traffic management and control 173-182

173CHAPTER8TRAFCMANAGEMENTANDCONTROL81INTRODUCTIONCOMMUNICATIONSTRAFCMANAGEMENTANDCONTROLISINMANYWAYSSIMILARTOMANAGINGANDCONTROLLINGVEHICULARTRAFCINALARGECITYTHINKOFTHEMAINAVENUESASARTERIALTRAFCBEARINGLINKSTHATBRINGTRAFCVEHICLESANDPEDESTRIANSTOINTERSECTIONSWITHTRAFCLIGHTSINTHISCASE,TRAFCLIGHTSMAYBECONSIDEREDTHEEQUIVALENTOFTRAFCSWITCHINGNODES,WHEREASVEHICLESANDPEDESTRIANSARETHEEQUIVALENTOFPACKETSOFINFORMATIONINCOMMUNICATIONSIFTRAFCLIGHTSAREWELLSYNCHRONIZEDANDTHEYTURNGREENANDREDFORTHECORRECTAMOUNTOFTIMEACCORDINGTOVOLUMEOFVEHICLESORPEDESTRIANSATTHEQUEUES,THENTRAFCFRUSTRATINGJAMSAREELIMINATEDORATLEASTMINIMIZEDBUTHOWDOWECONTROLALLLIGHTSTOACCOMPLISHTHISCURRENTLY,INLARGECITIES,INTELLIGENTCAMERASMONITORTHEOWOFCARSANDTHEQUEUESATTHEINTERSECTIONS,ANDBASEDONATRAFCALGORITHM,LIGHTSCONTROLTHEOWTOMINIMIZEATLEASTINTHEORYCONGESTIONHOWEVER,CURRENTLYTHISREQUIRESHUMANINTERVENTION,ANDITISNOTCOMPLETELYAUTOMATICINFACT,THESCENARIOOFCOMPUTERCONTROLLINGTRAFCLIGHTSHASINSPIREDAHOLLYWOODMOVIETHISCITYTRAFCPARADIGM,ASCOMPLEXASITMAYSEEM,ISMUCHSIMPLERTHANACOMMUNICATIONSSWITCHINGNODE,WHERETHEREAREMANYINPUTANDOUTPUTBERS,EACHBERHASMANYOPTICALCHANNELS,ANDEACHOPTICALCHANNELCARRIESASIGNALEG,OC48,WHICHISTHEMULTIPLEXOFMANYTRIBUTARIESINTHISSCENARIO,SOMESIGNALSMAYNEEDTOBESWITCHEDINTACT,WHEREASSOMEOTHERSNEEDTOBEDEMULTIPLEXEDSINCEDIFFERENTTRIBUTARIESNEEDTOBESWITCHEDTODIFFERENTOUTPUTPORTSMOREOVER,THESIGNALMAYCONTAINSYNCHRONOUSPAYLOADSVOICE,VIDEOANDASYNCHRONOUSIP,ETHERNET,ANDOTHERDATASPECICTHATIS,THEREAREDIFFERENTPROTOCOLSTOBEEXECUTEDANDDIFFERENTREQUIREMENTSSEEFIGS419AND426THUS,SOMEPAYLOADSNEEDTOBESWITCHEDWITHOUTDELAY,WHEREASSOMEOTHERSMAYBETEMPORARILYBUFFEREDWITHSUCHCOMPLEXITY,THECITYTRAFCCONTROLPROBLEMSUDDENLYSEEMSVERYSIMPLECOMPAREDWITHTHECOMMUNICATIONSTRAFCCONTROLBASEDONTHISCOMMUNICATIONSPARADIGM,INDWDMOPTICALNETWORKS,THEREARETWOMAJORMANAGEMENTTYPESONEISCONCERNEDWITHTHEWAVELENGTHMANAGEMENTACROSSTHENETWORKANDTHEOTHERWITHCLIENTBANDWIDTHMANAGEMENTINTHEFOLLOWING,WEASSUMETHATCONTROLMESSAGESTHATAREREQUIREDFORBANDWIDTHMANAGEMENTANDCONNECTIVITYESTABLISHMENTAREACCOMPLISHEDUSINGSPECICMESSAGESANDALGORITHMSBASEDONONEOFTHESEVERALWELLKNOWNMETHODSDISTRIBUTEDORCENTRALIZEDCONTROLANDINCHANNELOROUTOFCHANNELMESSAGESCENTRALIZEDCONTROLIMPLIESTHATALLNODESSENDCONGURATIONANDSTATEMESSAGESTOACENTRALIZEDSYSTEMTHATOVERSEESTHEOPERATIONANDCONNECTIVITYESTABLISHMENTACROSSTHEOVERALLNETWORK,FIG81ALTHOUGHCENTRALIZEDCONTROLISEFCIENT,ANAGREEMENTMUSTEXISTAMONGALLNETWORKOPERATORSIFDIFFERENTONCOMMONNETWORKPARAMETERS,PERFORMANCEOBJECTIVES,ANDPROTOCOLLANGUAGESDISTRIBUTEDCONTROLIMPLIESTHATALLNODESINTHEOVERALLNETWORKPARTAKEINTHENETWORKCONTROL,FIG82THISISACCOMPLISHEDWITHEXTENSIVEPROTOCOLSTONDTHEBESTROUTEINTHENETWORKASWELLSVKARTALOPOULOS,NEXTGENERATIONINTELLIGENTOPTICALNETWORKS,CSPRINGER20081748TRAFCMANAGEMENTANDCONTROLNMSEMS/NMSSTANDARDINTERFACEEMSAEMSBEMSNVENDORSPECIFICORSTANDARDINTERFACENENENENENENENENENEMULTIVENDORNETWORKFIG81CENTRALIZEDCONTROLOFAMULTIVENDORNETWORKENVIRONMENTCONSISTSOFINTERCONNECTEDNETWORKELEMENTSNETHATCOMPRISENETWORKDOMAINS,ANDEACHDOMAINISCONNECTEDWITHTHENETWORKMANAGEMENTSYSTEMNMSVIAELEMENTMANAGEMENTSYSTEMSEMSASTOMANAGETHEHEALTHOFTHENETWORKANDTRAFCEFCIENCYFOREXAMPLE,THEHOPBYHOPROUTEDISCOVERYANDOODINGTHENETWORKARETWOWELLKNOWNALGORITHMS1BECAUSEDISTRIBUTEDCONTROLUSESEXTENSIVEPROTOCOLSANDALGORITHMS,ANAGREEMENTMUSTEXISTAMONGALLNETWORKOPERATORSIFDIFFERENTONCOMMONNETWORKINTERFACEPROTOCOLSANDPERFORMANCEOBJECTIVESINCHANNELMESSAGESAREMESSAGESEMBEDDEDINTHEOVERHEADOFTHESAMECHANNELORPACKETTHATTRANSPORTSCLIENTDATAFOREXAMPLE,INSONET/SDH,SPECICCONTROLMESSAGESFORERRORCONTROLANDPROTECTIONTOSWITCHINGAREINCLUDEDINTHEOVERHEADCONVERSELY,OUTOFCHANNELMESSAGESAREMESSAGESTHATUSESPECICALLYALLOCATEDCHANNELSORPACKETSFOREXAMPLE,THISISTHECASEINATMWHICHUSESSPECICATMCELLSFORCALLADMISSIONCONTROLANDSERVICELEVELAGREEMENTNEGOTIATION,ANDINTHEOTNCASE,ITUSESASEPARATESUPERVISORYCHANNEL,FIG83NETWORKNCISUBNETWORKDOMAINONNINCIONNIOPTNETTONETINTERFACENCINETWORKTOCLIENTINTERFACEFIG82INDISTRIBUTEDCONTROL,ALLNODESPARTAKEINTHEDISCOVERYOFTHEBESTOPTICALROUTEACROSSTHEOVERALLNETWORK,WHICHMAYCONSISTOFSUBNETWORKSORDOMAINS83WAVELENGTHMANAGEMENTFIG83INOTN,OVERHEADINFORMATIONABOUTSECTION,PATH,ANDTANDEMCONNECTIONISTRANSPORTEDWITHANOUTOF175OCHSECTIONOCHTCOPTICALSUPERVISORYCHANNELOSCOCHPATHOCHPAYLOADTRANSPORTEDOVEROTMNTCTANDEMCONNECTIONOCHOVERHEADTRANSPORTEDOVEROSC82CLIENTBANDWIDTHMANAGEMENTCLIENTBANDWIDTHMANAGEMENTISAFUNCTIONTHATISREQUIREDBYALLTYPESOFCOMMUNICATIONSYSTEMSANDNETWORKS,VOICEORDATA,SMALLORLARGETHISFUNCTIONMUSTASSURETHATCLIENTSDATAISDELIVEREDRELIABLY,SECURELY,TIMELY,ANDWITHTHEAGREEDQUALITYOFSERVICE2,REGARDLESSOFTHEMETHODITISTRANSPORTED,NAMELY,BYMEANSOFTRIBUTARYORCONTAINERUNITSASINSYNCHRONOUSTRAFC,ORDIRECTLYMAPPEDORBULKLLEDINTHESYNCHRONOUSPAYLOADSEEFIG210,ORPACKETIZEDANDTRANSPORTEDBYMEANSOFADAPTATIONCLIENTBANDWIDTHMANAGEMENTHASTWOOBJECTIVES1DELIVERTHECLIENTSBANDWIDTHACCORDINGTOSERVICELEVELAGREEMENTANDQUALITYOFSERVICEAND2INCREASETHENETWORKBANDWIDTHEFCIENCYBYLLINGTHEPAYLOADENVELOPEORTHENETWORKBANDWIDTHCAPACITYWITHTHECLIENTDATAASMUCHASPOSSIBLEHOWEVER,ASTRAFCBECOMESMOREELASTIC3,ASTHEAGGREGATEBANDWIDTHDEMANDINCREASES,ASFAULTSANDSEVEREDEGRADATIONSOCCURINNODES,ONBERLINKS,ANDINOPTICALCHANNELS4,TRAFCMANAGEMENTBECOMESMORECHALLENGING83WAVELENGTHMANAGEMENTINMODERNDWDMSYSTEMS,EACHWAVELENGTHOFTHEITUTGRIDISUSEDASASEPARATEOPTICALPATH,ALSOCALLEDALIGHTPATH,WHICHLIKEAHIGHWAYCARRIESMANYCLIENTSIGNALSESTABLISHINGENDTOENDCONNECTIVITYCURRENTLY,THEREARETWOFUNDAMENTALLYDIFFERENTMETHODSFORESTABLISHINGLIGHTWAVECONNECTIVITYTHERSTMETHODCONSIDERSAPATHFORWHICHTHESAMEWAVELENGTHOVERTHEENTIREENDTOENDPATHISASSIGNEDEVENIFTHELIGHTPATHISACROSSSEVERALSUBNETWORKS,EACHMANAGEDBYDIFFERENTNETWORKOPERATORTHISCASEISKNOWNASSINGLEWAVELENGTHPATHCONNECTIVITY,FIG84ALTHOUGHATRSTGLANCETHISMETHODMAYSEEMSIMPLISTIC,INAMULTINODENETWORK,ITISCOMPLEX,ANDITMAYRESULTINWAVELENGTHCONTENTIONORBLOCKINGANDTHUSNETWORKINEFCIENCYTHESECONDMETHODCONSIDERSDIFFERENTWAVELENGTHSTHATARECONCATENATEDOVERACOMPLETEPATHTHISMETHODISNETWORKB2B1SUBNETWORKFIG84AMESHNETWORKMAYESTABLISHCONNECTIVITYDOMAINUSINGTHESAMEWAVELENGTHENDTOENDORMULTIPLECONCATENATEDWAVELENGTHSA1A21768TRAFCMANAGEMENTANDCONTROLKNOWNASMULTIWAVELENGTHPATHCONNECTIVITYTHELATTERMETHODREQUIRESEITHERWAVELENGTHCONVERTERSATEACHNODEORNODESTHATAREOPTICALELECTRICALOPTICALOEOTHISMETHODHASTHEADDEDADVANTAGEOFUTILIZINGDIFFERENTWAVELENGTHSOFTHEITUTGRIDONTHELINKSTHATMAKEUPTHEPATHANDTHUSITINCREASESWAVELENGTHUTILIZATIONANDEFCIENCYHOWEVER,THISMETHODADDSTONODEDESIGNCOMPLEXITYANDCOSTOFCOMPONENTSSUBSTANTIALLY,ANDTHUSTOFAILUREMODES,PROVISIONING,ANDMAINTENANCEWAVELENGTHMANAGEMENTFORTHESINGLEWAVELENGTHPATHCONNECTIVITYMETHODISSIMPLERALTHOUGHLIMITEDANDBANDWIDTHINEFCIENTTHEREASONISTHATTHENETWORKMAYBEUNABLETONDTHESAMEWAVELENGTHFROMSOURCETODESTINATIONFORALLPOSSIBLEROUTESLEADINGTOPOTENTIALWAVELENGTHBLOCKINGFOREXAMPLE,IFWECONSIDERAMESHDWDMNETWORK,THEBLOCKINGPROBABILITYISAFUNCTIONOFTOPOLOGY,NUMBEROFBERSPERNODEANDNUMBEROFWAVELENGTHSOPTICALCHANNELSPERBER,ANDALSONUMBEROFDROPPEDANDADDEDCHANNELSATEACHNODEWEASSUMETHATNODESINAMESHNETWORKAREALSOOPTICALADDDROPMULTIPLEXINGNODESOADMTHUS,ASTHENUMBEROFBERSPERNODEANDWAVELENGTHSPERBERINCREASE,THEPROBABILITYFORBLOCKINGDECREASESTHEKEYOBJECTIVEINTHISCASEISBANDWIDTHEFCIENCY5WAVELENGTHMANAGEMENTFORTHEMULTIWAVELENGTHPATHCONNECTIVITYMETHODISMORECOMPLEXALTHOUGHMOREBANDWIDTHEFCIENTANDBECAUSEOFTHEADDEDHARDWARECOMPLEXITYADDEDWAVELENGTHCONVERTERS,ITISCOSTLIERINTHISCASE,IFWECONSIDERAMESHDWDMNETWORKWITHWAVELENGTHCONVERTERSINEACHNODE,THEBLOCKINGPROBABILITYISAFUNCTIONOFTOPOLOGY,NUMBEROFBERSPERNODEANDNUMBEROFWAVELENGTHSOPTICALCHANNELSPERBER,NUMBEROFDROPPEDANDADDEDCHANNELSATEACHNODE,ANDALSONUMBEROFCONVERTERSINEACHNODETHUS,ASTHENUMBEROFBERSPERNODEANDWAVELENGTHSPERBERINCREASES,THEREQUIREDNUMBEROFCONVERTERSINEACHNODEINCREASES,THEPROBABILITYFORBLOCKINGISALMOSTELIMINATEDALTHOUGHTHECOSTOFTHENETWORKANDWAVELENGTHMANAGEMENTINCREASESDRAMATICALLYASARESULT,THEOBJECTIVEINTHISCASEISTOBALANCEBANDWIDTHEFCIENCYANDOPTIMIZECOSTAHYBRIDMETHODMAYBEUSEDTOACCOMPLISHTHISALLOCATEANUMBEROFWAVELENGTHSTHATPROVIDESINGLEWAVELENGTHCONNECTIVITYOVERSELECTEDPATHSANDALLOCATETHEREMAININGWAVELENGTHSFORTHEMULTIWAVELENGTHCONNECTIVITYPATHMETHODTHISMETHODELIMINATESSEVERALWAVELENGTHCONVERTERS,ANDITSIMPLIESNODEDESIGNANDWAVELENGTHMANAGEMENTACONSEQUENCETHATALSONEEDSTOBEADDRESSEDISPROTECTIONSTRATEGY,ATTHEBERLEVELASWELLASATTHEWAVELENGTHLEVELDUETOSEVEREDEGRADATIONORCOMPONENTHARDFAILUREPROTECTIONMAYBESIMPLEORCOMPLEX,DEPENDINGONTHEADAPTEDPROTECTIONSTRATEGY,11,11,1N,ANDSOONINDWDM,ANOTHERISSUEHASAROSE,NAMELYWAVELENGTHCOLLISIONINTRADITIONALSINGLEWAVELENGTHNETWORKS,WAVELENGTHCOLLISIONHASNOTBEENANISSUESINCETHEOPTICALCHANNELWASONLYONEAT1,310ORAT1,550NMTHUS,MOVINGTHISCHANNELFROMONEBERTOANOTHER,ITWASASTRAIGHTFORWARDOPERATION,ASLONGASAPROTECTIONBERWASAVAILABLEINDWDM,WHEREONESYSTEMINONEDOMAINISINTERCONNECTEDWITHASYSTEMINANOTHERDOMAINWHEREDOMAINSMAYBEOPERATEDBYDIFFERENTNETWORKPROVIDERS,WAVELENGTHCOLLISIONMAYOCCUR,FIG85,WAVELENGTHCONVERSIONISNEEDEDANDALSOWAVELENGTHMANAGEMENTOVERTHECOMPLETEENDTOENDPATHHERE,WAVELENGTHCOLLISIONISDENEDASTHEACTIONBYWHICHONEOPTICALCHANNELASSOCIATEDWITHAPARTICULARWAVELENGTHOVERANETWORKB2B1SUBNETWORKFIG85SOMESAMEWAVELENGTHLIGHTPATHSDOMAINMAYOVERLAPOVERONEORMORELINKSCAUSINGWAVELENGTHCOLLISIONA1A284TRAFCMANAGEMENT177LINKISSWITCHEDFROMLINKATOLINKB,WHEREINLINKBTHESAMEWAVELENGTHISALREADYINUSEFORADIFFERENTPATHTHISDENITIONISEXTENDABLETOMORETHANONEWAVELENGTHASARESULT,ASUBSTANTIALEFFORTHASBEENSPENTTODETERMINETHEBLOCKINGPROBABILITYFORDIFFERENTNETWORKTOPOLOGIES,NODECOMPLEXITIES,ANDTRAFCCHARACTERISTICSANDALSOUNDERSTATICAND/ORDYNAMICCONDITIONSINTHISPURSUE,SEVERALALGORITHMSWEREDEVELOPEDTOESTABLISHTHERULESTHATOPTIMIZEWAVELENGTHASSIGNMENTPROCEDURESANDTHUSTRAFCROUTINGANDNETWORKTHROUGHPUT612831PATHSWITHROADMSWDMOPTICALPOINTTOPOINT,MESHORRINGNETWORKSHAVENODESTHATARECAPABLEOFDROPINGANDADDINGWAVELENGTHS,HENCEKNOWNASOPTICALADDDROPMULTIPLEXINGNODESOADMTHEADDED/DROPPEDWAVELENGTHSCARRYTRAFCTOBEDELIVEREDTOCUSTOMERSATTHELOCATIONOFTHEOADMCURRENTLY,THISISACCOMPLISHEDBYDESIGNATINGAPRIORIWHICHWAVELENGTHSOFTHEGRIDISTOBEDROPPEDASWELLASTHENUMBEROFWAVELENGTHSDEPENDINGONAPPLICATION,FROM1TO4,THISISKNOWNASXEDOADMCONGURABILITYTHENEXTGENERATIONINTELLIGENTNETWORKHOWEVERNEEDSTOBEABLETODROPANDADDEXIBLETRAFC,ANDTHUSOADMNODESNEEDTOBERECONGURABLEASDESCRIBEDIN13THATIS,OADMNODESMUSTBEABLETOBEPROGRAMEDEITHERLOCALLYORREMOTELYANDBEABLETODROPANDADDFROM1TONWAVELENGTHS,ASNEEDARISESSUCHNODESAREKNOWNASRECONGURABLEOADMSROADMHOWEVER,BECAUSEOFTHEDYNAMICNATUREOFRECONGURABILITY,ROADMSNEEDTOBEFAST,RELIABLE,ANDVERIABLEWESHOULDALSOPOINTOUTTHATMESHNETWORKSWITHROADMSADDANADDITIONALLEVELOFCOMPLEXITYONTHEPATHORROUTENDINGALGORITHMSBECAUSEWAVELENGTHSTHATAREAVAILABLEFORESTABLISHINGCONNECTIVITYMAYHAVETOBEUSEDBYROADMSANDTHUSTHENUMBEROFWAVELENGTHSFORENDTOENDCONNECTIVITYNEEDTOBERECALCULATEDADDITIONALLY,RECONGURABILITYADDSTONODEDESIGNCOMPLEXITYBECAUSECERTAINRECONGURABLEORREASSIGNEDWAVELENGTHSAREDROPPEDANDADDEDINSTEADOFCONTINUINGTHROUGHORVICEVERSATHUS,THISMAYREQUIREOPTICALPOWERBUDGETRECALCULATIONANDWAVELENGTHEQUALIZATIONANDDISPERSIONCOMPENSATIONANOTHERNODECOMPLEXITYISADDEDIFATTHEROADMCERTAINWAVELENGTHSAREREASSIGNEDTOBEDROPPEDANDADDEDINORDERTOCARRYMULTIPLEXEDTRAFCSUCHASSONET/SDH,INWHICHSOMEVTSNEEDTOPASSTHROUGHHOWEVER,THISISSIMPLIEDIFTRAFCISPACKETIZEDOPTIMIZINGTRAFCEFCIENCYFORDIFFERENTTRAFCTYPESISTHESUBJECTOFCURRENTRESEARCH84TRAFCMANAGEMENTTRAFCMANAGEMENTISRELATEDTOCLIENTTRAFCANDTHEREFORE,ALTHOUGHRELATEDTOBANDWIDTHMANAGEMENT,HASMORESPECICTASKSTOPERFORMFOREXAMPLE,ALTHOUGHBANDWIDTHMANAGEMENTADDRESSESTHEDISTRIBUTIONOFTRAFCEVENLYOVERNETWORK,ALSOKNOWNASBANDWIDTHBALANCING,TRAFCMANAGEMENTISMORECONCERNEDWITHCLIENTTRAFCSOTHATITMEETSTHEEXPECTEDQUALITYOFSERVICE,EXPECTEDREALTIMEDELIVERY,ANDALSOCLIENTBANDWIDTHONDEMANDTRAFCMANAGEMENTASSURESTHATINCOMINGTRAFCISMONITORED,ITISPROPERLYCONNECTED,ANDITSQUALITYLEVELISMAINTAINEDTHISISACCOMPLISHEDBYPOLICINGINCOMINGCLIENTTRAFCATTHEEDGENODESASACONSEQUENCE,TRAFCPOLICINGREQUIRESCONTINUOUSMONITORINGFORTRAFCPARAMETERCOMPLIANCEWITHTHESERVICELEVELAGREEMENTSLA,ASWELLASMONITORINGFORCONNECTIONPARAMETERVIOLATIONS,ANDUSEREQUIPMENTMALFUNCTIONING,AFUNCTIONKNOWNINATMASCONNECTIONMONITORINGTHEATMFORUMANDTHEITUTHAVEDENEDPARAMETERSTOMAINTAINTHEAGREEDTRAFCQOSITHASALSODENEDALGORITHMSFORPOLICINGTHETRAFCATTHEUSERNETWORKINTERFACEUNIFORBOTHCONSTANTBITRATECBRANDVARIABLEBITRATEVBRTHISALGORITHMISKNOWNASTHEGENERICCELL1788TRAFCMANAGEMENTANDCONTROLRATEALGORITHMGCRATHEGCRAISIMPLEMENTEDWITHTHECONTINUOUSSTATELEAKYBUCKETANDITISBASEDONTWOPARAMETERSTHEINCREMENTIANDTHELIMITLTHEIPARAMETERAFFECTSTHECELLRATETHELPARAMETERAFFECTSTHECELLBURSTFOREXAMPLE,THEPARAMETERSUTILIZEDINATMFORTRAFCMANAGEMENTAREPEAKCELLRATEPCRFORCBRANDVBRCONNECTIONS,SUSTAINABLECELLRATESCRFORVBRCONNECTIONS,ANDMAXIMUMBURSTSIZEMBSFORVBRCONNECTIONSTHESEPARAMETERSAREPROVIDEDBYTHEUSERDURINGTHECONNECTIONADMISSIONCONTROLCACATUNIINADDITION,THEBURSTTOLERANCEBTPARAMETERPUTSARESTRICTIONONTHEADDITIONALTRAFCABOVETHESCR,BEFOREITISTAGGEDEXCESSIVETRAFC85CONGESTIONMANAGEMENTFAILURESANDSEVERECOMPONENTDEGRADATIONSCANBESTATISTICALLYPREDICTABLEACCORDINGTOMANUFACTURERSFAILUREINTIMEFITDATAHOWEVER,THEREAREALSOUNPREDICTABLEFAILURES,SUCHASBERCUTSEITHERWAY,FAILURESANDDEGRADATIONSCAUSESTATISTICALUCTUATIONSOFTRAFCOWINTHENETWORKINANATTEMPTTOBYPASSTHEFAULTTHUS,THEREISANITEPROBABILITYTHATTRAFCTHROUGHANODEORLINKREACHESTHEMAXIMUMCAPACITYESTABLISHINGACONGESTIONCONDITIONMANIFESTEDBYNODEORLINKOVERLOAD,BANDWIDTHLOST,OREVENNETWORKCRASHINGENERAL,CONGESTIONMANAGEMENTISDENEDASANETWORKELEMENTSTATEUNABLETOMEETTHENEGOTIATEDNETWORKPERFORMANCEANDQUALITYOFSERVICEQOSOBJECTIVESASSUCH,CONGESTIONMANAGEMENTISSERIOUSLYADDRESSEDINDWDM,CONGESTIONMANAGEMENTISVERYIMPORTANTBECAUSESEVERELYDEGRADEDCOMPONENTSORFAULTYNODESANDLINKSAFFECTAHUMONGOUSAMOUNTOFTRAFCTHEREFORE,TRAFCREROUTINGNEEDSTOBEEXECUTEDEXPEDIENTLYANDEFCIENTLYTHUS,CONGESTIONMANAGEMENTNEEDSTOCONSIDERTHETYPEOFFAULTASEACHFAULTINUENCESBANDWIDTHOWATADIFFERENTLEVEL,TYPESOFSERVICESSUPPORTEDBYTHENETWORKASEACHTRAFCTYPEHASDIFFERENTREQUIREMENTS,NETWORKTOPOLOGYASEACHTOPOLOGYHASDIFFERENTSERVICESURVIVABILITYCHARACTERISTICS,SIZEOFNETWORK,INBOTHBANDWIDTHCAPACITYANDNUMBEROFNODES,ANDINTERNETWORKINGASTHEOVERALLPATHMAYCROSSSEVERALNETWORKPROVIDERDOMAINS,EACHCONSISTINGOFNODESWITHDIFFERENTSYSTEMCAPABILITIES86ROUTINGALGORITHMSINDWDMOPTICALNETWORKS,ALIGHTPATHCONNECTSASOURCEWITHADESTINATIONANDITMAYCONSISTOFTHESAMEWAVELENGTHFROMONEENDTOTHEOTHERENDORITMAYCONSISTOFSEVERALCONCATENATEDWAVELENGTHS,WHEREBYAWAVELENGTHCHANGESTOANOTHERBYMEANSOFWAVELENGTHCONVERTERSAMESHNETWORKWITHMANYNODESHASALARGENUMBEROFPOSSIBLESOURCETODESTINATIONPATHSADWDMMESHTOPOLOGYMAYBETHOUGHTASTHESUPERPOSITIONOFMANYMESHSINGLEWAVELENGTHTOPOLOGIESINDWDMOPTICALMESHNETWORKS,ONEPATHMAYOVERLAPWITHANOTHERPATHOVERONEORMORELINKSTHISMAKESTHEROUTINGALGORITHMMORECOMPLEXASTHESAMEWAVELENGTHFROMTWODIFFERENTSOURCESCANNOTCOEXISTOVERTHESAMEBERLINKIFTHISOCCURS,CROSSTALKSEVERELYDEGRADESTHETWOCHANNELSSOMESOLUTIONSUSEPOLARIZATIONSTATESTOMINIMIZECROSSTALKBUTTHELINKMUSTBEABLETOMAINTAINTHETWOPOLARIZATIONSTATESOVERITSFULLLENGTHTHUS,ATSETUPTIME,THEREISANITEPROBABILITYOFWAVELENGTHBLOCKING,PARTICULARLYWHENWAVELENGTHSAREDYNAMICALLYASSIGNEDINORDERTOMINIMIZETHEBLOCKINGPROBABILITYEFCIENTLY,OPTICALNODESREQUIRESPECICCONGURATION17987DISCOVERYOFOPTICALNETWORKTOPOLOGYFEATURES,WAVELENGTHCONVERSIONSTRATEGY,ANDSWITCHINGCAPABILITIESTHISISACCOMPLISHEDWITHTHEUSEOFROUTINGANDWAVELENGTHASSIGNMENTRWAALGORITHMSRWAALGORITHMSARECLASSIEDASSTATICANDDYNAMIC14DYNAMICRWAALGORITHMSASSIGNANDREMOVELIGHTPATHSRANDOMLYACCORDINGTONETWORKCONNECTIONREQUESTS,TRAFCUTILIZATION,ANDCONGESTIONSTATESTOINCREASENETWORKBANDWIDTHPERFORMANCE,ANODEADVERTISESITSSTATUSANDWAVELENGTHAVAILABILITYTOOTHERNODESBYMEANSOFPACKETSSUCHASADDRESSABLE,SHARED,CHANNELIZED,ANDHYBRIDTHISINCLUDESGLOBALNETWORKSTATEPARAMETERSONLINKSWITHINTHENETWORK,ASWELLASLOCALNODESTATUSTWODYNAMICROUTINGALGORITHMSARETHEALTERNATEPATHROUTINGANDUNCONSTRAINEDPATHROUTINGALTERNATEPATHROUTINGASSUMESTHATEVERYNODESTORESTHERSTNSHORTESTANDPREDETERMINEDPATHSTOEACHDESTINATIONBYUTILIZINGGLOBALANDLOCALNODELINKINFORMATIONCONGESTIONISDETERMINEDINPARTBYTHENUMBEROFWAVELENGTHSAVAILABLEPERPATHORLINKUNCONSTRAINEDROUTINGCONSIDERSALLPATHS,ANDITISBASEDONTHECOSTFUNCTIONOFALLLINKSWITHINTHENETWORKTODETERMINETHEOPTIMALENDTOENDPATHINGENERAL,DYNAMICROUTINGALGORITHMSPROCESSGLOBALNETWORKSTATEINFORMATIONTODETERMINETHEENDTOENDPATHALTERNATIVELY,THEDEECTIONORALTERNATEROUTINGALGORITHMISLIMITEDTOSTATEINFORMATIONFROMNEIGHBORINGNODESONLY,INWHICHCASELINKSARECHOSENONAHOPBYHOPBASISACCORDINGTOIT,ATEACHINTERMEDIATENODE,ACONTROLMESSAGEISPROCESSEDBEFOREBEINGFORWARDEDTOTHENEXTNODETHISCONTINUESONEHOPATATIMEUNTILTHEDESTINATIONNODECOMPLETESTHENALPROCESSOFTHECONTROLMESSAGEANDSENDSITBACKTOTHESOURCENODEDECISIONSONWAVELENGTHASSIGNMENTAREBASEDONTHESHORTESTPATHRST,FOLLOWEDBYALTERNATIVEROUTECONSIDERATIONSIFASPECICWAVELENGTHISUNAVAILABLETHELEASTCONGESTEDDEECTIONROUTINGSCHEMECHOOSESFROMALISTOFOUTGOINGLINKSBASEDONTHELARGESTNUMBEROFFEASIBLEWAVELENGTHSTHESHORTESTPATHRSTMETHODRESULTSINLOWERBLOCKINGWITHLESSTRAFCWHILEALEASTCONGESTEDPOLICYRESULTSINLOWERBLOCKINGATHEAVIERTRAFCLOADSTHOSEROUTINGSCHEMESAREAPPLICABLETOSINGLEBERMESHTOPOLOGY,ASWELLASMULTIBERNETWORKS87DISCOVERYOFOPTICALNETWORKTOPOLOGYWAVELENGTHASSIGNMENTALGORITHMSPROVIDETHEOPTIMALWAVELENGTHCONNECTIVITYTOACONNECTIONREQUESTWAVELENGTHASSIGNMENTISCLASSIEDASSTATICANDDYNAMICFORSTATICWAVELENGTHASSIGNMENT,ASEQUENTIALGRAPHCOLORINGAPPROACHISUSEDTONDTHEMINIMUMWAVELENGTHSCOLORSFOROVERAPATHFORTHEOPTICALNETWORKTOROUTEOPTICALCHANNELS,THEPHYSICALANDTHELOGICALLAYERTOPOLOGYOFTHENETWORKMUSTBEKNOWNTHATIS,EACHSWITCHINGNODEMUSTKNOWTHECHARACTERISTICSOFTHEADJACENTSWITCHINGNODESASWELLASTHEINTERCONNECTEDPORTSAMONGADJACENTSWITCHINGNODESTYPICALLY,THISISACCOMPLISHEDWITHSELFDISCOVERYPROTOCOLSSUCHPROTOCOLSUSESIGNALINGMESSAGESTHATLEARNANDSHARENODECONGURATIONANDTRAFCINFORMATIONUSINGSIGNALINGMESSAGES,APROTOCOLENABLESTHENODESTOESTABLISHANDMAINTAINANADJACENCYDATABASETHATREECTSTHESTATEOFTHENETWORKABOUTANODETHESEDATABASESAREREFRESHEDWHENEVERACHANGEINT