute(FRR)(includinglink,shared-risklinkgroup,andnode
protection).


Chapter3,"CiscoQoS"ThischaptercoverstheCiscoQoS
behavioralmodelandthemodularQoScommand-lineinterface
(MCQ).Thechapterabstractstheplatformspecificstofacilitate
theunderstandingofCiscoQoSandprovidesacomplete
referenceoftheconfigurationcommands.Inaddition,the
chapterincludesnumerousexamplestoillustratethe
configurationandverificationofdifferenttraffic-management
mechanismsinCiscoIOSandCiscoIOSXR.Thismaterialis
equiallyrelevanttoIPandIP/MPLSnetworks.
Chapter4,"CiscoMPLSTrafficEngineering"Thischapter
presentsCiscoimplementationofMPLSTrafficEngineeringin
bothCiscoIOSandCiscoIOSXR.Itincludesmultiple
configurationandverificationexamplesillustratingthe
implementationofbasicMPLSTE,DS-TE,andFRR.
Chapter5,"BackboneInfrastructure"Thischapterdiscusses
thebackboneperformancerequirementsandthedifferent
designoptions.Thechapterreviewsdifferentdesigns,ranging
fromabest-effortbackbonetothemostelaboratescenarios
combiningDiffServ,DS-TE,andFRR.Numerousconfiguration
examplesillustratetheirimplementationusingCiscoIOSand
CiscoIOSXR.


Chapter1.QoSTechnologyOverview
Inthischapter,youreviewthefollowingtopics:
IPQoSArchitectures
MPLSSupportforIntServ
MPLSSupportforDiffServ
Traffic-ManagementMechanisms
QoSSignaling
Thischapterprovidesareviewofthekeytechnology
componentsofqualityofservice(QoS)inIP/MPLSnetworks.
ThisreviewdiscussestheIntServandDiffServarchitectures
includingtheirrelationshipwithMPLS.Thechaptercoversthe
trafficmanagementmechanismsthatenableQoS
implementationandreviewsdifferentQoSsignalingalternatives
inIP/MPLSwithaspecialfocusonRSVPprotocol.
Thisbookassumesthatyouarealreadyfamiliarwiththebasic
conceptsbehindthesetopics.Youshouldalsobefamiliarwith
thebasicsofMultiprotocolLabelSwitching(MPLS)ingeneral.
ThischapterandChapter2,"MPLSTETechnologyOverview,"
serveasatechnologyreviewandquickreferenceforlater
content.Chapter3,"CiscoQoS,"coversthespecificsonCisco
implementationofQoStechnology.The"References"sectionat
theendofthischapterlistssourcesofadditionalinformationon
thetopicsthatthischaptercovers.


IPQoSArchitectures
Originally,IPwasspecifiedabest-effortprotocol.Oneofthe
implicationsofthisservicedefinitionwasthatthenetwork
wouldattempttodeliverthetraffictoitsdestinationinthe
shortesttimepossible.However,thenetworkwouldprovideno
guaranteeofachievingit.
Thisservicedefinitionprovedsuccessfulduringtheearly
Internetyears,whendataapplicationsconstitutedthebulkof
Internettraffic.Generally,theseapplicationsusedTCPand
thereforeadaptedgracefullytovariationsinbandwidth,latency,
jitter,andloss.Theamountofinteractivetrafficwasminimal,
andotherapplicationsrequiringstricterguaranteeswereatan
experimentalstage.
However,anewgenerationofapplicationswithnewservice
requirementsemergedastheInternetgrewinsuccess.The
increasingreachandcapacityoftheInternetmadeitan
attractiveinfrastructuretosupportanincreasingnumberof
applications.Inaddition,corporations,governments,and
educationalinstitutions,amongothers,foundtheIPprotocolan
appealingoptiontobuildtheirprivatedatanetworks.Manyof
thenewIPapplications(forexample,voiceandvideo)hada
real-timenatureandlimitedtolerancetovariationsin
bandwidth,latency,jitter,andloss.Theserviceexpectationsof
networkusersandtheirapplicationrequirementsmadethe
best-effortservicedefinitioninsufficient.
ThedefinitionofaQoSarchitecturestartedinthemiddleofthe
1990s.Sincethen,theInternetEngineeringTaskForce(IETF)
hasdefinedtwoQoSarchitecturesforIP:IntegratedServices
(IntServ)andDifferentiatedServices(DiffServ).TheIntServ
architecturewastheinitialproposedsolution.Subsequently,the
DiffServarchitecturecametolife.MPLSlaterincorporated
supportfortheDiffServarchitecture,whichtheIETFhad


definedexclusivelyforIP.
Thesetwoarchitecturesusedifferentassumptionsandtake
differentapproachestobringingQoStoIP.Althoughsometimes
consideredoppositeandcompetingarchitectures,theytendto
complementeachother.Moreover,theQoSmechanismsused
ultimatelytomanipulatetrafficareessentiallythesameinboth
architectures.

IntegratedServices
TheIntServworkinggroupwasresponsiblefordevelopingthe
specificationsofthisarchitectureattheIETF.Thegroupmetfor
thefirsttimeduringthetwenty-ninthIETFin1994.The
architecturespecificationshaveacloserelationshipwiththe
workoftheIntServoverSpecificLinkLayers(ISSLL)andthe
ResourceReservationProtocol(RSVP)workinggroups.The
ISSLLworkinggroupdefinedtheimplementationofIntServ
overdifferentlink-layerprotocols(forexample,Ethernetand
ATM).TheRSVPworkinggroupdefinedtheRSVPprotocolthat
theIntServgroupselectedasthesignalingprotocol.Thethree
workinggroupscollectivelyproduced32RFCs,ofwhich24are
intheIETFstandardstrack.Theworkinggroupseventually
closedbetweentheyears2000and2002.
TheIETFdecidedtomodifytheoriginalInternetarchitectureto
supportreal-timeapplications.TheIETFconsideredsimpler
alternatives,buttheyofferedless-completesolutions.For
instance
Fair-queuingalgorithmssolvedtheunfairnessbetweendata
andreal-timeapplications,buttheycouldnotguaranteethe
delayandjitter.
Theuseofseparatenetworksforseparateserviceswasless


efficientduetothelowerlevelsofstatisticalmultiplexing.
Bandwidthoverprovisioningwasnotarealisticsolution
whenbandwidthwasofferedasaservice.
Asimpleprioritymechanismcouldnotpreventagrowing
numberofreal-timeflowsfromcausingdegradationofall
flows.
Therateanddelayadaptationofreal-timeapplicationshad
limits,especiallywhennoadmissioncontrolwasused.

IntServTerminology
ThissectionlistsseveralimportanttermsthatIntServ
introduces.Thenexttwosectionsprovidemoredetailabout
theseabstractions:
FlowAnidentifiablestreamofpacketsthatanetworknode
associateswiththesamerequestforQoS.Aflowmayspan
asingleormultipleapplicationsessions.
Trafficspecification(TSpec)Characterizationofthe
trafficpatternofaflowovertime.
Servicerequestspecification(RSpec)Characterization
oftheQoSaflowdesires.
Flowspecification(flowspec)CombinationofaTSpec
andanRSpec.Networknodesusetheflowspecasinputfor
admission-controldecisions.

ArchitecturePrinciples


AcrucialprincipleoftheIntServarchitectureistherequirement
forresourcereservation.Thisrequirementimpliesadmission
controltomanagefiniteresources.IntServnodesneedtoavoid
acceptingunauthorizedrequestsorrequeststhatcanaffect
existingreservationswithservicecommitments.Differenttypes
ofusersareexpectedtohavedifferentrightstoreserve
networkresources.Inaddition,thenetworkloadhastobe
controlledtomeetthequantitativespecificationoftheservicequalitycommitmentsofexistingflows.IntServleavesthe
selectionoftheQoStotheapplicationratherthanthenetwork.
Thearchitecturedefinesaflowasthebasicserviceunit.This
abstractionrepresentsadistinguishablestreamofpacketsthat
requiresthesameQoS.Flowsareunidirectional.Theyhavea
singlesourceandoneormanydestinations.IntServrequires
theuseofper-flowstateinnetworknodes.Thisrequirement
resultsfromtheflowgranularityandtheuseofresource
reservationwithadmissioncontrol.Havingnetworknodes
maintainingper-flowstaterepresentsasignificantchangeto
theoriginalIParchitecturethatleftper-flowstatetoend
systems.Thearchitecturerecommendstheuseofasignaling
protocoltosetupandrefreshthestatetopreservethe
robustnessoftheIPprotocol.RFC1633introducesthe
architecture.Figure1-1showsasimpleexampleofanIntServ
network.

Figure1-1.OverviewofaNetworkImplementing
IntServ

[Viewfullsizeimage]


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